The efficient storage of solar energy in chemical fuels, such as hydrogen, is essential for the large-scale utilisation of solar energy systems. Recent advances in the photocatalytic production of H2 are highlighted. Two general approaches for the photocatalytic hydrogen generation by homogeneous catalysts are considered: HX (X = Cl, Br) splitting involving both proton reduction and halide oxidationvia an inner-sphere mechanism with a single-component catalyst; and sensitized H2 production, employing sacrificial electron donors to regenerate the active catalyst. Future directions and challenges in photocatalytic H2 generation are enumerated.
