A 1D/2D WO3 nanostructure coupled with a nanoparticulate CuO cocatalyst for enhancing solar-driven CO2 photoreduction: the impact of the crystal facet

Abstract

Photocatalytic reduction of CO₂ into solar fuels is regarded as one of the most promising approaches to address the issues of global warming and the energy crisis. The promotion of spatial charge separation and transfer through crystal facet engineering could be conducive to improved photocatalytic activity. In this study, one-dimensional (1D) WO₃ nanowires with a {110} dominant facet (WO₃-110) and two-dimensional (2D) WO₃ nanosheets with a {001} dominant facet (WO₃-001) coupled with CuO nanoparticles are fabricated by a facile method and used for CO₂ photoreduction. Its composition and structural characterizations suggest that the WO₃–CuO hybrid features good contact between the WO₃ and CuO nanostructures. Under light irradiation, the WO₃ and WO₃–CuO nanostructures are able to photoreduce CO₂ into CH₄. Notably, the prepared WO₃–CuO nanohybrids with different exposed facets show improved CO₂ reduction capability compared to pure WO₃ and CuO. The heterojunction interface between the WO₃ photocatalyst and the CuO cocatalyst through p–n contact can facilitate electron–hole pair separation and accordingly results in enhanced photocatalytic performance. With the assistance of the CuO cocatalyst, the {110} facet WO₃–CuO hybrid displays superior photoreduction capability compared to the {001} facet WO₃–CuO, which is attributed to the difference in the crystal facets in the heterostructure. The {110} facet WO₃ nanowires have a more negative conduction band edge, contributing to the higher reduction capacity of this sample. On the other hand, it is shown that faster charge carrier transfer efficiency would enable more photoinduced electrons to participate in CO₂ photoreduction, especially with the involvement of the nanoparticulate CuO cocatalyst. This work provides guidance for designing a hetero-photocatalyst–cocatalyst system through crystal facet engineering.