Charting Ba-Based Double Perovskite Oxides for Visible-Light-Driven Photocatalytic Water Splitting

Realizing green hydrogen generation is contingent on developing low-cost, ecofriendly, and viable photocatalysts for water splitting. Using first-principles screening, we filtered out several Ba-based double perovskites (i.e., Ba₂BB′O₆) that are desired for such applications. Detailed chemical and electronic structure analyses reveal that all of the studied double perovskites, despite their disparate compositions, fall into five classes, depending on the orbital occupancy of the B and B′ cations. Of the five different classes, class I with the B = B′ = d¹⁰s⁰ electronic configuration has proper band gap ranges (1.4–2.8 eV) and significant optical absorption coefficients, making them viable photocatalysts for visible-light-driven one- and two-photon water-splitting reactions. Among the materials examined, Ba₂AgIO₆, Ba₂CdTeO₆, Ba₂InSbO₆, and Ba₂BiSbO₆, the only class V materials, stand out for their favorable optical absorptions and low exciton binding energies. The other classes include perovskites with large band gaps (>3 eV) that are suggested as transparent anode and cathode shields to protect photocatalysts from corrosion. Our findings provide valuable insights into exploring a rich family of nontoxic, highly effective Ba-based double perovskites for photocatalytic water-splitting applications.