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Papers by lingchao xia

Research paper thumbnail of A Hybrid Redox‐Mediated Zinc‐Air Fuel Cell for Scalable and Sustained Power Generation

Angewandte Chemie, Feb 23, 2024

Research paper thumbnail of Temperature Gradient Analyses of a Tubular Solid Oxide Fuel Cell Fueled by Methanol

Transactions of Tianjin University, Aug 10, 2022

Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electr... more Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electrochemical reactions and convective flows within the cells. Therefore, a 2D mathematical model is established herein to investigate the thermal responses of a tubular methanol-fueled SOFC. Results show that unlike the low-temperature condition of 873 K, where the peak temperature gradient occurs at the cell center, it appears near the fuel inlet at 1073 K because of the rapid temperature rise induced by the elevated current density. Despite the large heat convection capacity, excessive air could not effectively eliminate the harmful temperature gradient caused by the large current density. Thus, optimal control of the current density by properly selecting the operating potential could generate a local thermal neutral state. Interestingly, the maximum axial temperature gradient could be reduced by about 18% at 973 K and 20% at 1073 K when the air with a 5 K higher temperature is supplied. Additionally, despite the higher electrochemical performance observed, the cell with a counter-flow arrangement featured by a larger hot area and higher maximum temperature gradients is not preferable for a ceramic SOFC system considering thermal durability. Overall, this study could provide insightful thermal information for the operating condition selection, structure design, and stability assessment of realistic SOFCs combined with their internal reforming process.

Research paper thumbnail of Effects of cathode thickness and microstructural properties on the performance of protonic ceramic fuel cell (PCFC): A 3D modelling study

International Journal of Hydrogen Energy, 2022

Research paper thumbnail of Numerical study of high temperature proton exchange membrane fuel cell (HT-PEMFC) with a focus on rib design

International Journal of Hydrogen Energy, Jun 1, 2021

Abstract The rib size is a critical engineering design parameter for high temperature proton exch... more Abstract The rib size is a critical engineering design parameter for high temperature proton exchange membrane fuel cell (HT-PEMFC) stack development, yet it hasn't been studied for HT-PEMFC. A three-dimensional, non-isothermal model was developed in this work to investigate the effect of channel to rib width ratios (CRWR) on the performance of HT-PEMFC. The reaction heat caused by entropy change was divided into cathodic half-reaction heat and anodic half-reaction heat. The results show that the ratio value significantly influence the gas diffusion, electron conduction and the distribution of current density in the porous electrodes. Increasing this ratio facilitates gas transport in the porous electrode but causes higher ohmic loss due to longer distance for electron conduction. As a result, an optimal ratio of about 1 is observed, which results in a peak power density of 0.428 W/cm2. High current density is observed under the channel with a small ratio value while a high ratio value would cause high current density to appear under the rib, signifying the rib size effect on electrochemical behavior of HT-PEMFC. Apart from the electrical power output, the CRWR value also greatly influences the fluid flow and temperature distribution inside the cell, which would influence the long-term stability of HT-PEMFC. In the subsequent studies, efforts will be made to develop new stack configurations with more uniform gas distribution, short electron conduction path and low temperature gradient.

Research paper thumbnail of Modelling of an integrated protonic ceramic electrolyzer cell (PCEC) for methanol synthesis

Journal of Power Sources, Mar 1, 2023

Research paper thumbnail of Thermo-electrochemical modelling of high temperature methanol-fuelled solid oxide fuel cells

Applied Energy, Jun 1, 2021

Abstract Methanol is a promising fuel for the solid oxide fuel cell (SOFC) due to its easy storag... more Abstract Methanol is a promising fuel for the solid oxide fuel cell (SOFC) due to its easy storage and transportation compared with hydrogen. As no thermo-electrochemical modelling study has been conducted on methanol-fuelled SOFC, a 2D model is developed to simulate the methanol decomposition reaction, water gas shift reaction, electrochemical reactions, heat and mass transfer processes in the methanol-fuelled SOFC. After model validation, parametric simulations are performed to investigate the effects of the operating potential, steam to carbon ratio, the inlet temperature and fuel/air flow rates on the performance of SOFCs. At 1073 K, the peak power density of methanol-fuelled SOFC is higher than 10000 W m−2 with the steam to carbon ratio of 1. In addition, the temperature distribution in SOFC could be remarkably affected by the working conditions due to the chemical/electrochemical reactions and overpotential losses. Large temperature variation (nearly 180 K) between the inlet and outlet of the SOFC is observed mainly due to greatly improved current density at low operating potential. Also, temperature reduction can be achieved by increasing the steam to carbon ratio and gas flow rates (higher than 170 SCCM for air and 0.1 ml min−1 for fuel mixture, respectively), which could improve the long-term stability from the perspective of the thermal stress but inevitably lower the efficiency of the SOFC. Meanwhile, higher inlet temperature not only enhances the power output, but improves the uniformity of the cell temperature distribution. Overall, the investigations of the present study could serve as a solid guidance to understand the thermal characteristics of solid oxide fuel cells running on mixture of the steam and methanol.

