Insight into photocatalytic nitrogen fixation on graphitic carbon nitride: Defect-dopant strategy of nitrogen defect and boron dopant

[Display omitted] •A defect-dopant strategy is proposed to boost photocatalytic nitrogen fixation.•Nitrogen defects and B atoms dopant enhance the chemisorption of N2.•Longer N–N bond length is favorable for activating robust NN triple bonds.•Excellent charge behaviors induce enhanced molecular oxygen activation ability. Designing efficient semiconductors for photocatalytic nitrogen reduction reaction (N2RR) is an urgent challenge for artificial ammonia (NH3) production under ambient condition. Graphitic carbon nitride (GCN) shows fascinating potential in conversion of inert chemical bonds into high-value-added products. However, the low NH3 conversion efficiency in GCN leads to unsatisfied practical application. Herein, a defect-dopant strategy through introduction of nitrogen defects and boron (B) heteroatoms is proposed to boost NH3 production. The optimal catalyst shows enhanced photocatalytic activity with NH3 conversion rate of 435.28 μmol g−1 h−1 under visible light illumination. The boosting NH3 production is owing to the synergistic effect of nitrogen defect and B dopant. The nitrogen defect is favorable for promoting the optical harvesting ability, charge carrier separation efficiency as well as N2 adsorption ability. B dopant not only enhances N2 adsorption and activation ability, but also maintains the high reduction ability of BNUCNx. Density functional theory (DFT) calculation shows that high adsorption energy for N2 and longer N–N bond length of N2 are simultaneously obtained in BNUCNx, contributing to NH3 production. Furthermore, the high molecular oxygen activation ability in BNUCNx shows great potential for environmental remediation. This work provides a pioneering perspective for enhancing photocatalytic N2RR through defect-dopant strategy.