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 CH₄-introduced solar thermochemical cycle based on MoO₂/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, MoO₂:CH₄ = 2 and 1020 K < T_red < 1600 K are found to be most favorable for syngas selectivity and methane conversion. Compared to the STC cycle without CH₄, 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 H₂O: 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_red = 1200 K and T_oxi = 400 K, indicating that MoO₂ could be a new and potential candidate for obtaining solar fuel by methane reduction.

中文翻译：

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基于MoO 2 / Mo的甲烷还原通过太阳热化学循环制氢的热力学评估

受基于非化学计量氧化物的太阳能热化学（STC）循环中有希望的氢气生产以及甲烷还原的工作温度降低效果的启发，基于MoO ₂ / Mo的高燃料选择性和CH ₄引入的太阳能热化学循环被研究。通过执行HSC模拟，比较了等温和非等温运行条件下的能量提升和能量转换潜力。在还原步骤中，发现MoO ₂：CH ₄ = 2且1020 K < T _red <1600 K最有利于合成气选择性和甲烷转化。与没有CH ₄的STC周期相比，甲烷的引入会产生更高的氢气产量，尤其是在较低温度范围和大气压下。在氧化步骤中，无论是等温还是非等温运行，尤其是在H ₂ O：Mo = 4时，适度过量的水都有利于能量转换。在整个STC循环中，最大非等温和等温效率可以达到0.417和0.391。另外，在T _red = 1200 K和T _oxi = 400 K时，第二个循环的预测效率也高达0.454 ，这表明MoO ₂可能是通过甲烷还原获得太阳能的新的潜在候选者。