Abstract
AbstractThe development of phase engineering still confronts challenges including controlled synthesis of desired phase structures and unraveling of inner mechanism for phaseâdependent applications. Herein, taking CoSe2 as a prototype, a facile wetâchemical method is developed to synthesize metastable orthorhombic phase CoSe2 (oâCoSe2). In the meantime, stable cubic phase CoSe2 (câCoSe2) can be prepared by phase transition from oâCoSe2 using a general annealing approach. It is demonstrated that CoSe2 exhibits distinct phaseâdependent hydrogen evolution performance in photoâ and electrocatalysis. In electrocatalytic reaction, oâCoSe2 shows an overpotential of 300 mV better than câCoSe2 (365 mV) at â10 mA cmâ2 in acid solution. Unlike electrocatalysis, as cocatalyst in photocatalytic hydrogen evolution, câCoSe2/TiO2 exhibits a roughly 4.5âfolds higher hydrogen evolution rate (12.001 ”mol hâ1) than oâCoSe2/TiO2 (2.601 ”mol hâ1). Combined with comprehensive theoretical and experimental analysis, it has been proposed that appropriate hydrogen adsorption ability of oâCoSe2 contributes to efficient electrocatalysis, whilst fast interfacial charge migration between TiO2 photoâharvester and câCoSe2 cocatalyst is the dominating factor for photocatalysis. This article demonstrates the feasibility of improving catalytic activity of CoSe2 by phase engineering, and also, provides guidance into unmasking the relationship between phase structure and hydrogen evolution catalysis.
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