Boosting Photothermal Methanol-to-Hydrogen Efficiency on Cu/ZnO Catalysts by Morphology-Induced Oxygen Vacancy Engineering

Abstract

Photothermal methanol steam reforming (MSR) offers a promising route for efficient hydrogen production. However, the design of high-performance non-precious metal catalysts remains a challenge. In this work, a series of Cu/ZnO catalysts with controlled morphologies (nanoflowers, nanoballs, nanosheets, and nanorods) were synthesized via a facile hydrothermal method and evaluated in photothermal MSR for hydrogen production. Among them, the nanoflower-like Cu/ZnO-F exhibited outstanding catalytic performance, achieving 94.65% methanol conversion, a high H2 production rate of 98 mL·g–1·min–1, and the highest CO2 selectivity (97%) under photothermal conditions (240 °C, WHSV = 17,600 mL/(g·h), 0.1 MPa). Comprehensive characterization (X-ray diffraction (XRD), scanning electron microscopy (SEM), H2-TPR, X-ray photolectron spectroscopy (XPS), ultraviolet-visible (UV–vis) spectroscopy, N2O titration, X-ray absorption spectroscopy (XAS), and N2 adsorption–desorption at low temperature) coupled with density functional theory (DFT) calculations revealed that the superior activity originated from the unique morphology-induced high specific surface area and abundant oxygen vacancies, which collectively stabilized metallic Cu0 species, enhanced Cu dispersion, and facilitated interfacial charge transfer. Furthermore, the synergy between oxygen vacancy-mediated electronic coupling and localized surface plasmon resonance (LSPR) promoted hot-electron injection, lowered the work function, and reduced the energy barrier of the rate-determining step (*CH3O → *CH2O). This work demonstrated that morphology and defect engineering can effectively overcome the limitations of conventional thermal catalysis, providing an energy-efficient photothermal strategy for low-temperature hydrogen production and a viable design route for advanced catalysts in sustainable energy conversion.