Cr 2 O 3 Nanoparticles on Ba 5 Ta 4 O 15 as a Noble‐Metal‐Free Oxygen Evolution Co‐Catalyst for Photocatalytic Overall Water Splitting

The (1 1 1)‐layered perovskite material Ba 5 Ta 4 O 15 represents a suitable photoabsorber with remarkable photocatalytic activity in overall water splitting. We are the first to demonstrate overall water splitting without the presence of a noble‐metal‐based co‐catalyst over this catalyst. The photocatalytic activity of Ba 5 Ta 4 O 15 was investigated by overall water splitting after reductive photodeposition of amorphous Cr 2 O 3 . The formation of Cr 2 O 3 nanoparticles for water splitting was evidenced by X‐ray photoelectron spectroscopy and transmission electron microscopy. The reductive photodeposition of very low amounts of Cr 2 O 3 on Ba 5 Ta 4 O 15 induces stable rates in overall water splitting up to 465 μmol h −1 H 2 and 228 μmol h −1 O 2 .