Research paper thumbnail of A comprehensive review of solid oxide fuel cells operating on various promising alternative fuels

Energy Conversion and Management, Feb 1, 2022

Research paper thumbnail of Numerical study of vapor behavior in high temperature PEM fuel cell under key material and operating parameters

International Journal of Green Energy, Aug 30, 2021

ABSTRACT The water issue of high-temperature proton exchange membrane fuel cell (HT-PEMFC) is rar... more ABSTRACT The water issue of high-temperature proton exchange membrane fuel cell (HT-PEMFC) is rarely studied in the previous work. However, the different water vapor behaviors might greatly influence both cell performance and stability. In order to gain a fundamental understanding of the vapor behaviors in HT-PEMFC, a 3D computational fluid dynamics model and a 2D transient model were developed to investigate the effects of materials properties and operating parameters on the vapor behavior. Temperature, membrane materials, and phosphoric acid doping degrees are examined. The results show that higher temperature and phosphoric acid doping degrees with PBI membrane would lead to a significant increase of water vapor generation at cathode. For the transient model, the dynamics of vapor accumulation were observed with the dead-end anode. It is revealed that vapor transport and distribution get adapted to a dynamic equilibrium after 18 sec. According to these results, a periodic purging at anode with optimized purging time is still needed to remove the accumulated water vapor. The findings of this paper can be further applied in the design of fuel cell controller.

Research paper thumbnail of A comprehensive modelling study of all vanadium redox flow battery: Revealing the combined effects of electrode structure and surface property

Journal of energy storage, Aug 1, 2023

Research paper thumbnail of A comprehensive modelling study of all vanadium redox flow battery: Revealing the combined effects of electrode structure and surface property

Journal of Energy Storage

Research paper thumbnail of Modelling of an integrated protonic ceramic electrolyzer cell (PCEC) for methanol synthesis

Research paper thumbnail of Reconstruction and optimization of catalyst layer of high temperature proton exchange membrane fuel cell

International Journal of Hydrogen Energy

Research paper thumbnail of Temperature Gradient Analyses of a Tubular Solid Oxide Fuel Cell Fueled by Methanol

Transactions of Tianjin University

Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electr... more Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electrochemical reactions and convective flows within the cells. Therefore, a 2D mathematical model is established herein to investigate the thermal responses of a tubular methanol-fueled SOFC. Results show that unlike the low-temperature condition of 873 K, where the peak temperature gradient occurs at the cell center, it appears near the fuel inlet at 1073 K because of the rapid temperature rise induced by the elevated current density. Despite the large heat convection capacity, excessive air could not effectively eliminate the harmful temperature gradient caused by the large current density. Thus, optimal control of the current density by properly selecting the operating potential could generate a local thermal neutral state. Interestingly, the maximum axial temperature gradient could be reduced by about 18% at 973 K and 20% at 1073 K when the air with a 5 K higher temperature is supplied. ...

