DataSheet1_A Thermogravimetric Temperature-Programmed Thermal Redox Protocol for Rapid Screening of Metal Oxides for Solar Thermochemical Hydrogen Production.docx

As combinatorial and computational methods accelerate the identification of potentially suitable thermochemically-active oxides for use in solar thermochemical hydrogen production (STCH), the onus shifts to quickly evaluating predicted performance. Traditionally, this has required an experimental setup capable of directly carrying out a two-stage thermochemical water-splitting process. But this can be a difficult endeavor, as most off-the-shelf equipment cannot adequately deal simultaneously with the high temperatures, varying oxygen partial pressures, and high H2O partial pressures required; achieving sufficient temporal sensitivity to accurately quantify the kinetics is also a major challenge. However, as proposed here, a less complicated experiment can be used as a first screening for thermochemical water splitting potential. Temperature-Programmed Thermal Redox (TPTR) using thermogravimetry evaluates the thermal reduction behavior of materials. This technique does not require water splitting or CO2-splitting analogs but can nonetheless predict water-splitting performance. Three figures of merit are obtained from the TPTR experiment: reduction onset temperature, extent of reduction, and extent of recovery upon reoxidation. These metrics can collectively be used to determine if a material is capable of thermochemical water-splitting, and, to good approximation, predict whether the thermodynamics are favorable for use under more challenging high-conversion conditions. This paper discusses the pros and cons of using TPTR and proposes a protocol for use within the STCH community.

随着组合与计算方法加速识别适用于太阳能热化学制氢（Solar Thermochemical Hydrogen Production, STCH）的潜在热化学活性氧化物，研究重心随之转向快速评估其预测性能。传统上，此类评估需搭建可直接开展两阶段热化学水分解过程的实验装置，但该工作极具挑战：多数市售通用设备无法同时满足实验所需的高温、变化的氧分压与高水蒸气分压条件；同时，获取足够的时间灵敏度以精确量化反应动力学，亦是一大难题。然而本文提出一种更为简便的实验方案，可用于热化学水分解潜力的初步筛选。采用热重分析法的程序升温热氧化还原（Temperature-Programmed Thermal Redox, TPTR）技术可评估材料的热还原行为。该技术无需开展水分解或二氧化碳分解的模拟实验，却仍可准确预测材料的水分解性能。从TPTR实验中可获得三项性能指标：还原起始温度、还原程度以及再氧化后的恢复程度。上述指标可共同用于判断材料是否具备热化学水分解能力，且可在较高近似程度下，预测材料在更严苛的高转化率条件下的热力学可行性。本文讨论了采用TPTR技术的优缺点，并为STCH领域提出了一套实验方案。