Identification of single-atom-anchored g-CN as pH universal photo- and electro- catalysts for hydrogen evolution

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Identifying efficient and low-cost catalysts for electrocatalytic and photocatalytic hydrogen evolution reaction (HER) is critical for renewable energies, yet it remains an immense challenge. Through density functional theory calculations, we systematically investigate the great potential of 30 single-atom catalysts (SACs), namely single-atom-anchored g-CN (M/g-CN), toward electrocatalytic and photocatalytic HER in all pH intervals. Through Gibbs free energy (ΔGH*) calculations, electrical conductivity as well as water dissociation kinetic analysis, six M/g-CN (M = Sc, Ti, V, Ga, Sn, Au) are identified as pH universal electrocatalysts for HER. After excluding the influence of charge and solvation on ΔGH*, M/g-CN (M = V, Ga, Sn, Au) can still be regarded as potential pH universal electrocatalysts for HER. In addition, by combination of band structures with ΔGH* assessments, five M/g-CN (M = Ti, Ni, Ru, Pd, Os) are expected to be pH universal photocatalysts for HER. In particular, Ti/g-CN and Pd/g-CN possess favorable solar light harvesting and proton reducing kinetics, which can be regarded as the essential photo-electro integrated catalysts for HER. Moreover, employing machine learning method, the activity origin for HER on SACs is unveiled, and it is demonstrated that the charge transfer plays the decisive impact accompanied by the synergy effect from a series of structural characteristics. This work gives a new approach to design and search potential HER catalysts.