Outstanding Properties and Performance of CaTi0.5Mn0.5O3–δ for Solar-Driven Thermochemical Hydrogen Production

A global transition away from fossil fuel energy to sustainable sources, in particular solar energy, requires breakthroughs in energy storage. Two-step solar thermochemical hydrogen (STCH) production, which utilizes the entire solar spectrum, functions in the absence of precious metal catalysis, and yields hydrogen and oxygen separately, has emerged as an attractive route for meeting this demand. Here, we report the thermochemical properties of CaTi0.5Mn0.5O3−δ. The combination of large entropy and moderate enthalpy of reduction, along with rapid material kinetics, results in an outstanding hydrogen productivity of 10 mL g−1 with reduction temperature at just 1,350°C and a short cycle time of 1.5 h. The material furthermore displays excellent thermal stability. Beyond performance metrics, the thermodynamic data connect material chemistry to hydrogen yields for arbitrary cycling conditions, a critical step toward designing materials suitable for widespread commercial adoption.