Crystal phase engineering boosted photo-electrochemical kinetics of CoSe 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 CoSe. In electrocatalytic reaction, we firstly found that CoSe with orthorhombic phase (o-CoSe) showed a higher OER performance than that of CoSe with cubic phase (c-CoSe). In the further exploration of photocatalytic application using FeO as light harvester and CoSe as cocatalysts, o-CoSe/FeO can realize the qualitative changes of photocatalytic oxygen evolution performance from "0″ to "1". As contrast, c-CoSe/FeO 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 HO on o-CoSe surface. This work opens up an opportunity of correlating the CoSe crystal phase with performance in OER.