Construction of Full Solar-Spectrum-Driven Cu_2–xS/Ni-Al-LDH Heterostructures for Efficient Photocatalytic CO₂ Reduction

The reduction of CO2 to hydrocarbons through photocatalysis is a promising way to realize "carbon-neutral". Nevertheless, developing efficient photocatalysts to achieve high solar energy conversion efficiency and CO2 conversion efficiency is a challenge. Here, we constructed a defective Cu2-xS/Ni-Al-LDH heterojunction photocatalyst via a hydrothermal method. The designed Cu vacancies in Cu2-xS and multiband transition of layered double hydroxide (LDH) promised its efficient solar energy utilization, showing decent CO2 photoreduction performance in both the full-spectrum and near-infrared (NIR) regions. The optimized 15% Cu2-xS/LDH composite achieved CH4 and CO yields of 14.2 mu mol/g/h (2.83 mu mol/g/h in the NIR region) and 5.3 mu mol/g/h (2.99 mu mol/g/h in the NIR region), respectively. Furthermore, the corresponding apparent quantum efficiency (AQE) of a 15% Cu2-xS/LDH catalyst is 3.86% at 420 nm. Experimental and characterization results suggested that the enhanced CO2 photoreduction performance could be ascribed to the fabricated p-n heterojunction with a Z-scheme charge transfer route between Cu2-xS and LDH, which inhibited the electron-hole recombination and improved the reaction kinetic energy owing to a higher conduction potential. The fabricated binary catalytic system with the nonprecious metal Cu2-xS and LDH has great prospects for realizing cost-efficient CO2 photoreduction.