CsPbBr3/CdSe Heterostructures for Photocatalytic CO2 Reduction

Converting CO2 into chemical fuels using sunlight is a promising approach towards addressing the increasing levels of greenhouse gases while reducing our reliance on fossil fuels. Among the many identified photocatalysts to achieve this, metal halide perovskite nanocrystals are a prospective class due to their favourable optoelectronic and structural properties. However, the rapid and efficient radiative recombination, as well as limited CO2 activation by such pristine perovskite nanocrystals, hinders their photocatalytic efficiency. Herein, a ligand-engineering approach is harnessed to develop 0D CsPbBr3 nanocrystal – 2D CdSe nanoplatelet heterostructures to enhance photo-induced carrier separation and improve photocatalytic activity. This is demonstrated through photocurrent and CO2 reduction studies, which yield up to 8-fold-enhancements in CO and CH4 production yields relative to the pristine nanocrystals. Detailed characterisation of these heterostructures suggests that their photocatalytic properties are enabled by a staggered energy level alignment at the CdSe and CsPbBr3 interface, which promotes a built-in electric field of up to 0.5 eV. Electron spin resonance measurements further suggests that the heterojunction operates through a direct Z-scheme mechanism. This work highlights the potential of ligand-assisted heterojunction design in perovskite-based photocatalysts, providing a valuable platform for enhancing solar-to-chemical conversion efficiency.利用太阳光将二氧化碳转化为化学燃料，是应对日益加剧的温室气体排放、降低化石燃料依赖的极具前景的路径。在可实现该过程的诸多已发掘光催化剂（photocatalysts）中，金属卤化物钙钛矿纳米晶（metal halide perovskite nanocrystals）凭借其优异的光电与结构特性，成为极具潜力的一类材料。然而，原始钙钛矿纳米晶存在快速高效的辐射复合，以及有限的CO₂活化能力，这制约了其光催化效率。本研究采用配体工程策略，构建了零维CsPbBr₃纳米晶-二维CdSe纳米片异质结构，以增强光生载流子分离效率并提升光催化活性。通过光电流测试与CO₂还原实验验证了该策略的有效性：相较于原始纳米晶，该异质结构的CO与CH₄生成产率最高提升8倍。对该异质结构的详细表征表明，其光催化性能得益于CdSe与CsPbBr₃界面处的交错能级排布，该排布可形成高达0.5 eV的内建电场。电子自旋共振测量进一步证实，该异质结通过直接Z型机制运行。本研究凸显了配体辅助异质结设计在钙钛矿基光催化剂中的应用潜力，为提升太阳能-化学能转化效率提供了极具价值的研究平台。