Activating photocatalytic hydrogen evolution by constructing Ni-based organic layers and tailoring its crystal facets

Abstract

The development of highly active and stable cheap cocatalysts is critical for the photocatalytic hydrogen evolution reaction (HER). Metal–organic frameworks have attracted much attention because of their high aspect ratio and well-defined coordination structures, but they are always catalytically inactive due to the sluggish reaction kinetics. In this work, two Ni metal–organic layers (MOLs), Ni-MOL-100 exposing rich (100) crystal facets and Ni-MOL-010 exposing (010) crystal facets were synthesized by tuning the molar ratios of metal ions and organic ligands. Compared with the bulk structure, the catalytic activities of the MOLs are activated for the HER. Impressively, Ni-MOL-100 showed 12 times higher activity than MOL-010. Experimental and theoretical calculation results demonstrate that the enhanced activity of Ni-MOL-100 is attributed to its appropriate conduction band potential to promote the photo-generating carrier transfer and more exposure of coordination-unsaturated Ni(II) ions sites with optimized hydrogen adsorption free energy to accelerate the hydrogen evolution reaction rate. This work demonstrates the important role of crystal surface tailoring engineering in the design of photocatalytic hydrogen evolution cocatalysts.