21^st World Nanotechnology Congress

Hydrogen (H2) has been proposed to be a clean and carbon-neutral energy carrier that can be used as next-generation fuel to fulfill both stationary and transportation needs. Compared to steam reforming, electro-catalytic water splitting represents a greener and more sustainable way for H₂ generation and has been intensively investigated in recent years. The Oxygen Evolution Reaction (OER) has been a bottleneck to improve water splitting effi ciency. It involves four concerted proton-coupled electron transfer steps and is both thermodynamically and kinetically demanding. Without a catalyst, the OER

usually takes place at a high over-potential leading to a large energy loss. Compared to the OER, the H₂ Evolution Reaction (HER) can be accomplished comparatively easily, but efficient electro-catalysts are still needed to reduce the over-potential for HER and enable the reaction to take place at a practically high rate. Lately, earth-abundant transition metal based electrocatalysts

have been demonstrated to be highly active for both HER and OER and are proposed to be promising alternatives to Platinum Group Metal (PGM) catalysts for use in water electrolysers. In this study, we showed our recent efforts to developing efficient and durable transition metal based electrocatalysts, including transition metal phosphides obtained by wet chemical reduction followed by post-phosphorization treatment and cobalt ultrafi ne clusters prepared by cluster beam deposition. We have demonstrated that all these catalysts show electro-catalytic performance favorably compared to PGM based electrocatalysts for HER or OER and therefore hold substantial promise for use as low-cost catalysts in water electrolysers.