Research paper thumbnail of Optimization of gas diffusion layer in high temperature PEMFC with the focuses on thickness and porosity

Applied Energy, 2021

Abstract Wide ranges of thickness (e.g. 100–400 μm) and porosity (e.g. 30–70%) of gas diffusion l... more Abstract Wide ranges of thickness (e.g. 100–400 μm) and porosity (e.g. 30–70%) of gas diffusion layer (GDL) in a high temperature proton exchange membrane fuel cell (HT-PEMFC) are available in the literature. However, the effects of GDL porosity and thickness on electron conduction and gas distribution uniformity (under the rib and under the channel) are unclear. In this study, a numerical non-isothermal 3D model was developed. After model validation, parametric analyses were performed to investigate the effects of thickness and porosity on flow uniformity (under the rib and under the channel), diffusion flux and ohmic resistance. It is found that both the flow uniformity and ohmic resistance increase with increasing thickness and porosity. However, the thickness and porosity have opposite influence on diffusion flux, which decreases with increasing GDL thickness but increases with increasing porosity. Unlike the previous research suggesting thin GDL with high porosity, optimal GDL thickness and porosity are found in the present study. The appropriate GDL thicknesses for anode and cathode are 80–120 μm and 140–170 μm respectively while the optimal value for GDL porosity is 35–45%. This study clearly demonstrates that we can further achieve a performance increment of 7.7% by carefully controlling the thickness and porosity of GDL.

Research paper thumbnail of A comprehensive review of solid oxide fuel cells operating on various promising alternative fuels

Energy Conversion and Management, 2022

Research paper thumbnail of Effects of cathode thickness and microstructural properties on the performance of protonic ceramic fuel cell (PCFC): A 3D modelling study

International Journal of Hydrogen Energy, 2021

Research paper thumbnail of Optimization of catalyst layer thickness for achieving high performance and low cost of high temperature proton exchange membrane fuel cell

Applied Energy, 2021

Abstract The thickness of catalyst layer (CL) determines the electrochemical performance and the ... more Abstract The thickness of catalyst layer (CL) determines the electrochemical performance and the cost of high temperature proton exchange membrane fuel cell (HT-PEMFC). However, various values (e.g. 100 μm, 50 μm, 10 μm) of CL thickness are reported in the previous studies. To identify the optimal CL thickness to reduce the PEMFC cost without sacrificing the electrochemical performance, it is necessary to first identify the effective reaction thickness (ERT) of both anode and cathode. A numerical non-isothermal 3D model was developed considering the activation loss, concentration loss and ohmic loss at two electrodes, respectively. After model validation, parametric analyses were performed to investigate the effects of temperature, working voltage and flow rate on the performance of the fuel cell, especially on ERT. It is found that the ERT increases with increasing temperature. The working voltage and the cathode flow rate have opposite influences on the ERT of the two electrodes. The ERT highly depends on the ratio of activation loss and concentration loss (ηact+ηconc) to ohmic loss ηohmic. Considering the utilization rate of the catalyst and cell performance, the appropriate CL thicknesses for anode and cathode electrode are 10–17 μm and 15–30 μm, respectively. This study clearly demonstrates that we can reduce the CL cost and maintain high fuel cell performance by carefully controlling the thickness of CL.

Research paper thumbnail of Numerical study of high temperature proton exchange membrane fuel cell (HT-PEMFC) with a focus on rib design

International Journal of Hydrogen Energy, 2021

Abstract The rib size is a critical engineering design parameter for high temperature proton exch... more Abstract The rib size is a critical engineering design parameter for high temperature proton exchange membrane fuel cell (HT-PEMFC) stack development, yet it hasn't been studied for HT-PEMFC. A three-dimensional, non-isothermal model was developed in this work to investigate the effect of channel to rib width ratios (CRWR) on the performance of HT-PEMFC. The reaction heat caused by entropy change was divided into cathodic half-reaction heat and anodic half-reaction heat. The results show that the ratio value significantly influence the gas diffusion, electron conduction and the distribution of current density in the porous electrodes. Increasing this ratio facilitates gas transport in the porous electrode but causes higher ohmic loss due to longer distance for electron conduction. As a result, an optimal ratio of about 1 is observed, which results in a peak power density of 0.428 W/cm2. High current density is observed under the channel with a small ratio value while a high ratio value would cause high current density to appear under the rib, signifying the rib size effect on electrochemical behavior of HT-PEMFC. Apart from the electrical power output, the CRWR value also greatly influences the fluid flow and temperature distribution inside the cell, which would influence the long-term stability of HT-PEMFC. In the subsequent studies, efforts will be made to develop new stack configurations with more uniform gas distribution, short electron conduction path and low temperature gradient.

