Photocatalytic H2 evolution integrated with selective amines oxidation promoted by NiS2 decorated CdS nanosheets

Photocatalytic hydrogen (H2) evolution integrated with selective oxidation to produce fine chemicals is a promising strategy for solar energy conversion and storage; however, the efficiency of such coupled photocatalytic redox cycles is greatly limited by the poor surface kinetics of hydrogen evolution reaction (HER) and/or dehydrogenation reaction (DHR) on heterogenous photocatalysts. Herein, we demonstrate that the immobilization of ultrafine nickel disulfide (NiS2) nanoparticles on CdS nanosheets (NiS2/CdS) is a simple yet efficient approach to kinetic improve the surface redox reactions for H2 production and dehydrogenative coupling of amines to imines. The NiS2 nanoparticles loaded on CdS not only function as the HER active sites to speed up charge separation and to boost H2 release, but also enhance the adsorption of amines to facilitate the dissociation of C-H and N-H bonds to form aldimines intermediates, which are readily coupled with other amines to afford a high selectivity toward imine synthesis. Benefiting from such unique bifunctional catalytic behavior of NiS2 in proton (H+) reduction and substrate activation, NiS2/CdS exhibits a remarkable enhanced photocatalytic performance toward simultaneous production of H2 and imines. The apparent quantum efficiency (AQE) at 420 nm is calculated to be 54.7%. This strategy using bifunctional cocatalysts to kinetic improve the surface redox reactions will have broad implications in the development of high-performance photocatalysts for integrated production of solar hydrogen and value-added solar chemicals.