Efficient All-Earth-Abundant Cu ₂ O-CuO Heterostructure Photocathode Decorated with Large Surface-Area MOF-Derived MoS ₂ –TiO ₂ Nanohybrids for Enhanced Solar Water Splitting

The scalability of solar-driven photoelectrochemical (PEC) water splitting is limited by the dependence on scarce noble metals in conventional photocathodes. This study presents a cost-effective, noble-metal-free approach by integrating a Cu2O-CuO nanoflake (Cu2O-CuO-NF) heterostructure with metal–organic framework (MOF)-derived MoS2–TiO2 (m-MoS2–TiO2) nanohybrid cocatalysts synthesized through a one-step hydrothermal method. The innovation lies in the use of MOF-derived m-MoS2–TiO2, whose high surface area, tunable porosity, and abundant active sites significantly enhance PEC performance. Decorating electrodeposited Cu2O-CuO-NF with m-MoS2–TiO2 yields a photocurrent density of −3.93 mA cm–2 at −0.6 V vs Ag/AgCl, representing a 35-fold improvement over bare Cu2O. The Cu2O-CuO-NF/m-MoS2–TiO2 photocathode also produces 103.8 μmol cm–2 of H2 in 2 h with a Faradaic efficiency of 90%. Field emission scanning electron microscopy (FE-SEM) confirms suppression of CuO self-reduction, attributed to the formation of a p–n heterojunction between Cu2O-CuO-NF and m-MoS2–TiO2, as supported by Mott–Schottky and EIS analyses. MoS2 facilitates electron transfer from Cu2O-CuO-NF to TiO2, promoting H2 evolution reaction (HER) and reducing recombination. The cocatalyst also increases surface area (1.8-fold compared to pristine Cu2O-CuO-NF) and provides corrosion protection, improving stability. This combination of improved charge dynamics and stability clearly showcases the potential of MOF-derived cocatalysts in advancing sustainable H2 production through an earth-abundant and scalable approach.