Crystal phase engineering boosted photo-electrochemical kinetics of CoSe₂ for oxygen evolution catalysis

Crystal phase is an important parameter that can determine the electronic structure and catalytic properties of catalysts. In this work, we report the crystal phase dependent photo- and electrocatalytic oxygen evolution reaction (OER) performance of CoSe₂. In electrocatalytic reaction, we firstly found that CoSe₂ with orthorhombic phase (o-CoSe₂) showed a higher OER performance than that of CoSe₂ with cubic phase (c-CoSe₂). In the further exploration of photocatalytic application using Fe₂O₃ as light harvester and CoSe₂ as cocatalysts, o-CoSe₂/Fe₂O₃ can realize the qualitative changes of photocatalytic oxygen evolution performance from "0″ to "1". As contrast, c-CoSe₂/Fe₂O₃ cannot work in photocatalytic oxygen evolution process under the same condition. Experimental and theoretical analysis uncover that, the key factor leading to the crystal phase-dependent performance is the decreased activation barrier of H₂O on o-CoSe₂ surface. This work opens up an opportunity of correlating the CoSe₂ crystal phase with performance in OER.