A Mechanistic and Prototype Study with Solar Photothermal Process Using Hydrotalcite-Like Cu/ZnO/Al ₂ O ₃

Photothermal catalysis integrates photochemical and thermochemical effects, offering a promising pathway for solar-driven methanol steam reforming (MSR). However, traditional catalysts exhibit limited light utilization and insufficient low-temperature activity, and most studies remain at the laboratory scale under simulated light without on-sun performance testing. In this work, a hydrotalcite-like Cu/ZnO/Al2O3 catalyst is developed, with performance evaluated through laboratory experiments and on-sun prototype testing at a scale of 2.5 Nm3·h–1. The layered structure of the catalyst enables broadband light absorption and enhances low-temperature performance. Under indoor illumination at 180 °C, the optimized catalyst achieves a methanol conversion of 78.9% and a H2 production rate of 14.2 μmol·g–1·s–1. These represent relative increases of 163.9% and 173.1% over thermocatalysis, while reducing the reaction temperature by approximately 40 °C. The catalyst maintains stable activity during a 10 h test. Mechanistic studies reveal that the layered hydrotalcite-like structure and strong Cu-ZnO interaction enhance light absorption and charge transfer, lowering the apparent activation energy under illumination by 80.7%. In situ DRIFTs analysis indicates that illumination promotes the formation and conversion of key intermediates, facilitating methanol activation. Furthermore, the catalyst is tested on a trough solar photothermal prototype under on-sun conditions. It achieves a methanol conversion of 78.1% and a hydrogen production rate of 2.5 Nm3·h–1 during 1.5 h of continuous operation. The H2/CO2 ratio remains near the theoretical 3:1 stoichiometry, demonstrating stability and high selectivity. This work, from mechanistic study to on-sun testing, highlights the potential of photothermal MSR for practical production of sustainable solar fuels.