Shu Hearn Yu - Academia.edu (original) (raw)

Papers by Shu Hearn Yu

ACS Applied Energy Materials, 2019

Hybridized materials frequently exhibit boosting performances than the individual components in f... more Hybridized materials frequently exhibit boosting performances than the individual components in functional applications due to the intriguing synergistic effects. Nonetheless, the preparation of hybrid materials is often tedious, involving stepwise procedures with different synthesis approaches. To date, controlled synthesis of hybrid materials via a one-pot CVD process has rarely been explored. In this work, herein, we report successful synthesis of the MoS 2 /VS 2 hybrid by in-situ growing the MoS 2 microflowers on the VS 2 microflakes via a one-step CVD process for electrolytic hydrogen evolution reaction (HER) in an acid electrolyte. The MoS 2 /VS 2 hybrid exhibits enhanced HER performances than the standalone pristine MoS 2 and VS 2. Such improvement may be due to the formation of lightly vanadium-doped MoS 2 First-principle calculations further show that vanadium dopants can effectively enhance the inplane electrical conductivity and intrinsic activity of MoS 2 simultaneously. The proposed CVD strategy in this work is scalable, timesaving, and versatile, which can be used to grow a great variety of hybrid materials for different fields, enabling the cost-effective utilizations of recently reported novel materials.

ACS applied materials & interfaces, Jan 2, 2018

In this communication, we facily fabricated nanostructured CoP particles (150 to 200 nm) on carbo... more In this communication, we facily fabricated nanostructured CoP particles (150 to 200 nm) on carbon fiber paper (CFP) for hydrogen evolution reaction (HER) by a simple two-step process via a green route. In the first step, crystalline CoO nanocubes (150-200 nm) were loaded on CFP through a hydrothermal process at low temperature (120 °C). Interestingly, crystalline CoO nanocubes with a size 150-200 nm exhibited different growth mechanisms in contrast to the crystalline CoO nanocubes with a size <100 nm reported earlier. In the second step, these crystalline CoO nanocubes were converted to catalytically active CoP particles through chemical vapor deposition (CVD) phosphorization (denoted as CoP/CFP-H). Remarkably, CoP/CFP-H exhibited a low Tafel slope of 49.7 mV/dec and only required overpotentials of 128.1, 144.4, and 190.8 mV to drive geometric current densities of -10, -20, and -100 mA cm, respectively. Besides, the CoP/CFP-H also demonstrated an excellent durability in an acidi...

Materials Research Letters, 2019

We report the synthesis of a spectrum of highly crystalline molybdenum sulphide/oxide-based mater... more We report the synthesis of a spectrum of highly crystalline molybdenum sulphide/oxide-based materials such as MoS 2 (2-H), MoO 2 and unique hybrid MoS 2 /MoO 2 nanostructures through chemical vapour deposition (CVD). The as-fabricated samples were scrutinized with materials characterization techniques. Our results reveal that, by tuning growth parameters, different samples demonstrate unique morphologies, which can be unequivocally tied to their chemical composition. We also explore their potential application as electrochemical catalysts, which we found that in addition to using large specific surface area and conductive substrate to improve interlayer conductivity,chemical heterogeneity and efficient charge transport are also essential for good catalytic activity. IMPACT STATEMENT We successfully fabricated an array of uniquely shaped MoS 2 /MoO 2 nanostructures through a one-step chemical vapour deposition process. The practical application of said nanostructures as electrochemical catalysts has also been demonstrated.

Journal of Materials Science, 2020

Morphological effects on the electrochemical behaviors of Tin Dioxide (SnO2) have recently been e... more Morphological effects on the electrochemical behaviors of Tin Dioxide (SnO2) have recently been explored in several studies. Nevertheless, the preparations of SnO2 in those works are mostly based on wet-chemistry methods, while the usage of dry-chemistry methods is still lack of investigation. In this work, for the first time, we report the successful fabrication of SnO2 particles attached on carbon fibers via a simple two-step Chemical Vapor Deposition (CVD) approach. CVD growth parameters (temperature, growth time and gas inlet flow rate) were systematically varied to observe the changes in morphologies (in terms of particle density and size distribution) as well as the formation of core–shell Sn/SnO2 structures; and the electrochemical properties of the as-synthesized samples were studied. Our experiments indicate strong correlations among the synthesis conditions, morphologies and electrochemical behaviors. Overall, our findings provide new insights into CVD as a morphological tailoring approach for electrochemical applications—in addition to its simple apparatus and short synthesizing duration, the process is easily extendable for the preparation of other metal and metal oxide particles.

