The role of titanium at the interface of hematite photoanode in multisite mechanism:Reactive site or cocatalyst site?
Hematite(α-Fe2O3)constitutes one of the most promising photoanode materials for oxygen evolu-tion reaction(OER).Recent research on Fe2O3 have found a fast OER rate dependence on surface hole density,suggesting a multisite reaction pathway.However,the effect of heteroatom in Fe2O3 on the multisite mechanism is still poorly understood.Herein we synthesized Fe2O3 on Ti substrates(Fe2O3/Ti)to study the oxygen intermediates of OER by light-dark electrochemical scans.We identi-fied the Fe-OH species disappeared and Ti-OH intermediates appeared on Fe2O3/Ti when pH=11-14,which significantly improved the OER performance of Fe2O3/Ti.Combined with the density functional theory calculations,we propose that Ti atom acts as cocatalyst site and captures proton from neighboring Fe-OH species under highly alkaline condition,thereby promoting the coupling of Fe=O and reducing the energy barrier of the non-electrochemical step.Our work provides a new insight into the role of heteroatom in OER multisite mechanism based on clarifying the reaction intermediates.
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