  Solar thermochemical hydrogen production (STCH) is a renewable alternative to
hydrogen produced using fossil fuels. While serial bulk experimental methods
can accurately measure STCH performance, screening chemically complex materials
systems for new promising candidates is more challenging. Here we identify
double-site Ce-substituted (Ba,Sr)MnO3 oxide perovskites as promising STCH
candidates using a combination of bulk synthesis and high-throughput thin film
experiments. The Ce substitution on the B-site in 10H-BaMnO3 and on the A-site
in 4P-SrMnO3 lead to 2-3x higher hydrogen production compared to CeO2, but
these bulk single-site substituted perovskites suffer from incomplete
reoxidation. Double-site Ce substitution on both A- and B-site in (Ba,Sr)MnO3
thin films increases Ce solubility and extends the stability of 10H and 4P
structures, which is promising for their thermochemical reversibility. This
study demonstrates a high-throughput experimental method for screening complex
oxide materials for STCH applications.
