Manipulating the Morphology and Electronic State of a Two-Dimensional Coordination Polymer as a Hydrogen Evolution Cocatalyst Enhances Photocatalytic Overall Water Splitting

Abstract

To achieve efficacious photocatalytic overall water splitting, surface modification of photocatalysts with proficient cocatalysts for hydrogen evolution reaction (HER) is imperative. NiBHT, a conductive two-dimensional coordination polymer (2D CP), or a 2D metal–organic framework (2D MOF), endowed with remarkable chemical stability and HER selectivity, emerged as a promising candidate for an HER cocatalyst. However, the bulky morphology of NiBHT hampered its performance. Here, we demonstrate a strategy to miniaturize NiBHT by incorporating the benzene-1,2-dithiol (BDT) ligand, yielding NiBHT nanoparticles (NiBHT-NP). Beyond morphology, empirical evidence unveiled alterations in the electronic state and catalytic activity of NiBHT-NP, and the ramifications of BDT modulation on intrinsic characteristics are elucidated through density functional theory (DFT) calculations. As a model system, CoOx/SrTiO3:Al photocatalyst with NiBHT-NP modification exhibited an apparent quantum efficiency (AQE) of 10.3% at 365 nm for overall water splitting. This pioneering work showcases that a modulator ligand may manipulate the morphology, electronic state, and catalytic behavior of 2D CPs, holding prodigious potential for developing more effective CP-based HER cocatalysts.