Molecular Co O cubane water oxidation catalysts were combined with BiVO 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 hybrid photoanodes to be tailored. Upon loading a new cubane complex featuring alkoxy carboxylato bridging ligands (1 h) on BiVO , an AM 1.5G photocurrent density of 5 mA cm at 1.23 V vs. RHE for water oxidation was obtained, the highest photocurrent for undoped BiVO photoanodes. A high solar-energy conversion efficiency of 1.84 % was obtained for the integrated photoanode, a sixfold enhancement over that of unmodified BiVO . 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.

A highly active supramolecular system for visible light-driven water oxidation was developed with cyclodextrin-modified ruthenium complex as the photosensitizer, phenyl-modified ruthenium complexes as the catalysts, and sodium persulfate as the sacrificial electron acceptor. The catalysts were found to form 1:1 host-guest adducts with the photosensitizer. Stopped-flow measurement revealed the host-guest interaction is essential to facilitate the electron transfer from catalyst to sensitizer. As a result, a remarkable quantum efficiency of 84% was determined under visible light irradiation in neutral aqueous phosphate buffer. This value is nearly 1 order of magnitude higher than that of noninteraction system, indicating that the noncovalent incorporation of sensitizer and catalyst is an appealing approach for efficient conversion of solar energy into fuels.

Cobalt–oxo cubane clusters were immobilized on a Nafion film-coated fluorine-doped tin oxide (FTO) electrode and an α-Fe2O3 photoanode as surface catalysts for water oxidation. The performance of electrochemical water splitting indicated that these earth-abundant metal complexes retain their homogeneous reactivity on the electrode. Furthermore, efficient visible light-driven water oxidation was realized by coupling a molecular electrocatalyst with an inorganic semiconductor as a noble metal-free photoanode, showing a stability significantly improved with respect to that of the homogeneous system.

The activity of eleven separated iron complexes and nine in situ-generated iron complexes towards catalytic water oxidation have been examined in aqueous solutions with Ce(NH4)2(NO3)6 as the oxidant. Two iron complexes bearing tridentate and tetradentate macrocyclic ligands were found to be novel water oxidation catalysts. The one with tetradentate ligand exhibited a promising activity with a turnover number of 65 for oxygen evolution.

Chromophore-catalyst molecular assemblies towards visible light-driven water oxidation were synthesized by covalent integration of a light-harvesting complex [Ru(bpy)3](2+) (bpy=2,2'-bipyridine) and a Co4O4 cubane water oxidation catalyst. The two components were assembled either in linear or macrocyclic configurations. In the presence of the sacrificial reagent, the Ru-Co metallocycle exhibits remarkable photocatalytic activity for oxygen evolution, which is one order of magnitude higher than that of a multicomponent system and exceeds that of a linear assembly by a factor of five, offering access to highly active photocatalyst through molecular design.