Incorporating Unique B-N Motifs into Graphene for Efficient Photocatalytic CO₂ Reduction

Abstract

Developing efficient metal-free photocatalysts for CO₂ reduction remains challenging due to the difficulty in simultaneously achieving suitable bandgaps, efficient charge separation, and strong visible-light absorption. Boron–nitrogen (B–N) doping offers a promising route to engineer graphene’s electronic structure, yet how B–N concentration and spatial configuration jointly govern photocatalytic properties remains poorly understood. Here, we systematically engineer graphene’s photocatalytic properties by incorporating B–N motifs with controlled density and spatial arrangement. Two optimal configurations, 66Gr-6BN and 66Gr-3BN2-7ring, are identified, exhibiting direct bandgaps of 1.75 eV and 2.10 eV, strong visible-light absorption, and exceptionally low exciton binding energies (< 0.5 eV), comparable to titanium dioxide (~0.2 eV), a benchmark metal-based photocatalyst, and substantially lower than graphitic carbon nitride (~3.0 eV), the most representative 2D metal-free photocatalyst. Their band edges span the redox potentials for CO₂ reduction to CO, CH₃OH, and CH₄, ensuring sufficient thermodynamic driving forces (up to 1.56 V) for multi-electron reduction pathways. Free energy analysis shows that overall reaction barriers remain below 0.8 eV under photoexcitation, suggesting feasibility under ambient conditions. This work provides promising catalyst candidates and establishes quantitative structure–property relationships that can guide the rational design of graphene-based metal-free photocatalysts.