Advanced Science, 2020

Present challenges in electrochromic devices include the limited transmissive and reflective inte... more Present challenges in electrochromic devices include the limited transmissive and reflective inter-switchability, while achieving high optical contrast, fast switching speed, and cycling stability, simultaneously. In article number 1903198, Pooi See Lee and co-workers develop a quasi-solid-state tristate reversible electrochemical mirror device, which offers highly reversible switching between transparent, greyish-blue, and mirror (reflective) optical states. The alloying approach facilitates the electrodeposition and dissolution of Cu mirror film, allowing enhanced device stability.

ACS Applied Energy Materials, 2018

In this work, we report a simple one-step hydrothermal method to fabricate cobalt (Co) doped vana... more In this work, we report a simple one-step hydrothermal method to fabricate cobalt (Co) doped vanadium diselenide (VSe 2) nanosheets on a carbon cloth (CC) for hydrogen evolution reaction (HER) in acid solution. We find that the Co-doped VSe 2 shows significantly enhanced catalytic activity compared with the pristine VSe 2 , including low overpotential of 230 mV at 10 mA/cm 2 , small Tafel slope of 63.4 mV/dec and high stability. Our density-functional-theory (DFT) calculations show that Co dopants dramatically reduce the Gibbs free energy for hydrogen adsorption (ΔG H), leading to improved catalytic activity for hydrogen evolution. Moreover, the Co-doping promotes electron transfer and HER kinetics. Our results provide a valuable route to improve the catalytic performance of metal diselenide in hydrogen evolution reaction.

The Journal of Physical Chemistry Letters, 2018

Reduced molybdenum oxide, generally MoO 3−x , becomes increasingly metallic as the oxygen level d... more Reduced molybdenum oxide, generally MoO 3−x , becomes increasingly metallic as the oxygen level decreases during the reduction of MoO 3 to MoO 2. Its interesting properties have recently intrigued research on MoO 3−x in electrical and electrochemical areas. Lacking effective tools to control the oxygen level is one of the research difficulties for MoO 3−x. Herein, we report facile temperaturecontrolled synthesis of triangular MoO 2 and square Mo 4 O 11. The triangular and square flakes showed metallic behavior with conductivity as high as ∼940 and ∼28 S/cm in DC measurement, respectively. The decrease in oxygen level from Mo 4 O 11 to MoO 2 affected the density of states mapped in Mo 4d orbitals, leading to higher conductivity for triangular MoO 2. Further Mott−Schottky analysis on MoO 3−x regrown on carbon fiber paper (CFP) revealed hole mobility of 10 5 −10 8 cm 2 V −1 s −1. The hole carriers at high frequencies are attributed to potential oxygen acceptors, and molybdenum vacancies resulted from limited reduction power of hydrogen.

Carbon Letters, 2020

We report a simple procedure to fabricate single crystals 3D C 60 having an FCC structure on sili... more We report a simple procedure to fabricate single crystals 3D C 60 having an FCC structure on silicon substrates using a vapour-solid setup in vacuum conditions. The morphology of the deposited film can be tuned by controlling the temperature and position of the substrate. The as-fabricated samples are extensively characterised by transmission electron microscopy, scanning electron microscope, X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation, which allow us to shed light on the recrystallization process of the C 60. In addition, the growth mechanism of the formation of crystalline 3D structure of the C 60 film is discussed in detail. Based on the newly gained knowledge of mechanism and its unique properties, fullerene has shown huge potential as a solid lubricant on various kinds of substrates.

Electrochimica Acta, 2021

Abstracts In this work, we highlight the significances of Controlled Surface Sulfidation (CSS) fo... more Abstracts In this work, we highlight the significances of Controlled Surface Sulfidation (CSS) for high-current-density hydrogen evolution reaction (HER) with bimetallic NiMoO4 microcuboids supported on Ni foam. It reveals that a new phase 1T’-MoS2 is derived in-situ from the surface NiMoO4 microcuboids during CSS in addition to pyrite-phase NiS2 and 2H-MoS2 as obtained from full sulfidation. We denote the controlled sulfided sample as “CSS-NiS2/MoS2” and the fully sulfided sample as “FS-NiS2/MoS2”, respectively. The CSS-NiS2/MoS2 electrode only required low overpotentials of 12, 47, 112 mV to drive -10, -20, -100 mA cm−2, respectively, which surpasses the FS-NiS2/MoS2 considerably (54, 90, 195 mV at -10, -20, -100 mA cm−2, respectively). Notably, it delivers a high current density of -500 and -1000 mA cm−2 at low overpotentials of only 200 and 264 mV, respectively. The durability of the high-current-density activity of CSS-NiS2/MoS2 is also proven over 50 h of stability test. The excellent performances of CSS-NiS2/MoS2 may be synergistically contributed from the active phases and the design dual hierarchical (i.e., 2D-nano/1D-microhybrids) structure. The CSS may serve as an effective strategy to modulate the electrochemical properties of materials holding great promises for the applications of next-generation energy storage and conversion.