Research paper thumbnail of Multi‐Functional Hydrogels for Flexible Zinc‐Based Batteries Working under Extreme Conditions (Adv. Energy Mater. 34/2021)

Advanced Energy Materials, 2021

Zinc‐based batteries are potential candidates for flexible energy storage due to their high capac... more Zinc‐based batteries are potential candidates for flexible energy storage due to their high capacity, low cost, and intrinsic safety. Hydrogel electrolytes with saturated aqueous solvents can provide remarkable electrochemical performance while retaining satisfactory flexibility for zinc‐based batteries. The past decades have witnessed their fast growth. However, the study of zinc‐based batteries with hydrogel electrolytes under extreme conditions is still in the early stages and many technical issues remain to be addressed. In this review, the physical and chemical properties of hydrogel electrolytes are discussed for application in zinc‐based batteries. Strategies towards hydrogel electrolytes and flexible zinc‐based batteries under extremely high/low temperatures or under deformation conditions and their behaviors are reviewed and analyzed. Moreover, design strategies for all‐around hydrogel electrolyte that are appropriate for use in all these extreme conditions are proposed. A perspective discussing the challenges and future directions of hydrogel electrolyte for zinc‐based batteries is also provided.

Research paper thumbnail of Numerical study of triple‐phase boundary length in high‐temperature proton exchange membrane fuel cell

International Journal of Energy Research, 2021

Catalyst layer (CL) is the most important component in the high‐temperature proton exchange membr... more Catalyst layer (CL) is the most important component in the high‐temperature proton exchange membrane fuel cell (HT‐PEMFC), as it offers reaction sites for hydrogen oxidation reaction (HOR) and oxygen reduction reactions (ORR). As the electrochemical reactions take place at gas/electron/proton interface, the length of this triple‐phase boundary (TPB) in the CL governs the rate of electrochemical reactions. As the TPB in the HT‐PEMFC has not been studied yet, a numerical non‐isothermal 3D model and a percolation micro model were developed in this work to investigate the effect of CLs' properties on both the TPB length and cell performance. The volume fractions, particle size, and particle size ratio of ionomer and Pt/C were selected for optimization. The results show that peak current density could be achieved at an ionomer volume fraction of 52%. Further improvement of cell performance requires smaller particle size and smaller particle size ratio of ionomer.

Research paper thumbnail of A Hybrid Redox‐Mediated Zinc‐Air Fuel Cell for Scalable and Sustained Power Generation

Angewandte Chemie, Feb 23, 2024

Research paper thumbnail of Temperature Gradient Analyses of a Tubular Solid Oxide Fuel Cell Fueled by Methanol

Transactions of Tianjin University, Aug 10, 2022

Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electr... more Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electrochemical reactions and convective flows within the cells. Therefore, a 2D mathematical model is established herein to investigate the thermal responses of a tubular methanol-fueled SOFC. Results show that unlike the low-temperature condition of 873 K, where the peak temperature gradient occurs at the cell center, it appears near the fuel inlet at 1073 K because of the rapid temperature rise induced by the elevated current density. Despite the large heat convection capacity, excessive air could not effectively eliminate the harmful temperature gradient caused by the large current density. Thus, optimal control of the current density by properly selecting the operating potential could generate a local thermal neutral state. Interestingly, the maximum axial temperature gradient could be reduced by about 18% at 973 K and 20% at 1073 K when the air with a 5 K higher temperature is supplied. Additionally, despite the higher electrochemical performance observed, the cell with a counter-flow arrangement featured by a larger hot area and higher maximum temperature gradients is not preferable for a ceramic SOFC system considering thermal durability. Overall, this study could provide insightful thermal information for the operating condition selection, structure design, and stability assessment of realistic SOFCs combined with their internal reforming process.

Research paper thumbnail of Effects of cathode thickness and microstructural properties on the performance of protonic ceramic fuel cell (PCFC): A 3D modelling study

International Journal of Hydrogen Energy, 2022

Research paper thumbnail of Numerical study of high temperature proton exchange membrane fuel cell (HT-PEMFC) with a focus on rib design

