Coupled internal electric field with hydrogen release kinetics for promoted photocatalytic hydrogen production through employing carbon coated transition metal as co-catalyst.

The ideal solution to the energy shortage problem is to split water into hydrogen (H2) utilizing solar-driven semiconductor photocatalytic technology. Nevertheless, severe carrier recombination is the major cause of decreased activity over photocatalysts. Construction of internal electric field (IEF) by coupling semiconductor with metal co-catalyst can effectively promote carrier separation. Herein, Co@C with the Co encapsulated in the C layer as a co-catalyst anchored on the surface of ZnIn2S4 nanosheets via a facile electrostatic self-assembly strategy, achieving outstanding photocatalytic water splitting into H2 under simulated solar irradiation (AM 1.5G) with the production rate of 18.1 mmol h-1 g-1, which is 109.7 times higher than that of bare ZIS without assisted of Pt. Enhancement of photocatalytic H2 evolution activity of Co@C/ZIS is mainly attributed to the construction of giant IEF (4.6-fold higher than ZIS) and suitable environment for hydrogen adsorption and desorption (ΔGH* ∼ 0), which endows the following several advantages: (i) accelerating the migration and separation of photo-generated charges; (ii) improving the hydrogen release kinetics. Our work not only provides a design idea for facile preparation of a high-efficient composite photocatalyst, but also expands the application range of transition metal@carbon as a co-catalyst in energy photocatalysis.