Z-scheme photocatalyst based on porphyrin derivative decorated few-layer BiVO₄ nanosheets for efficient visible-light-driven overall water splitting

It is highly desirable to simulate natural photosynthesis by using sunlight to drive the overall water splitting without using external bias and sacrificial agent. Herein, few-layer monoclinic BiVO₄ nanosheets (BVNS) with a thickness of ~4.3 nm, exposed (010) facets and abundant oxygen vacancies are fabricated using graphene oxide dots as templating reagent. After decorating with asymmetric chromium porphyrin derivative bearing one benzoic acid and three phenyls as meso-position substituents (chromium-5-(4-carboxyphenyl)-10,15,20-triphenylporphrin, CrmTPP) and PtO_x cocatalyst, the obtained two-dimensional (2D) hybrid nanocomposite (BVNS/CrmTPP/Pt) with an optimal component ratio delivers a robust overall water splitting performance with a relatively high apparent quantum yield (8.67%) at 400 nm monochromatic light. The ultrathin structure and widely distributed oxygen vacancies on the exposed (010) facets of BVNS not only endow strong and intimate contact with the decorated CrmTPP molecules to promote a two-step excitation Z-scheme charge transfer mechanism for preserving the high redox ability of the photogenerated charge carriers, but also alleviate their recombination, and thus causing the robust overall water splitting performance of the 2D hybrid nanocomposites. The present results provide a novel strategy to construct highly efficient artificial photosynthetic system for overall water splitting.