International Journal of Hydrogen Energy, Jun 1, 2021

Abstract The rib size is a critical engineering design parameter for high temperature proton exch... more Abstract The rib size is a critical engineering design parameter for high temperature proton exchange membrane fuel cell (HT-PEMFC) stack development, yet it hasn't been studied for HT-PEMFC. A three-dimensional, non-isothermal model was developed in this work to investigate the effect of channel to rib width ratios (CRWR) on the performance of HT-PEMFC. The reaction heat caused by entropy change was divided into cathodic half-reaction heat and anodic half-reaction heat. The results show that the ratio value significantly influence the gas diffusion, electron conduction and the distribution of current density in the porous electrodes. Increasing this ratio facilitates gas transport in the porous electrode but causes higher ohmic loss due to longer distance for electron conduction. As a result, an optimal ratio of about 1 is observed, which results in a peak power density of 0.428 W/cm2. High current density is observed under the channel with a small ratio value while a high ratio value would cause high current density to appear under the rib, signifying the rib size effect on electrochemical behavior of HT-PEMFC. Apart from the electrical power output, the CRWR value also greatly influences the fluid flow and temperature distribution inside the cell, which would influence the long-term stability of HT-PEMFC. In the subsequent studies, efforts will be made to develop new stack configurations with more uniform gas distribution, short electron conduction path and low temperature gradient.

Research paper thumbnail of Modelling of an integrated protonic ceramic electrolyzer cell (PCEC) for methanol synthesis

Journal of Power Sources, Mar 1, 2023

Research paper thumbnail of Thermo-electrochemical modelling of high temperature methanol-fuelled solid oxide fuel cells

Applied Energy, Jun 1, 2021

Abstract Methanol is a promising fuel for the solid oxide fuel cell (SOFC) due to its easy storag... more Abstract Methanol is a promising fuel for the solid oxide fuel cell (SOFC) due to its easy storage and transportation compared with hydrogen. As no thermo-electrochemical modelling study has been conducted on methanol-fuelled SOFC, a 2D model is developed to simulate the methanol decomposition reaction, water gas shift reaction, electrochemical reactions, heat and mass transfer processes in the methanol-fuelled SOFC. After model validation, parametric simulations are performed to investigate the effects of the operating potential, steam to carbon ratio, the inlet temperature and fuel/air flow rates on the performance of SOFCs. At 1073 K, the peak power density of methanol-fuelled SOFC is higher than 10000 W m−2 with the steam to carbon ratio of 1. In addition, the temperature distribution in SOFC could be remarkably affected by the working conditions due to the chemical/electrochemical reactions and overpotential losses. Large temperature variation (nearly 180 K) between the inlet and outlet of the SOFC is observed mainly due to greatly improved current density at low operating potential. Also, temperature reduction can be achieved by increasing the steam to carbon ratio and gas flow rates (higher than 170 SCCM for air and 0.1 ml min−1 for fuel mixture, respectively), which could improve the long-term stability from the perspective of the thermal stress but inevitably lower the efficiency of the SOFC. Meanwhile, higher inlet temperature not only enhances the power output, but improves the uniformity of the cell temperature distribution. Overall, the investigations of the present study could serve as a solid guidance to understand the thermal characteristics of solid oxide fuel cells running on mixture of the steam and methanol.

Research paper thumbnail of A comprehensive review of solid oxide fuel cells operating on various promising alternative fuels

Energy Conversion and Management, Feb 1, 2022

Research paper thumbnail of Numerical study of vapor behavior in high temperature PEM fuel cell under key material and operating parameters

International Journal of Green Energy, Aug 30, 2021

ABSTRACT The water issue of high-temperature proton exchange membrane fuel cell (HT-PEMFC) is rar... more ABSTRACT The water issue of high-temperature proton exchange membrane fuel cell (HT-PEMFC) is rarely studied in the previous work. However, the different water vapor behaviors might greatly influence both cell performance and stability. In order to gain a fundamental understanding of the vapor behaviors in HT-PEMFC, a 3D computational fluid dynamics model and a 2D transient model were developed to investigate the effects of materials properties and operating parameters on the vapor behavior. Temperature, membrane materials, and phosphoric acid doping degrees are examined. The results show that higher temperature and phosphoric acid doping degrees with PBI membrane would lead to a significant increase of water vapor generation at cathode. For the transient model, the dynamics of vapor accumulation were observed with the dead-end anode. It is revealed that vapor transport and distribution get adapted to a dynamic equilibrium after 18 sec. According to these results, a periodic purging at anode with optimized purging time is still needed to remove the accumulated water vapor. The findings of this paper can be further applied in the design of fuel cell controller.

