Doping-engineered biphenylene as a metal-free electrocatalyst for the hydrogen evolution reaction

The rational design of metal-free electrocatalysts with excellent catalytic activity and high chemical stability is at the core of large-scale hydrogen production from water splitting. Herein, using first-principles calculations, we investigated the hydrogen evolution reaction (HER) electrocatalytic activity of X-doped (X = B, N, P, S) biphenylene (BPN). BPN was successfully synthesized experimentally and our results show that heteroatom doping can effectively enhance the electrocatalytic activity towards the HER. The beta-site P-doped BPN has an optimal Gibbs free energy for hydrogen (Delta G(H*)) value of 0.01 eV and excellent exchange current density (-1.48 A cm(-2)). In addition, we also revealed that the electrocatalytic activity is better when the heteroatom replaces a beta-site C atom instead of an alpha-site C atom. According to the results of the band structure of X-doped BPN, P atom doping can enhance the charge transfer from hydrogen to C atoms, corresponding to an appropriate p-band center. Furthermore, we demonstrated that P-doped BPN prefers the Volmer-Heyrovsky mechanism for the HER, and the reaction energy barrier is only 0.8 eV. Our work provides a strategy for designing a new metal-free HER electrocatalyst, which is predicted to be employed in HER catalysis with low cost and high performance.