Co Nanoparticles on MnO: Electron Transfer through Ohmic and S-Scheme Heterojunction for Photocatalytic Hydrogen Evolution.

The photocatalytic hydrolysis method represents a significant potential solution to the dual challenges of energy security and environmental sustainability. The selection of suitable photocatalytic materials and systems is of paramount importance for the successful implementation of photocatalytic hydrogen production technology. In this study, in situ reduction of Co nanoparticles on MnO was successfully performed by calcining MnCo-PBA. Furthermore, graphdiyne (GDY) was successfully introduced by physical agitation. The introduction of GDY reduced Co/MnO agglomeration and made the Co/MnO/GDY catalyst exhibit high activity in hydrogen production, with an optimum production rate of 2117.33 μmol·g^-1·h^-1, which was 4.88 and 2.67 times higher than that of GDY and Co/MnO, respectively. The results of the photoelectrochemical test indicate that the composite catalyst has a better photogenerated carrier separation efficiency. In situ X-ray photoelectron spectroscopy, density functional theory calculations, and electron paramagnetic resonance were used to investigate the electron transfer mechanism during the photocatalytic process, confirming the presence of an S-scheme heterojunction and an ohmic junction, which enhance the separation of photogenerated carriers. The GDY-based heterojunction catalyst constructed in this study has the potential to significantly enhance the hydrogen production activity of bimetallic catalysts.