Two-Dimensional Metal-Organic Framework Acts as a HydrogenEvolution Cocatalyst for Overall Photocatalytic Water Splitting

Water-splitting semiconductor photocatalysts requirehydrogen evolution reaction (HER) cocatalysts, the majority of whichare robust metals and metal oxides. Metal complexes feature designabilityand reaction selectivity. This feature should be appreciated in theapplication as HER cocatalysts by suppressing unfavorable back reactions;however, low stability hampers their application. In this research, wedemonstrate that a fully pi-conjugated and conductive two-dimensionalmetal-organic framework (2D MOF), which possesses both virtues ofmetals/metal oxides and metal complexes, serves as an ideal HERcocatalyst candidate. NiBHT, a kind of 2D MOF, is deposited on thephotocatalyst SrTiO3:Al with CoOxas an oxygen evolution cocatalyst toshow long-term overall one-step water splitting with an apparent quantumefficiency (AQE) of 6.5% at 350 nm. In comparison to Pt as arepresentative HER cocatalyst, NiBHT turns out to be a suppressor of back reactions related to oxygen reduction reactions, which isproven both experimentally and theoretically.

Automated summary

This study demonstrates that a fully pi-conjugated and conductive two-dimensional metal-organic framework (2D MOF) serves as an ideal candidate for hydrogen evolution reaction (HER) cocatalyst, with low stability and suppressing back reactions related to oxygen reduction reactions.