Sivakumar Pasupathi - Academia.edu (original) (raw)

Papers by Sivakumar Pasupathi

Research paper thumbnail of Fuel Cell Power Pack with Integrated Metal Hydride Hydrogen Storage for Powering Electric Forklift

Lecture notes in electrical engineering, 2022

Research paper thumbnail of Design and performance simulation of coupled electrolyzer-metal hydride hydrogen compressor system as a part of hydrogen refueling station

Metal hydrides have shown to play an important role in the "hydrogen economy" infrastru... more Metal hydrides have shown to play an important role in the "hydrogen economy" infrastructure for various applications including hydrogen/thermal energy storage systems, hydrogen compression, etc. The deployment of hydrogen-powered electric vehicles is hampered by many challenges including on-board hydrogen storage and hydrogen refueling. As an example, hydrogen refueling stations (HRS) stand as the most complex system in the hydrogen infrastructure pathway. An HRS comprises of two main components: a hydrogen production and a hydrogen compression device to provide hydrogen to end-users at high pressure. Although there are many hydrogen production methods, hydrogen production via water electrolysis is the most promising option. However, water electrolysis becomes cost-effective only if high-grade energy (electricity) is provided by an excess, renewable and free source (Solar PV, wind turbine). On the other side, the hydrogen compression is also a conundrum in HRS design and ...

Research paper thumbnail of Fuel cell power module for an electric forklift with integrated metal hydride hydrogen storage system

Fuel Cell Seminar & Energy Exposition, November 5-7, 2019, Long Beach, USA (poster)

Research paper thumbnail of Enhanced performance of high temperature polymer electrolyte membrane fuel cell using a novel dual catalyst layer structured cathode

Journal of the Taiwan Institute of Chemical Engineers, 2021

Abstract Background High cost is a main barrier of commercialization for high temperature polymer... more Abstract Background High cost is a main barrier of commercialization for high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). Thus, enhancing the efficiency of platinum (Pt) utilization and improving the performance of HT-PEMFC is expected to promote its commercialization. Methods A novel cathode with dual catalyst layer (DCL) structure is designed for enhancing the performance of HT-PEMFC. The catalyst is mainly distributed in outer CL (next to membrane) to concentrate Pt, while a small amount of catalyst is used in inner CL (close to gas diffusion layer). High-Pt-content catalysts (40, 50 wt% Pt/C) and low-Pt-content catalysts (10, 20 wt% Pt/C) are utilized in outer and inner CLs, respectively, to maintain the same thicknesses of two CLs. Significant findings 2/4-DCL gas diffusion electrode (GDE) with an outer CL consists of 40 wt% Pt/C and an inner CL consists of 20 wt% Pt/C shows the highest performance among prepared DCL structured GDEs, which also shows a significantly higher performance than the conventional single CL structured GDEs due to the novel structure of DCL. Finally, a good durability of 2/4-DCL GDE indicates the feasibility in practical HT-PEMFC.

Research paper thumbnail of Control strategy of a fuel-cell power module for electric forklift

International Journal of Hydrogen Energy, 2021

h i g h l i g h t s Lift truck simulation model with hybrid power pack is developed. PEMFC-Batter... more h i g h l i g h t s Lift truck simulation model with hybrid power pack is developed. PEMFC-Battery hybrid model for lift truck application was analyzed. Real lift truck load cycle was simulated.

Research paper thumbnail of HYDRIDE4MOBILITY: An EU HORIZON 2020 project on hydrogen powered fuel cell utility vehicles using metal hydrides in hydrogen storage and refuelling systems

International Journal of Hydrogen Energy, 2021

h i g h l i g h t s Advanced metal hydrides for H storage and compression were proposed. MH conta... more h i g h l i g h t s Advanced metal hydrides for H storage and compression were proposed. MH containers with improved H charge-discharge dynamic performance. Integrated with PEM fuel cell hydrogen energy system was developed. EU Horizon 2020 RISE project 778307 project HYDRIDE4MOBILITY. Hydrogen powered forklift uses MH based H storage and PEM fuel cell.

Research paper thumbnail of A Comprehensive Thermoelectric Cooler (TEC) Modelling

SSRN Electronic Journal, 2020

Faced with the ongoing energy and electricity crises in South Africa and by extension Africa, thi... more Faced with the ongoing energy and electricity crises in South Africa and by extension Africa, this paper presents a comprehensive model of Thermo-Electric Cooler (TEC), in a bid to devise an innovative renewable energy cooler to serve as an efficient heat pump, in which a low DC power source can be applied to it to generate cold, thereby decreasing the total power consumption. The novelty brought forward is an original simulated TEC model in MatLab / Simulink that can easily be configured with respect to a given DC source and thermal load, to determine a TEC optimal operational parameters to increase its heat absorption (cooling power Qc) capacity and as well its coefficient of performance (CoP).