Research paper thumbnail of A comprehensive modelling study of all vanadium redox flow battery: Revealing the combined effects of electrode structure and surface property

Journal of energy storage, Aug 1, 2023

Research paper thumbnail of A comprehensive modelling study of all vanadium redox flow battery: Revealing the combined effects of electrode structure and surface property

Journal of Energy Storage

Research paper thumbnail of Modelling of an integrated protonic ceramic electrolyzer cell (PCEC) for methanol synthesis

Research paper thumbnail of Reconstruction and optimization of catalyst layer of high temperature proton exchange membrane fuel cell

International Journal of Hydrogen Energy

Research paper thumbnail of Temperature Gradient Analyses of a Tubular Solid Oxide Fuel Cell Fueled by Methanol

Transactions of Tianjin University

Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electr... more Thermal management in solid oxide fuel cells (SOFC) is a critical issue due to non-uniform electrochemical reactions and convective flows within the cells. Therefore, a 2D mathematical model is established herein to investigate the thermal responses of a tubular methanol-fueled SOFC. Results show that unlike the low-temperature condition of 873 K, where the peak temperature gradient occurs at the cell center, it appears near the fuel inlet at 1073 K because of the rapid temperature rise induced by the elevated current density. Despite the large heat convection capacity, excessive air could not effectively eliminate the harmful temperature gradient caused by the large current density. Thus, optimal control of the current density by properly selecting the operating potential could generate a local thermal neutral state. Interestingly, the maximum axial temperature gradient could be reduced by about 18% at 973 K and 20% at 1073 K when the air with a 5 K higher temperature is supplied. ...

Research paper thumbnail of Optimization of gas diffusion layer in high temperature PEMFC with the focuses on thickness and porosity

Applied Energy, 2021

Abstract Wide ranges of thickness (e.g. 100–400 μm) and porosity (e.g. 30–70%) of gas diffusion l... more Abstract Wide ranges of thickness (e.g. 100–400 μm) and porosity (e.g. 30–70%) of gas diffusion layer (GDL) in a high temperature proton exchange membrane fuel cell (HT-PEMFC) are available in the literature. However, the effects of GDL porosity and thickness on electron conduction and gas distribution uniformity (under the rib and under the channel) are unclear. In this study, a numerical non-isothermal 3D model was developed. After model validation, parametric analyses were performed to investigate the effects of thickness and porosity on flow uniformity (under the rib and under the channel), diffusion flux and ohmic resistance. It is found that both the flow uniformity and ohmic resistance increase with increasing thickness and porosity. However, the thickness and porosity have opposite influence on diffusion flux, which decreases with increasing GDL thickness but increases with increasing porosity. Unlike the previous research suggesting thin GDL with high porosity, optimal GDL thickness and porosity are found in the present study. The appropriate GDL thicknesses for anode and cathode are 80–120 μm and 140–170 μm respectively while the optimal value for GDL porosity is 35–45%. This study clearly demonstrates that we can further achieve a performance increment of 7.7% by carefully controlling the thickness and porosity of GDL.

Research paper thumbnail of A comprehensive review of solid oxide fuel cells operating on various promising alternative fuels

Energy Conversion and Management, 2022

Research paper thumbnail of Effects of cathode thickness and microstructural properties on the performance of protonic ceramic fuel cell (PCFC): A 3D modelling study

International Journal of Hydrogen Energy, 2021

Research paper thumbnail of Optimization of catalyst layer thickness for achieving high performance and low cost of high temperature proton exchange membrane fuel cell

Applied Energy, 2021

Abstract The thickness of catalyst layer (CL) determines the electrochemical performance and the ... more Abstract The thickness of catalyst layer (CL) determines the electrochemical performance and the cost of high temperature proton exchange membrane fuel cell (HT-PEMFC). However, various values (e.g. 100 μm, 50 μm, 10 μm) of CL thickness are reported in the previous studies. To identify the optimal CL thickness to reduce the PEMFC cost without sacrificing the electrochemical performance, it is necessary to first identify the effective reaction thickness (ERT) of both anode and cathode. A numerical non-isothermal 3D model was developed considering the activation loss, concentration loss and ohmic loss at two electrodes, respectively. After model validation, parametric analyses were performed to investigate the effects of temperature, working voltage and flow rate on the performance of the fuel cell, especially on ERT. It is found that the ERT increases with increasing temperature. The working voltage and the cathode flow rate have opposite influences on the ERT of the two electrodes. The ERT highly depends on the ratio of activation loss and concentration loss (ηact+ηconc) to ohmic loss ηohmic. Considering the utilization rate of the catalyst and cell performance, the appropriate CL thicknesses for anode and cathode electrode are 10–17 μm and 15–30 μm, respectively. This study clearly demonstrates that we can reduce the CL cost and maintain high fuel cell performance by carefully controlling the thickness of CL.

