  Solar thermochemical hydrogen production (STCH) is a renewable alternative to
hydrogen produced using fossil fuels. While traditional serial bulk
experimental methods can accurately identify promising STCH candidates like
CeO2, they are quite slow for chemically complex material spaces like
perovskites. Here we identify double-site Ce-substituted (Ba, Sr)MnO3 oxide
perovskites as promising candidates for future STCH applications using both
traditional bulk synthesis and high-throughput thin-film experiments.
Single-site Ce-substitution on B site in 10H-BaMnO3 and on A site in 4P-SrMnO3
leads to 300-400C lower reduction temperature and 5-8x higher extent of
reduction in bulk powders compared to CeO2 but still suffers from incomplete
reoxidation. Double-site Ce substitution on both A- and B-site in (Ba, Sr)MnO3
thin films extends the stability range of the 10H and 4P structures, which is
promising for their thermochemical reversibility. This study also demonstrates
a high-throughput experimental method for screening complex oxide materials for
STCH applications.
