Thermodynamic assessment of hydrogen production via solar thermochemical cycle based on MoO/Mo by methane reduction

Inspired by the promising hydrogen production in the solar thermochemical (STC) cycle based on non-stoichiometric oxides and the operation temperature decreasing effect of methane reduction, a high-fuel-selectivity and CH-introduced solar thermochemical cycle based on MoO/Mo is studied. By performing HSC simulations, the energy upgradation and energy conversion potential under isothermal and non-isothermal operating conditions are compared. In the reduction step, MoO:CH = 2 and 1020 K < T < 1600 K are found to be most favorable for syngas selectivity and methane conversion. Compared to the STC cycle without CH, the introduction of methane yields a much higher hydrogen production, especially at the lower temperature range and atmospheric pressure. In the oxidation step, a moderately excessive water is beneficial for energy conversion whether in isothermal or non-isothermal operations, especially at HO: Mo = 4. In the whole STC cycle, the maximum non-isothermal and isothermal efficiency can reach 0.417 and 0.391 respectively. In addition, the predicted efficiency of the second cycle is also as high as 0.454 at T = 1200 K and T = 400 K, indicating that MoO could be a new and potential candidate for obtaining solar fuel by methane reduction.