Water electrolysis is one of the crucial means for converting electricity generated from solar and wind based power sources into clean H₂ fuels. The efficiency of this process depends largely on the catalytic property of the cathode and anode. We present here our work to develop and understand electrocatalysts used for the oxygen (OER) and hydrogen (HER) evolution reactions. Using operando Raman spectroscopy, we shall first show how the structure of amorphous MoS_x (an excellent HER catalyst) evolves during H₂ evolution. Furthermore, we have identified the S atoms therein as the catalytically active sites responsible for proton reduction. Density functional theory calculations were performed on a variety of MoS_x structures and corroborated the assignments of the observed vibrational frequencies. We shall also present our Raman and X-ray absorption spectroscopy study of Cu oxides during O₂ evolution. This investigation has allowed us to propose Cu^IIIoxides as highly active catalytic species for the electrochemical water oxidation. Mixed metal composites based on Mo and W have also been shown to exhibit excellent HER activities. We elucidated the catalytic roles of the different elements therein such as nitrogen, carbon, molybdenum, etc , and proposed plausible mechanisms of their workings. We shall show that some of these catalysts are robust against deactivation even in contaminated electrolytes. Finally, we present an overview of our recent work to couple photovoltaics to an electrocatalytic cell for the efficient reduction of carbon dioxide.

1. Y.L. Deng, L.R.L. Ting, P.H.L. Neo, Y.J. Zhang, A.A. Peterson, and B.S. Yeo. ACS Catal. 6, 7790. 2016.

2. Y.L. Deng, A.D. Handoko, Y.H. Du, S.B. Xi and B.S. Yeo. ACS Catal. 6, 2473. 2016

3. L.R.L. Ting, Y.L. Deng, L. Ma, Y.J. Zhang, A.A. Peterson, and B.S. Yeo. ACS Catal. 6, 861. 2016

4. U. Joshi, J. Lee, C. Giordano, S. Malkhandi and B.S. Yeo.  Phys. Chem. Chem. Phys. 18, 21548. 2016.