Research paper thumbnail of Effect of Accelerated Stress Testing on High Temperature Proton Exchange Membrane Fuel Cell

ECS Meeting Abstracts, 2017

The durability of high temperature proton exchange membrane (HT-PEM) fuel cells is very important... more The durability of high temperature proton exchange membrane (HT-PEM) fuel cells is very important for its long term performance and commercialization. Commercialization demands progress, especially in the development of fuel cell catalyst materials and carbon supports. The role of platinum and carbon in the catalytic layer are crucial for the stable performance of a fuel cell. Potential cycling is used to evaluate the stability of platinum and carbon support material of catalyst layer. Fuel cells operated under cycling conditions have lower durability than those operated under steady state conditions. The aim of this work is to study degradation of phosphoric acid doped polybenzimidazole membrane based fuel cell under accelerated potential cycling conditions. Potential cycling degrades fuel cell performance. Understanding this degradation related issues associated with potential cycling is necessary to improve the durability of HT-PEM fuel cell. The fuel cell is cycled between open ...

Research paper thumbnail of Facile Preparation of a Surface-Enriched Pt Layer Over Pd/C as an Efficient Oxygen Reduction Catalyst With Enhanced Activity and Stability

Journal of Electrochemical Energy Conversion and Storage, 2020

Pt-enriched surface layer formation on Vulcan carbon-supported Pd (Pt@Pd/C) was successfully prep... more Pt-enriched surface layer formation on Vulcan carbon-supported Pd (Pt@Pd/C) was successfully prepared through a simple and one-pot formic acid reduction approach without any stabilizing agent. The electrocatalytic performance of Pt@Pd/C catalyst toward an oxygen reduction reaction (ORR) in alkaline medium was studied and also compared with standard carbon-supported Pt (Pt/C) and Pd (Pd/C) catalysts. The Pt@Pd/C exhibits higher electrochemical active surface area (74.7 m2/g) and mass activity (1.38 mA/µg) than Pt/C, Pd/C, and contending with standard reported catalysts. In durability tests, Pt@Pd/C showed negligible loss of intrinsic activity (∼10%) after 10,000 cycles which confirmed improved stability than Pt-based catalysts for ORR in KOH medium. This improved electrocatalytic performance could be attributed to their structural characteristics of the Pt-enriched surface layer on Pd/C-core and the compressive lattice strain on Pt. The present investigation demonstrates the simple p...

Research paper thumbnail of PEMFC for aeronautic applications: A review on the durability aspects

Open Engineering, 2017

Proton exchange membrane fuel cells (PEMFC) not only offer more efficient electrical energy conve... more Proton exchange membrane fuel cells (PEMFC) not only offer more efficient electrical energy conversion, relative to on-ground/backup turbines but generate by-products useful in aircraft such as heat for ice prevention, deoxygenated air for fire retardation and drinkable water for use on-board. Consequently, several projects (e.g. DLR-H2 Antares and RAPID2000) have successfully tested PEMFC-powered auxiliary unit (APU) for manned/unmanned aircraft. Despite the progress from flying PEMFC-powered small aircraft with 20 kW power output as high as 1 000 m at 100 km/h to 33 kW at 2 558 m, 176 km/h [1, 2, 3], durability and reliability remain key challenges. This review reports on the inadequate understanding of behaviour of PEMFC under aeronautic conditions and the lack of predictive methods conducive for aircraft that provide real-time information on the State of Health of PEMFCs.Highlights: The main research findings are–To minimize performance loss due to high altitude and inclination ...

Research paper thumbnail of Ex-Situ Electrochemical Characterization of IrO2 Synthesized by a Modified Adams Fusion Method for the Oxygen Evolution Reaction

Catalysts, 2019

The development of highly stable and active electrocatalysts for the oxygen evolution reaction (O... more The development of highly stable and active electrocatalysts for the oxygen evolution reaction (OER) has attracted significant research interest. IrO2 is known to show good stability during the OER however it is not known to be the most active. Thus, significant research has been dedicated to enhance the activity of IrO2 toward the OER. In this study, IrO2 catalysts were synthesized using a modified Adams fusion method. The Adams fusion method is simple and is shown to directly produce nano-sized metal oxides. The effect of the Ir precursor salt to the NaNO3 ratio and the fusion temperature on the OER activity of the synthesized IrO2 electrocatalysts, was investigated. The OER activity and durability of the IrO2 electrocatalysts were evaluated ex-situ via cyclic voltammetry (CV), chronopotentiometry (CP), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). Physical properties of the IrO2 electrocatalysts were evaluated via X-ray diffraction (XRD), transm...

