Theoretical Insights into the Hydrogen Evolution Reaction on VGeN and NbGeN Monolayers.

Catalytically active sites at the basal plane of two-dimensional monolayers for hydrogen evolution reaction (HER) are important for the mass production of hydrogen. The structural, electronic, and catalytic properties of two-dimensional VGeN and NbGeN monolayers are demonstrated using the first-principles calculations. The dynamical stability is confirmed through phonon calculations, followed by computation of the electronic structure employing the hybrid functional HSE06 and PBE+. Here, we introduced two strategies, strain and doping, to tune their catalytic properties toward HER. Our results show that the HER activity of VGeN and NbGeN monolayers are sensitive to the applied strain. A 3% tensile strain results in the adsorption Gibbs free energy (Δ ) of hydrogen for the NbGeN monolayer of 0.015 eV, indicating better activity than Pt (-0.09 eV). At the compressive strain of 3%, the Δ value is -0.09 eV for the VGeN monolayer, which is comparable to that of Pt. The exchange current density for the P doping at the N site of the NbGeN monolayer makes it a promising electrocatalyst for HER (Δ = 0.11 eV). Our findings imply the great potential of the VGeN and NbGeN monolayers as electrocatalysts for HER activity.