Fabrication of hierarchical Co3O4@CdIn2S4 p–n heterojunction photocatalysts for improved CO2 reduction with visible light

Abstract

Hierarchical Co₃O₄@CdIn₂S₄ p–n heterojunction photocatalysts, composed of ultrathin CdIn₂S₄ nanosheets supported on Co₃O₄ nanocubes, have been assembled through a facile solvothermal method for efficient CO₂ reduction with visible light. The solution-processed surface growth strategy is advantageous to form an intimately coupled interface in situ for the Co₃O₄@CdIn₂S₄ hybrids with easily controllable compositions. Diverse physicochemical characterization experiments reveal that the Co₃O₄@CdIn₂S₄ heterostructures have more catalytically active sites, increased CO₂ adsorption, as well as hampered recombination and accelerated separation and mobility of photoexcited charge carriers. As a result, the Co₃O₄@CdIn₂S₄ p–n heterojunction photocatalysts display greatly improved activity compared to their nanosheet-assembled CdIn₂S₄ counterpart, affording an optimal CO generation rate of 53 μmol h⁻¹ (i.e., 5300 μmol h⁻¹ g⁻¹) and a high CO selectivity of 93.3%. Besides, the optimized Co₃O₄@CdIn₂S₄ photocatalyst has a high apparent quantum efficiency (AQE) of 1.87% under monochromatic light irradiation at 420 nm. Importantly, such metal sulfide composite photocatalysts also exhibit excellent stability against photocorrosion, due to the efficient hole transfer from CdIn₂S₄ to Co₃O₄. On the basis of the band structures and catalytic evaluation results, a possible CO₂ photoreduction mechanism is further proposed.