Research paper thumbnail of Dual-shelled Cu2O@Cu9S5@MnO2 hollow spheres as advanced cathode material for energy storage

Journal of Alloys and Compounds, 2019

‡ Miaomiao Cao and Hui Wang contributed equally. Abstract： ： ： ：In this study, dual-shelled Cu 2 ... more ‡ Miaomiao Cao and Hui Wang contributed equally. Abstract： ： ： ：In this study, dual-shelled Cu 2 O@Cu 9 S 5 @MnO 2 hollow spheres with high surface area and porosity are developed as cathode material for electrochemical energy storage. Initially, Cu 2 O spheres are prepared via a hydrothermal method, which act as templates for subsequent procedure of forming hollow spheres with core(Cu 2 O)-shell(Cu 9 S 5) structure. Subsequently, porous MnO 2 shells is deposited on Cu 2 O@Cu 9 S 5 hollow spheres to form dual-shelled hollow spheres. In alkaline

Research paper thumbnail of Hydrogen refuelling station with integrated metal hydride compressor: Layout features and experience of three-year operation

International Journal of Hydrogen Energy, 2019

Research paper thumbnail of Achieving high Pt utilization and superior performance of high temperature polymer electrolyte membrane fuel cell by employing low-Pt-content catalyst and microporous layer free electrode design

Journal of Power Sources, 2019

• GDEs with low Pt loadings are developed for HT-PEMFC. • Combining low-Pt-content catalyst and M... more • GDEs with low Pt loadings are developed for HT-PEMFC. • Combining low-Pt-content catalyst and MPL-free structure is a way to reduce Pt use. • The Pt loading can be lowered to 0.2 mg cm −2 and still with satisfactory performance. • Ultra-low Pt loading can be expected from this strategy by enhancing CL quality.

Research paper thumbnail of Development of a Portable Polymer Electrolyte Membrane Fuel Cell System Using Metal Hydride as the Hydrogen Storage Medium

ECS Transactions, 2016

This paper describes the development of a Portable Polymer Electrolyte Membrane Fuel Cell / PEMFC... more This paper describes the development of a Portable Polymer Electrolyte Membrane Fuel Cell / PEMFC system that was developed at HySA Systems Competence Centre. The system has a rated peak output power of 130W at 240Vac and 5Vdc USB output power. Hydrogen is supplied from Metal Hydride (MH) hydrogen storage canister which uses multi-component AB2 – type hydrogen storage hydride alloy. The in-house developed MH canister was made up of stainless steel tube with external aluminium fins and had a maximum hydrogen storage capacity of 90 NLH2. The improvement of H2 discharge dynamic performance of the MH bed, which is cooled down in the course of H2 desorption, was achieved by the placement of the MH canister in front of exhaust of air cooling system of the PEMFC stack. By the utilisation of the PEMFC waste heat, in combination with the external fins (increase of heat exchange area) and compacting the MH material with Thermal Expanded Graphite / TEG (improvement of the effective thermal con...

Research paper thumbnail of Oxygen reduction reaction on Pt-Pd catalysts supported on carbon xerogels: Effect of the synthesis method

International Journal of Hydrogen Energy, 2018

In this work, Pt-Pd nanoparticles supported on carbon xerogels (Pt-Pd/CX) were synthesised employ... more In this work, Pt-Pd nanoparticles supported on carbon xerogels (Pt-Pd/CX) were synthesised employing unusual routes, in order to evaluate its activity toward the oxygen reduction reaction (ORR). The synthesis methods produced materials with the planned composition (metal content close to 40 wt % and Pt:Pd atomic ratios around 1:2), with Pt, Pd and alloyed Pt-Pd nanoparticles well dispersed on the carbon support. The content of Pt in the nanoparticles was optimised through these procedures, placing this metal at the surface. As a consequence, the Pt-Pd/CX catalysts displayed high activity toward the ORR and remarkable resistance to corrosion, overcoming the electrocatalytic properties of a commercial Pt/C catalyst. Moreover, these catalysts involve four electrons in the ORR. Therefore, the study here presented indicated that the as-synthesised Pt-Pd/CX catalysts are suitable candidates to be employed as cathodes in proton exchange membrane fuel cells.

Research paper thumbnail of A concept of combined cooling, heating and power system utilising solar power and based on reversible solid oxide fuel cell and metal hydrides

International Journal of Hydrogen Energy, 2018

In energy systems, multi-generation including co-generation and tri-generation has gained tremend... more In energy systems, multi-generation including co-generation and tri-generation has gained tremendous interest in the recent years as an effective way of waste heat recovery. Solid oxide fuel cells are efficient power plants that not only generate electricity with high energy efficiency but also produce high quality waste heat that can be further used for hot and chilled water production. In this work, we present a concept of combined cooling, heating and power (CCHP) energy system which uses solar power as a primary energy source and utilizes a reversible solid oxide fuel cell (R-SOFC) for producing hydrogen and generating electricity in the electrolyser (SOEC) and fuel cell (SOFC) modes, respectively. The system uses "high temperature" metal hydride (MH) for storage of both hydrogen and heat, as well as "low temperature" MH's for the additional heat management, including hot water supply, residential heating during winter time, or cooling/air conditioning during summer time. The work presents evaluation of energy balances of the system components, as well as heat-and-mass transfer modelling of MH beds in metal hydride hydrogen and heat storage system (MHHS; MgH 2), MH hydrogen compressor (MHHC; AB 5 ; A ¼ La þ Mm, B] Ni þ Co þ Al þ Mn) and MH heat pump (MHHP; AB 2 ; A ¼ Ti þ Zr, B]Mn þ Cr þ Ni þ Fe). A case study of a 3 kWe R-SOFC is analysed and discussed. The results showed that the energy efficiencies are 69.4 and 72.4% in electrolyser and fuel cell modes, respectively. The round-trip COP's of metal hydride heat management system (MHHC þ MHHP) are close to 40% for both heating and cooling outputs. Moreover, the tri-generation leads to an improvement of 36% in round-trip energy efficiency as compared to that of a stand-alone R-SOFC.

