Redox-Mediated CdS Photocatalytic Panel for Overall Water Splitting with Gas Separation

The critical step to improve the solar-to-hydrogen efficiency of particulate photocatalysis is to exploit semiconducting particles with narrow bandgaps and superior optoelectronic properties. However, group II-VI semiconductors, as a class of promising candidates, are restricted by their photo-instabilities in aqueous environment. Herein, we use a stabilization coating to address the photocorrosion of CdS photocatalysts and then construct a redox-mediated particulate solar-fuel reactor with product separation. Through the design of a highly efficient and stable CdS/TiO₂/ Rh@CrO_x photocatalytic panel, we obtain a H₂ evolution rate of 107.5 μmol∙h^-1∙cm^-2 under ambient condition in a Na₂S solution, which is more than 550 times higher than that of the commercial pristine CdS powders. The semiconductor/protective coating/co-catalyst interface exhibits an adaptive junction behavior, which creates asymmetric barrier height at CdS locally to facilitate lateral charge separation. We achieve water splitting by integrating a photovoltaic-electrolysis cell to regenerate the S^2-/S_n^2- redox mediator and demonstrate stoichiometric H₂ and O₂ evolution with gas separation. The O₂-evolution processes are separated spatially and temporally from photocatalytic H₂ production.