Highly Efficient Photoelectrochemical Water Splitting with an Immobilized Molecular Co 4 O 4 Cubane Catalyst

Molecular Co 4 O 4 cubane water oxidation catalysts were combined with BiVO 4 electrodes for photoelectrochemical (PEC) water splitting. The results show that tuning the substituent groups on cobalt cubane allows the PEC properties of the final molecular catalyst/BiVO 4 hybrid photoanodes to be tailored. Upon loading a new cubane complex featuring alkoxy carboxylato bridging ligands ( 1 h ) on BiVO 4 , an AM 1.5G photocurrent density of 5 mA cm −2 at 1.23 V vs. RHE for water oxidation was obtained, the highest photocurrent for undoped BiVO 4 photoanodes. A high solar‐energy conversion efficiency of 1.84 % was obtained for the integrated photoanode, a sixfold enhancement over that of unmodified BiVO 4 . These results and the high surface charge separation efficiency support the role of surface‐modified molecular catalysts in improving PEC performance and demonstrate the potential of molecule/semiconductor hybrids for efficient artificial photosynthesis.