Research paper thumbnail of Eliminating micro-porous layer from gas diffusion electrode for use in high temperature polymer electrolyte membrane fuel cell

Journal of Power Sources, 2017

In this work, we report a simple strategy to improve the performance of high temperature polymer ... more In this work, we report a simple strategy to improve the performance of high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) by eliminating the micro-porous layer (MPL) from its gas diffusion electrodes (GDEs). Due to the absence of liquid water and the general use of high amount of catalyst, the MPL in a HT-PEMFC system works limitedly. Contrarily, the elimination of the MPL leads to an interlaced micropore/macropore composited structure in the catalyst layer (CL), which favors gas transport and catalyst utilization, resulting in a greatly improved single cell performance. At the normal working voltage (0.6 V), the current density of the GDE eliminated MPL reaches 0.29 A cm −2 , and a maximum power density of 0.54 W cm −2 at 0.36 V is obtained, which are comparable to the best results yet reported for the HT-PEMFCs with similar Pt loading and operated using air. Furthermore, the MPL-free GDE maintains an excellent durability during a preliminary 1,400 hour HT-PEMFC operation, owing to its structure advantages, indicating the feasibility of this electrode for practical applications.

Research paper thumbnail of Enhanced Intrinsic Activity and Stability of Au–Rh Bimetallic Nanostructures as a Supportless Cathode Electrocatalyst for Oxygen Reduction in Alkaline Fuel Cells

ACS Sustainable Chemistry & Engineering, 2016

The electroreduction of dioxygen on supportless Au-Rh bimetallic nanostructures (Au-Rh 33 NC) syn... more The electroreduction of dioxygen on supportless Au-Rh bimetallic nanostructures (Au-Rh 33 NC) synthesized by a surfactant template-free, single step chemical reduction method occurred 34 with high intrinsic activity in an alkaline medium. Cyclic voltammetry and linear scan 35 voltammetry together with X-ray diffraction and high-resolution electron microscopy showed that the improved performance of the Au-Rh NC towards dioxygen reduction could be due to the 37 synergistic electronic effects of nano-bimetallic combination and its cluster-like morphology. 38 The electrochemically active surface area (ECSA) was estimated to be 37.2 m 2 g-1 for 39 supportless Au-Rh NC with a 3:1 atomic composition, which was higher than that reported for 40 Ag-based nanocatalysts. The intrinsic activities (IA) of the supportless and carbon supported Au-41 Rh (3:1) NCs were 3.25 and 3.0 mA/cm 2 , respectively, which were higher than those of the 42 standard Pt/C (0.1 mA/cm 2) 45 Au/C catalysts for the oxygen reduction reaction (ORR). Oxygen 43 reduction on both catalysts followed a direct four electron pathway. The accelerated durability 44 test carried out by continuous potential cycling showed that the 3:1 ratio of Au-Rh 45 nanostructures had excellent stability with a 20% increase in ECSA after 10000 potential cycles, 46 highlighting their potential application for real systems.

Research paper thumbnail of Pt3M (M: Co, Ni and Fe) Bimetallic Alloy Nanoclusters as Support-Free Electrocatalysts with Improved Activity and Durability for Dioxygen Reduction in PEM Fuel Cells

Electrocatalysis, 2016

Pt 3 M (M: Co, Ni and Fe) bimetallic alloy nanoclusters were synthesized by a novel and simple ch... more Pt 3 M (M: Co, Ni and Fe) bimetallic alloy nanoclusters were synthesized by a novel and simple chemical reduction approach, and employed as the promising electrocatalyst to accelerate the kinetics of oxygen reduction reaction (ORR) for polymer electrolyte membrane fuel cells. From XRD, the positive shift of diffraction angle confirms the alloy formation between Pt and M and the elemental composition was confirmed by energy dispersive X-ray spectroscopy analysis. The nanocluster morphology and particle size was determined using scanning and transmission electron microscopy analysis. The ORR kinetic parameters for Pt-M electrocatalysts were calculated and compared with reported Pt/C catalysts. Among the Pt-M electrocatalysts, Pt-Co was found to be the most efficient catalyst having the higher mass and specific activity (at 0.9 V vs. RHE) of 0.44 mA/μg and 0.69 mA/cm 2 , respectively. The accelerated durability test reveals that the Pt-M bimetallic alloy nanoclusters retain appreciable surface area and mass activity after 8000 potential cycles confirms good long-term durability, and also competing with the reported benchmark ORR catalysts.

