Facet-dependent carrier dynamics of cuprous oxide regulating the photocatalytic hydrogen generation

Abstract

The intrinsic carrier dynamics of cuprous oxide (Cu₂O) are known to have a crucial influence on photocatalytic performances. The photoactivity of rhombic dodecahedral Cu₂O with dominant {110} facets (RD-Cu₂O) is demonstrated to surpass that of cubic Cu₂O with {100} surfaces (CB-Cu₂O). Time resolved microwave conductivity (TRMC) measurements reveal the higher carrier mobility of RD-Cu₂O when compared to CB-Cu₂O. Additionally, modulated surface photovoltage (SPV) measurements further supported the better charge separation efficiency of RD-Cu₂O. Although CB-Cu₂O exhibited more pronounce SPV signals, the homogeneous distribution of electrical fields drives the majority charge inward and led to detrimental charge recombination. In contrast, the weak SPV signals for RD-Cu₂O were attributed to a modulated distribution of charges towards the facets and facet boundaries, demonstrating a better charge separation. This study shows that carrier dynamics and defect density should also be regarded as facet-dependent properties that can have deciding influence on the photocatalytic activity.