Michael K.H. Leung

An efficient bismuth tungstate visible-light-driven photocatalyst for breaking down nitric oxide

This paper reports a photocatalytic removal of 400 ppb level of NO in air under visible light irradiation by utilizing three-dimensional (3D) hierarchical bismuth tungstate (Bi(2)WO(6)) microspheres. A facile microwave-assisted hydrothermal method involving bismuth nitrate and sodium wolframate was developed to synthesize the photocatalyst. The Bi(2)WO(6) samples were characterized by using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Raman and ultraviolet-visible reflectance (UV-vis) spectroscopy. The relationship between the physicochemical property and the photocatalytic performance of the as prepared samples is discussed. The present work demonstrates that the 3D hierarchical Bi(2)WO(6) microspheres are effective visible-light-driven photocatalytic functional materials for air purification.

Engineering stepped edge surface structures of MoS2 sheet stacks to accelerate the hydrogen evolution reaction

Two-dimensional molybdenum sulfide is an attractive noble-metal-free electrocatalyst for the hydrogen evolution reaction (HER). Significant efforts have been made to increase the number of exposed edge sites. However, little attention has been paid to devising edge surface structures of MoS2 sheet stacks to promote the HER kinetics. Herein we report the first demonstration of significantly enhanced HER kinetics by controllably fabricating a stepped MoS2 surface structure. Vertical arrays of MoS2 sheets terminated with such a stepped surface structure have proved to be an outstanding HER electrocatalyst with an overpotential of 104 mV at 10 mA cm−2, an exchange current density of 0.2 mA cm−2 and high stability. Experimental and theoretical results indicate that the enhanced electrocatalytic activity of the vertical MoS2 arrays is associated with the unique vertically terminated, highly exposed, stepped surface structure with a nearly thermoneutral H-adsorption energy. This work opens a new avenue to designing and developing layered materials for electrochemical energy applications.

Barriers to adopting solar photovoltaic systems in Hong Kong

The adoption of solar photovoltaic systems is often constrained by various sociotechnical barriers. In this paper, we identify and differentiate barriers to photovoltaic among three groups of potential adopters in Hong Kong: individuals, businesses, and the public sector. A total of 55 interviews were conducted to collect the data for the study. The results indicate that the most important constraints were technical barriers such as space limitations and low energy output, followed by economic barriers such as high upfront costs and long payback periods. Furthermore, we found that individuals were the group most exposed to market, policy, and regulatory barriers and they had to contend with the highest number of barriers. Our analysis also illustrates that there was a close interrelationship between the barriers. For example, technical barriers, such as space limitations, could be overcome partially by addressing regulatory barriers. Based on the analysis, we formulate a number of policy recommendations. The results of this study could be useful to the government in its attempt to facilitate a sustainable energy transition in Hong Kong.