Research paper thumbnail of Fuel Cell Power Pack with Integrated Metal Hydride Hydrogen Storage for Powering Electric Forklift

Lecture notes in electrical engineering, 2022

Research paper thumbnail of Design and performance simulation of coupled electrolyzer-metal hydride hydrogen compressor system as a part of hydrogen refueling station

Metal hydrides have shown to play an important role in the "hydrogen economy" infrastru... more Metal hydrides have shown to play an important role in the "hydrogen economy" infrastructure for various applications including hydrogen/thermal energy storage systems, hydrogen compression, etc. The deployment of hydrogen-powered electric vehicles is hampered by many challenges including on-board hydrogen storage and hydrogen refueling. As an example, hydrogen refueling stations (HRS) stand as the most complex system in the hydrogen infrastructure pathway. An HRS comprises of two main components: a hydrogen production and a hydrogen compression device to provide hydrogen to end-users at high pressure. Although there are many hydrogen production methods, hydrogen production via water electrolysis is the most promising option. However, water electrolysis becomes cost-effective only if high-grade energy (electricity) is provided by an excess, renewable and free source (Solar PV, wind turbine). On the other side, the hydrogen compression is also a conundrum in HRS design and ...

Research paper thumbnail of Fuel cell power module for an electric forklift with integrated metal hydride hydrogen storage system

Fuel Cell Seminar & Energy Exposition, November 5-7, 2019, Long Beach, USA (poster)

Research paper thumbnail of Enhanced performance of high temperature polymer electrolyte membrane fuel cell using a novel dual catalyst layer structured cathode

Journal of the Taiwan Institute of Chemical Engineers, 2021

Abstract Background High cost is a main barrier of commercialization for high temperature polymer... more Abstract Background High cost is a main barrier of commercialization for high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). Thus, enhancing the efficiency of platinum (Pt) utilization and improving the performance of HT-PEMFC is expected to promote its commercialization. Methods A novel cathode with dual catalyst layer (DCL) structure is designed for enhancing the performance of HT-PEMFC. The catalyst is mainly distributed in outer CL (next to membrane) to concentrate Pt, while a small amount of catalyst is used in inner CL (close to gas diffusion layer). High-Pt-content catalysts (40, 50 wt% Pt/C) and low-Pt-content catalysts (10, 20 wt% Pt/C) are utilized in outer and inner CLs, respectively, to maintain the same thicknesses of two CLs. Significant findings 2/4-DCL gas diffusion electrode (GDE) with an outer CL consists of 40 wt% Pt/C and an inner CL consists of 20 wt% Pt/C shows the highest performance among prepared DCL structured GDEs, which also shows a significantly higher performance than the conventional single CL structured GDEs due to the novel structure of DCL. Finally, a good durability of 2/4-DCL GDE indicates the feasibility in practical HT-PEMFC.

Research paper thumbnail of Control strategy of a fuel-cell power module for electric forklift

International Journal of Hydrogen Energy, 2021

h i g h l i g h t s Lift truck simulation model with hybrid power pack is developed. PEMFC-Batter... more h i g h l i g h t s Lift truck simulation model with hybrid power pack is developed. PEMFC-Battery hybrid model for lift truck application was analyzed. Real lift truck load cycle was simulated.

Research paper thumbnail of HYDRIDE4MOBILITY: An EU HORIZON 2020 project on hydrogen powered fuel cell utility vehicles using metal hydrides in hydrogen storage and refuelling systems

International Journal of Hydrogen Energy, 2021

h i g h l i g h t s Advanced metal hydrides for H storage and compression were proposed. MH conta... more h i g h l i g h t s Advanced metal hydrides for H storage and compression were proposed. MH containers with improved H charge-discharge dynamic performance. Integrated with PEM fuel cell hydrogen energy system was developed. EU Horizon 2020 RISE project 778307 project HYDRIDE4MOBILITY. Hydrogen powered forklift uses MH based H storage and PEM fuel cell.

Research paper thumbnail of A Comprehensive Thermoelectric Cooler (TEC) Modelling

SSRN Electronic Journal, 2020

Faced with the ongoing energy and electricity crises in South Africa and by extension Africa, thi... more Faced with the ongoing energy and electricity crises in South Africa and by extension Africa, this paper presents a comprehensive model of Thermo-Electric Cooler (TEC), in a bid to devise an innovative renewable energy cooler to serve as an efficient heat pump, in which a low DC power source can be applied to it to generate cold, thereby decreasing the total power consumption. The novelty brought forward is an original simulated TEC model in MatLab / Simulink that can easily be configured with respect to a given DC source and thermal load, to determine a TEC optimal operational parameters to increase its heat absorption (cooling power Qc) capacity and as well its coefficient of performance (CoP).

