Mechanism and thermodynamic study of solar H2 production on LaFeO3 defected surface: Effect of H2O to H2 conversion ratio and kinetics on optimization of energy conversion efficiency

Owing to favorable water-splitting activity at low concentration of steam, LaFeO3 represents promising solar thermochemical (STC) materials to achieve commercial energy conversion efficiency (eta(solar-to-fuel)) of 20%, which is far from reaching up to now. Here we propose possible strategy to improve eta(solar-to-fuel) of LaFeO3 via solving the scarcity of its water-splitting kinetic and thermodynamic characteristics. The detailed pathway of water-splitting and H-2 production around oxygen vacancy site of LaFeO3 is firstly revealed, where the migration of surface H atom is determined as rate controlling step with activation energy of 147.24 kJ/mol. Then, within the good consistent between our thermodynamic calculations and previous experiments, we find that both reduction and water-splitting steps are endothermic, and the conversion ratio of water to hydrogen should be larger than 10% to ensure eta(solar-to-fuel)>20%. In addition, the calculated eta(solar-to-fuel) with the consideration of water-splitting kinetics shows that only the isothermal condition of 1400 K is beneficial for increasing eta(solar-to-fuel) up to 20%. Our work demonstrates the potential of LaFeO3 in efficient H-2 production and provides key metrics for further improvement along the pathway to commercialization. (c) 2020 Elsevier Ltd. All rights reserved.