Manganese compounds as water oxidizing catalysts for hydrogen production via water splitting: From manganese complexes to nano-sized manganese oxides

For hydrogen production by water splitting, the water oxidation half reaction is overwhelmingly rate limiting and needs high over-voltage (∼1 V), which results in low conversion efficiencies when working at current densities required. At this high voltage, other chemicals will be also oxidized and this would be environmentally unacceptable for large-scale H2 production. t few years, there has been a tremendous surge in research on the synthesis of various metal compounds aimed at the simulating water oxidizing complex of Photosystem II. Particular attention has been given to the manganese compounds not only because manganese has been used by Nature to oxidize water but also because manganese is cheap and environmentally friendly. In this review, we focus on manganese compounds as functional models of the water oxidizing complex of Photosystem II for hydrogen production via water splitting.