Novel metal-free holey BC4N nanostructure for enhanced photoelectrocatalytic nitrogen reduction: insight from grand-canonical density functional theory

The carbon-based metal-free catalysts with graphene-like structures have been demonstrated to be highly efficient in promoting both photocatalytic and electrocatalytic reactions. Here, in the framework of constant potential model (CPM), we computationally explore material and catalytic properties of the proposed novel two-dimensional BC4N structure for promoting the photoelectrocatalytic (PEC) N2 reduction reaction (NRR). The results reveal that BC4N as a photocathode exhibits high efficiency of harvesting visible light and ultraviolet light. The photogenerated electrons can deliver a potential of Ue = −1.07 V, sufficient to overcome the potential-limiting step in PEC NRR in continuum aqueous electrolyte solution. Moreover, it is found that the co-adsorbed reaction intermediates play an important role in mediating/facilitating the NRR towards NH3 formation. Ab-initio molecular dynamics simulations indicate that the proton-coupled electron transfer can interplay with the intermolecular hydrogen transfer, leaving NRR mechanism even complicated at the atomic scale. The underlying disparity in CPM and the popular constant charge model was also discussed. This study provides fundamental insight into working mechanism of metal-free semiconducting materials driving photo-assisted PEC NRR under quasi-realistic conditions.