Graphitic carbon nitride supported Ni–Co dual-atom catalysts beyond Ni1(Co1) single-atom catalysts for hydrogen production: a density functional theory study

Using density functional theory calculations we investigate the formation, structure and electronic properties of gh-C₃N₄-supported Ni-Co (Ni-Co/gh-C₃N₄) dual-atom catalysts and Ni₁(Co₁) single-metal catalysts, as a paradigmatic example of single-atom versus few-atom catalysts. An inverted mold assumption is proposed to identify the factors determining the number, shape and packing manner of metal atoms inside the pores of gh-C₃N₄. The area matching between virtual fragments and metal fillers and lattice inheritance from N coordination and metal aggregates allow for a stable Ni-Co/gh-C₃N₄, which would possess more active sites and a more complex structure-activity relation than single-atom doping. The hydrogen production behavior and catalytic activity of this catalyst are comprehensively discussed. Ni-Co/gh-C₃N₄ exhibits higher hydrogen evolution activity than Ni₁(Co₁)/gh-C₃N₄ at an appropriate H coverage, which is comparable to Pt under analogous conditions. This strategy, derived from the inverted mold assumption, is deemed to be a simple and easy-to-operate method for designing and building metal aggregates confined inside the pores of two-dimensional materials and in the cavities of nanoparticles for few-atom catalysts.