N-Doped Carbon Layer Encapsulated NiPx for Photocatalytic Alcohol Oxidation Coupled Hydrogen Evolution on Ag–In–Zn–S Quantum Dots

The photocatalytic oxidation of alcohols to value-added chemicals with simultaneous hydrogen (H 2 ) generation is a promising sustainable process that suffers from slow charge transfer and poor integration of both reactions. Here, an NH 2 -containing Ni metal–organic framework (MOF) is used as a precursor for creating N-doped C layer encapsulated nickel phosphide (NiP x @NC), which effectively enhances the charge transfer and reaction coupling when modified on narrow-band-gap Ag–In–Zn–S quantum dots (AIZS QDs). The resulting AIZS/NiP x @NC photocatalysts demonstrate high efficiency for benzyl alcohol (BA) oxidation coupled H 2 evolution, achieving H 2 /benzaldehyde production rates of 9.66/5.67 mmol g –1 h –1, which are 3.30 and 47.25 times higher than those of pure AIZS QDs, respectively. Additionally, the selectivity of benzaldehyde is enhanced to 77.96%. AIZS/NiP x @NC also shows improved performance for other organics, including 4-methoxybenzyl alcohol and biomass-derived furfuryl alcohol. Photoelectrochemical and transient photovoltage spectroscopy tests confirm the increased effective surface charges and charge transfer efficiency, while electron paramagnetic resonance spectroscopy reveals a carbon-centered radical pathway for selective benzaldehyde formation. DFT calculations suggest that the N-doped carbon enhances the proton adsorption on Ni sites and BA adsorption on the NiP x @NC surface. This work highlights the potential of multifunction integration in developing carbon-based cocatalysts for photocatalytic alcohol oxidation coupled H 2 evolution.