Efficient Visible-Light Photocatalytic Hydrogen Evolution over the In2O3@Ni2P Heterojunction of an In-Based Metal-Organic Framework.

Although the engineering of visible-light-driven photocatalysts with appropriate bandgap structures is beneficial for generating hydrogen (H2), the construction of heterojunctions and energy band matching are extremely challenging. In this study, In2O3@Ni2P (IO@NP) heterojunctions are attained by annealing MIL-68(In) and combining the resulting material with NP via a simple hydrothermal method. Visible-light photocatalysis experiments validate that the optimized IO@NP heterojunction exhibits a dramatically improved H2 release rate of 2485.5 µmol g-1 h-1 of 92.4 times higher than that of IO. Optical characterization reveals that the doping of IO with an NP component promotes the rapid separation of photo-induced carriers and enables the capture of visible light. Moreover, the interfacial effects of the IO@NP heterojunction and synergistic interaction between IO and NP that arises through their close contact mean that plentiful active centers are available to reactants. Notably, eosin Y (EY) acts as a sacrificial photosensitizer and has a significant effect on the rate of H2 generation under visible light irradiation, which is an aspect that needs further improvement. Overall, this study describes a feasible approach for synthesizing promising IO-based heterojunctions for use in practical photocatalysis.

High-Performance Visible-Light Photocatalysts for H2 Production: Rod-Shaped Co3O4/CoO/Co2P Heterojunction Derived from Co-MOF-74.

Photocatalyst systems generally consist of catalysts and cocatalysts to realize light capture, charge carrier migration, and surface redox reactions. Developing a single photocatalyst that performs all functions while minimizing efficiency loss is extremely challenging. Herein, rod-shaped photocatalysts Co3O4/CoO/Co2P are designed and prepared using Co-MOF-74 as a template, which displays an outstanding H2 generation rate of 6.00 mmol·g-1·h-1 when exposed to visible light irradiation. It is 12.8 times higher than pure Co3O4. Under light excitation, the photoinduced electrons migrate from the catalysts of Co3O4 and CoO to the cocatalyst Co2P. The trapped electrons can subsequently undergo a reduction reaction to produce H2 on the surface. Density functional theory calculations and spectroscopic measurements reveal that enhanced performance results from the extended lifetime of photogenerated carriers and higher charge transfer efficiency. The ingenious structure and interface design presented in this study may guide the general synthesis of metal oxide/metal phosphide homometallic composites for photocatalysis.