Research paper thumbnail of Effect of Accelerated Stress Testing on High Temperature Proton Exchange Membrane Fuel Cell

ECS Meeting Abstracts, 2017

The durability of high temperature proton exchange membrane (HT-PEM) fuel cells is very important... more The durability of high temperature proton exchange membrane (HT-PEM) fuel cells is very important for its long term performance and commercialization. Commercialization demands progress, especially in the development of fuel cell catalyst materials and carbon supports. The role of platinum and carbon in the catalytic layer are crucial for the stable performance of a fuel cell. Potential cycling is used to evaluate the stability of platinum and carbon support material of catalyst layer. Fuel cells operated under cycling conditions have lower durability than those operated under steady state conditions. The aim of this work is to study degradation of phosphoric acid doped polybenzimidazole membrane based fuel cell under accelerated potential cycling conditions. Potential cycling degrades fuel cell performance. Understanding this degradation related issues associated with potential cycling is necessary to improve the durability of HT-PEM fuel cell. The fuel cell is cycled between open ...

Research paper thumbnail of Facile Preparation of a Surface-Enriched Pt Layer Over Pd/C as an Efficient Oxygen Reduction Catalyst With Enhanced Activity and Stability

Journal of Electrochemical Energy Conversion and Storage, 2020

Pt-enriched surface layer formation on Vulcan carbon-supported Pd (Pt@Pd/C) was successfully prep... more Pt-enriched surface layer formation on Vulcan carbon-supported Pd (Pt@Pd/C) was successfully prepared through a simple and one-pot formic acid reduction approach without any stabilizing agent. The electrocatalytic performance of Pt@Pd/C catalyst toward an oxygen reduction reaction (ORR) in alkaline medium was studied and also compared with standard carbon-supported Pt (Pt/C) and Pd (Pd/C) catalysts. The Pt@Pd/C exhibits higher electrochemical active surface area (74.7 m2/g) and mass activity (1.38 mA/µg) than Pt/C, Pd/C, and contending with standard reported catalysts. In durability tests, Pt@Pd/C showed negligible loss of intrinsic activity (∼10%) after 10,000 cycles which confirmed improved stability than Pt-based catalysts for ORR in KOH medium. This improved electrocatalytic performance could be attributed to their structural characteristics of the Pt-enriched surface layer on Pd/C-core and the compressive lattice strain on Pt. The present investigation demonstrates the simple p...

Research paper thumbnail of PEMFC for aeronautic applications: A review on the durability aspects

Open Engineering, 2017

Proton exchange membrane fuel cells (PEMFC) not only offer more efficient electrical energy conve... more Proton exchange membrane fuel cells (PEMFC) not only offer more efficient electrical energy conversion, relative to on-ground/backup turbines but generate by-products useful in aircraft such as heat for ice prevention, deoxygenated air for fire retardation and drinkable water for use on-board. Consequently, several projects (e.g. DLR-H2 Antares and RAPID2000) have successfully tested PEMFC-powered auxiliary unit (APU) for manned/unmanned aircraft. Despite the progress from flying PEMFC-powered small aircraft with 20 kW power output as high as 1 000 m at 100 km/h to 33 kW at 2 558 m, 176 km/h [1, 2, 3], durability and reliability remain key challenges. This review reports on the inadequate understanding of behaviour of PEMFC under aeronautic conditions and the lack of predictive methods conducive for aircraft that provide real-time information on the State of Health of PEMFCs.Highlights: The main research findings are–To minimize performance loss due to high altitude and inclination ...

Research paper thumbnail of Ex-Situ Electrochemical Characterization of IrO2 Synthesized by a Modified Adams Fusion Method for the Oxygen Evolution Reaction

Catalysts, 2019

The development of highly stable and active electrocatalysts for the oxygen evolution reaction (O... more The development of highly stable and active electrocatalysts for the oxygen evolution reaction (OER) has attracted significant research interest. IrO2 is known to show good stability during the OER however it is not known to be the most active. Thus, significant research has been dedicated to enhance the activity of IrO2 toward the OER. In this study, IrO2 catalysts were synthesized using a modified Adams fusion method. The Adams fusion method is simple and is shown to directly produce nano-sized metal oxides. The effect of the Ir precursor salt to the NaNO3 ratio and the fusion temperature on the OER activity of the synthesized IrO2 electrocatalysts, was investigated. The OER activity and durability of the IrO2 electrocatalysts were evaluated ex-situ via cyclic voltammetry (CV), chronopotentiometry (CP), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). Physical properties of the IrO2 electrocatalysts were evaluated via X-ray diffraction (XRD), transm...

