Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

Dawei Zhang; Hector A. De Santiago; Boyuan Xu; Cijie Liu; Jamie Trindell; Wei Li; Jiyun Park; Mark A. Rodriguez; Eric N. Coker; Josh Sugar; Anthony McDaniel; Stephan Lany; Liang Ma; Yi Wang; Gregory Collins; Hanchen Tian; Wenyuan Li; Yue Qi; Xingbo Liu; Jian Luo

arXiv · 2209.10704

Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

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Abstract

Solar thermochemical hydrogen generation (STCH) is a promising approach for eco-friendly H2 production, but conventional STCH redox compounds often suffer from thermodynamic and kinetic limitations with limited tunability. Expanding from the nascent high-entropy ceramics field, this study explores a new class of compositionally complex perovskite oxides (La0.8Sr0.2)(Mn(1-x)/3Fe(1-x)/3CoxAl(1-x)/3)O3 for STCH. In situ X-ray diffraction demonstrates the phase stability during redox cycling and in situ X-ray photoelectron spectroscopy shows preferential redox of Co. The extent of reduction increases, but the intrinsic kinetics decreases, with increased Co content. Consequently, (La0.8Sr0.2)(Mn0.2Fe0.2Co0.4Al0.2)O3-{\delta} achieves an optimal balance between the thermodynamics and kinetics properties. The combination of a moderate enthalpy of reduction, high entropy of reduction, and preferable surface oxygen exchange kinetics enables a maximum H2 yield of 395 +- 11 {\mu}mol g-1 in a short 1-hour redox duration. Entropy stabilization expectedly contributes to the structure stability during redox without phase transformation, which enables an exceptional STCH stability for >50 cycles under harsh interrupted conditions. The underlying redox mechanism is further elucidated by the density functional theory based parallel Monte Carlo computation, which represents a new computation paradigm first established here. This study suggests a new class of non-equimolar compositionally complex ceramics for STCH and chemical looping.

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Dawei Zhang, Hector A. De Santiago, Boyuan Xu, Cijie Liu, Jamie Trindell, Wei Li, Jiyun Park, Mark A. Rodriguez, Eric N. Coker, Josh Sugar, Anthony McDaniel, Stephan Lany, Liang Ma, Yi Wang, Gregory Collins, Hanchen Tian, Wenyuan Li, Yue Qi, Xingbo Liu, Jian Luo. 2022-09-21. Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting. https://arxiv.org/abs/2209.10704

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