Synergistic etching-phosphorylation engineered hollow CoP photocatalysts for boosted photocatalytic hydrogen evolution

Abstract

The recombination rate of photogenerated charge carriers and the light response capacity are pivotal factors influencing the photocatalytic activity of photocatalysts. In this work, a series of hollow-structured amorphous CoP photocatalysts (denoted as TA-CoP-x) with tunable bandgap structures were successfully synthesized by selective etching using tannic acid (TA) and gradient phosphorating for photocatalytic hydrogen evolution. The hollow architecture of CoP substantially increases the exposure of active sites and promotes proton diffusion dynamics, that favor proton reduction for enhancing photocatalytic hydrogen evolution. Bandgap structure analysis revealed that phosphatization induces a continuous negative shift in the conduction band of TA-CoP-x, thereby enhancing its proton reduction capability. The synergistic effect of the hollow structure and phosphorating enables TA-CoP-x with the ability to effectively separate and transfer photogenerated charge carriers while expanding the visible light absorption range, resulting in progressively enhanced photocatalytic activity. Consequently, TA-CoP-5 shows the highest hydrogen evolution rate of 13.59 mmol g^-1 h^-1, which is 3.29 times higher than that of the TA-ZIF-67. This work provides a new approach to design hollow CoP with different band gaps by combining chemical etching and phosphating for enhancing the photocatalytic efficiency.