Research paper thumbnail of Dual-shelled Cu2O@Cu9S5@MnO2 hollow spheres as advanced cathode material for energy storage

Journal of Alloys and Compounds, 2019

‡ Miaomiao Cao and Hui Wang contributed equally. Abstract： ： ： ：In this study, dual-shelled Cu 2 ... more ‡ Miaomiao Cao and Hui Wang contributed equally. Abstract： ： ： ：In this study, dual-shelled Cu 2 O@Cu 9 S 5 @MnO 2 hollow spheres with high surface area and porosity are developed as cathode material for electrochemical energy storage. Initially, Cu 2 O spheres are prepared via a hydrothermal method, which act as templates for subsequent procedure of forming hollow spheres with core(Cu 2 O)-shell(Cu 9 S 5) structure. Subsequently, porous MnO 2 shells is deposited on Cu 2 O@Cu 9 S 5 hollow spheres to form dual-shelled hollow spheres. In alkaline

Research paper thumbnail of Hydrogen refuelling station with integrated metal hydride compressor: Layout features and experience of three-year operation

International Journal of Hydrogen Energy, 2019

Research paper thumbnail of Achieving high Pt utilization and superior performance of high temperature polymer electrolyte membrane fuel cell by employing low-Pt-content catalyst and microporous layer free electrode design

Journal of Power Sources, 2019

• GDEs with low Pt loadings are developed for HT-PEMFC. • Combining low-Pt-content catalyst and M... more • GDEs with low Pt loadings are developed for HT-PEMFC. • Combining low-Pt-content catalyst and MPL-free structure is a way to reduce Pt use. • The Pt loading can be lowered to 0.2 mg cm −2 and still with satisfactory performance. • Ultra-low Pt loading can be expected from this strategy by enhancing CL quality.

Research paper thumbnail of Development of a Portable Polymer Electrolyte Membrane Fuel Cell System Using Metal Hydride as the Hydrogen Storage Medium

ECS Transactions, 2016

This paper describes the development of a Portable Polymer Electrolyte Membrane Fuel Cell / PEMFC... more This paper describes the development of a Portable Polymer Electrolyte Membrane Fuel Cell / PEMFC system that was developed at HySA Systems Competence Centre. The system has a rated peak output power of 130W at 240Vac and 5Vdc USB output power. Hydrogen is supplied from Metal Hydride (MH) hydrogen storage canister which uses multi-component AB2 – type hydrogen storage hydride alloy. The in-house developed MH canister was made up of stainless steel tube with external aluminium fins and had a maximum hydrogen storage capacity of 90 NLH2. The improvement of H2 discharge dynamic performance of the MH bed, which is cooled down in the course of H2 desorption, was achieved by the placement of the MH canister in front of exhaust of air cooling system of the PEMFC stack. By the utilisation of the PEMFC waste heat, in combination with the external fins (increase of heat exchange area) and compacting the MH material with Thermal Expanded Graphite / TEG (improvement of the effective thermal con...

Research paper thumbnail of Oxygen reduction reaction on Pt-Pd catalysts supported on carbon xerogels: Effect of the synthesis method

International Journal of Hydrogen Energy, 2018

In this work, Pt-Pd nanoparticles supported on carbon xerogels (Pt-Pd/CX) were synthesised employ... more In this work, Pt-Pd nanoparticles supported on carbon xerogels (Pt-Pd/CX) were synthesised employing unusual routes, in order to evaluate its activity toward the oxygen reduction reaction (ORR). The synthesis methods produced materials with the planned composition (metal content close to 40 wt % and Pt:Pd atomic ratios around 1:2), with Pt, Pd and alloyed Pt-Pd nanoparticles well dispersed on the carbon support. The content of Pt in the nanoparticles was optimised through these procedures, placing this metal at the surface. As a consequence, the Pt-Pd/CX catalysts displayed high activity toward the ORR and remarkable resistance to corrosion, overcoming the electrocatalytic properties of a commercial Pt/C catalyst. Moreover, these catalysts involve four electrons in the ORR. Therefore, the study here presented indicated that the as-synthesised Pt-Pd/CX catalysts are suitable candidates to be employed as cathodes in proton exchange membrane fuel cells.

Research paper thumbnail of A concept of combined cooling, heating and power system utilising solar power and based on reversible solid oxide fuel cell and metal hydrides

International Journal of Hydrogen Energy, 2018

In energy systems, multi-generation including co-generation and tri-generation has gained tremend... more In energy systems, multi-generation including co-generation and tri-generation has gained tremendous interest in the recent years as an effective way of waste heat recovery. Solid oxide fuel cells are efficient power plants that not only generate electricity with high energy efficiency but also produce high quality waste heat that can be further used for hot and chilled water production. In this work, we present a concept of combined cooling, heating and power (CCHP) energy system which uses solar power as a primary energy source and utilizes a reversible solid oxide fuel cell (R-SOFC) for producing hydrogen and generating electricity in the electrolyser (SOEC) and fuel cell (SOFC) modes, respectively. The system uses "high temperature" metal hydride (MH) for storage of both hydrogen and heat, as well as "low temperature" MH's for the additional heat management, including hot water supply, residential heating during winter time, or cooling/air conditioning during summer time. The work presents evaluation of energy balances of the system components, as well as heat-and-mass transfer modelling of MH beds in metal hydride hydrogen and heat storage system (MHHS; MgH 2), MH hydrogen compressor (MHHC; AB 5 ; A ¼ La þ Mm, B] Ni þ Co þ Al þ Mn) and MH heat pump (MHHP; AB 2 ; A ¼ Ti þ Zr, B]Mn þ Cr þ Ni þ Fe). A case study of a 3 kWe R-SOFC is analysed and discussed. The results showed that the energy efficiencies are 69.4 and 72.4% in electrolyser and fuel cell modes, respectively. The round-trip COP's of metal hydride heat management system (MHHC þ MHHP) are close to 40% for both heating and cooling outputs. Moreover, the tri-generation leads to an improvement of 36% in round-trip energy efficiency as compared to that of a stand-alone R-SOFC.

