Solar-driven water splitting

Abstract

Investigators in our NSF CCI Solar Fuels Program are working on catalysts for both water oxidn. to dioxygen (OER) and proton redn. to dihydrogen (HER). Promising HER heterogeneous catalysts include Ni-Mo and CoP, which reduce protons in aq. solns. with catalytic efficiencies near that of platinum. We also are investigating sol. iron, cobalt, and nickel complexes that catalyze dihydrogen prodn. from protic solns. at relatively low overpotentials. Employing laser flash/quench and NMR methods, we have shown that the active intermediate in cobalt-catalyzed dihydrogen evolution is a Co(II)-hydride. Among several new photoanode materials synthesized at Caltech, one that is esp. promising is dinitrogen-intercalated tungsten oxide. This 1.9 eV band gap oxide exhibits photocurrent under illumination out to 640 nm with a faradaic efficiency near unity for OER in perchloric acid solns. In other work of note, we have shown that robust metal-oxide water oxidn. catalysts can be made by pulsed laser ablation of precursors in liqs.

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