Research paper thumbnail of Numerical study of high temperature proton exchange membrane fuel cell (HT-PEMFC) with a focus on rib design

International Journal of Hydrogen Energy, 2021

Abstract The rib size is a critical engineering design parameter for high temperature proton exch... more Abstract The rib size is a critical engineering design parameter for high temperature proton exchange membrane fuel cell (HT-PEMFC) stack development, yet it hasn't been studied for HT-PEMFC. A three-dimensional, non-isothermal model was developed in this work to investigate the effect of channel to rib width ratios (CRWR) on the performance of HT-PEMFC. The reaction heat caused by entropy change was divided into cathodic half-reaction heat and anodic half-reaction heat. The results show that the ratio value significantly influence the gas diffusion, electron conduction and the distribution of current density in the porous electrodes. Increasing this ratio facilitates gas transport in the porous electrode but causes higher ohmic loss due to longer distance for electron conduction. As a result, an optimal ratio of about 1 is observed, which results in a peak power density of 0.428 W/cm2. High current density is observed under the channel with a small ratio value while a high ratio value would cause high current density to appear under the rib, signifying the rib size effect on electrochemical behavior of HT-PEMFC. Apart from the electrical power output, the CRWR value also greatly influences the fluid flow and temperature distribution inside the cell, which would influence the long-term stability of HT-PEMFC. In the subsequent studies, efforts will be made to develop new stack configurations with more uniform gas distribution, short electron conduction path and low temperature gradient.

Research paper thumbnail of Multi‐Functional Hydrogels for Flexible Zinc‐Based Batteries Working under Extreme Conditions (Adv. Energy Mater. 34/2021)

Advanced Energy Materials, 2021

Zinc‐based batteries are potential candidates for flexible energy storage due to their high capac... more Zinc‐based batteries are potential candidates for flexible energy storage due to their high capacity, low cost, and intrinsic safety. Hydrogel electrolytes with saturated aqueous solvents can provide remarkable electrochemical performance while retaining satisfactory flexibility for zinc‐based batteries. The past decades have witnessed their fast growth. However, the study of zinc‐based batteries with hydrogel electrolytes under extreme conditions is still in the early stages and many technical issues remain to be addressed. In this review, the physical and chemical properties of hydrogel electrolytes are discussed for application in zinc‐based batteries. Strategies towards hydrogel electrolytes and flexible zinc‐based batteries under extremely high/low temperatures or under deformation conditions and their behaviors are reviewed and analyzed. Moreover, design strategies for all‐around hydrogel electrolyte that are appropriate for use in all these extreme conditions are proposed. A perspective discussing the challenges and future directions of hydrogel electrolyte for zinc‐based batteries is also provided.

Research paper thumbnail of Numerical study of triple‐phase boundary length in high‐temperature proton exchange membrane fuel cell

International Journal of Energy Research, 2021

Catalyst layer (CL) is the most important component in the high‐temperature proton exchange membr... more Catalyst layer (CL) is the most important component in the high‐temperature proton exchange membrane fuel cell (HT‐PEMFC), as it offers reaction sites for hydrogen oxidation reaction (HOR) and oxygen reduction reactions (ORR). As the electrochemical reactions take place at gas/electron/proton interface, the length of this triple‐phase boundary (TPB) in the CL governs the rate of electrochemical reactions. As the TPB in the HT‐PEMFC has not been studied yet, a numerical non‐isothermal 3D model and a percolation micro model were developed in this work to investigate the effect of CLs' properties on both the TPB length and cell performance. The volume fractions, particle size, and particle size ratio of ionomer and Pt/C were selected for optimization. The results show that peak current density could be achieved at an ionomer volume fraction of 52%. Further improvement of cell performance requires smaller particle size and smaller particle size ratio of ionomer.