Research paper thumbnail of Eliminating micro-porous layer from gas diffusion electrode for use in high temperature polymer electrolyte membrane fuel cell

Journal of Power Sources, 2017

In this work, we report a simple strategy to improve the performance of high temperature polymer ... more In this work, we report a simple strategy to improve the performance of high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) by eliminating the micro-porous layer (MPL) from its gas diffusion electrodes (GDEs). Due to the absence of liquid water and the general use of high amount of catalyst, the MPL in a HT-PEMFC system works limitedly. Contrarily, the elimination of the MPL leads to an interlaced micropore/macropore composited structure in the catalyst layer (CL), which favors gas transport and catalyst utilization, resulting in a greatly improved single cell performance. At the normal working voltage (0.6 V), the current density of the GDE eliminated MPL reaches 0.29 A cm −2 , and a maximum power density of 0.54 W cm −2 at 0.36 V is obtained, which are comparable to the best results yet reported for the HT-PEMFCs with similar Pt loading and operated using air. Furthermore, the MPL-free GDE maintains an excellent durability during a preliminary 1,400 hour HT-PEMFC operation, owing to its structure advantages, indicating the feasibility of this electrode for practical applications.

Research paper thumbnail of Enhanced Intrinsic Activity and Stability of Au–Rh Bimetallic Nanostructures as a Supportless Cathode Electrocatalyst for Oxygen Reduction in Alkaline Fuel Cells

ACS Sustainable Chemistry & Engineering, 2016

The electroreduction of dioxygen on supportless Au-Rh bimetallic nanostructures (Au-Rh 33 NC) syn... more The electroreduction of dioxygen on supportless Au-Rh bimetallic nanostructures (Au-Rh 33 NC) synthesized by a surfactant template-free, single step chemical reduction method occurred 34 with high intrinsic activity in an alkaline medium. Cyclic voltammetry and linear scan 35 voltammetry together with X-ray diffraction and high-resolution electron microscopy showed that the improved performance of the Au-Rh NC towards dioxygen reduction could be due to the 37 synergistic electronic effects of nano-bimetallic combination and its cluster-like morphology. 38 The electrochemically active surface area (ECSA) was estimated to be 37.2 m 2 g-1 for 39 supportless Au-Rh NC with a 3:1 atomic composition, which was higher than that reported for 40 Ag-based nanocatalysts. The intrinsic activities (IA) of the supportless and carbon supported Au-41 Rh (3:1) NCs were 3.25 and 3.0 mA/cm 2 , respectively, which were higher than those of the 42 standard Pt/C (0.1 mA/cm 2) 45 Au/C catalysts for the oxygen reduction reaction (ORR). Oxygen 43 reduction on both catalysts followed a direct four electron pathway. The accelerated durability 44 test carried out by continuous potential cycling showed that the 3:1 ratio of Au-Rh 45 nanostructures had excellent stability with a 20% increase in ECSA after 10000 potential cycles, 46 highlighting their potential application for real systems.

Research paper thumbnail of Pt3M (M: Co, Ni and Fe) Bimetallic Alloy Nanoclusters as Support-Free Electrocatalysts with Improved Activity and Durability for Dioxygen Reduction in PEM Fuel Cells

Electrocatalysis, 2016

Pt 3 M (M: Co, Ni and Fe) bimetallic alloy nanoclusters were synthesized by a novel and simple ch... more Pt 3 M (M: Co, Ni and Fe) bimetallic alloy nanoclusters were synthesized by a novel and simple chemical reduction approach, and employed as the promising electrocatalyst to accelerate the kinetics of oxygen reduction reaction (ORR) for polymer electrolyte membrane fuel cells. From XRD, the positive shift of diffraction angle confirms the alloy formation between Pt and M and the elemental composition was confirmed by energy dispersive X-ray spectroscopy analysis. The nanocluster morphology and particle size was determined using scanning and transmission electron microscopy analysis. The ORR kinetic parameters for Pt-M electrocatalysts were calculated and compared with reported Pt/C catalysts. Among the Pt-M electrocatalysts, Pt-Co was found to be the most efficient catalyst having the higher mass and specific activity (at 0.9 V vs. RHE) of 0.44 mA/μg and 0.69 mA/cm 2 , respectively. The accelerated durability test reveals that the Pt-M bimetallic alloy nanoclusters retain appreciable surface area and mass activity after 8000 potential cycles confirms good long-term durability, and also competing with the reported benchmark ORR catalysts.