Visible light driven efficient metal free single atom catalyst supported on nanoporous carbon nitride for nitrogen fixation

Abstract

The production of ammonia (NH₃), an important carbon-free chemical, through nitrogen (N₂) fixation under mild conditions, is one of the most challenging and attractive chemical processes for industrial applications. However, most N₂ fixation occurs through transition-metal based systems and examples of metal-free catalysts remain elusive. Herein, by means of first-principles computations, we demonstrate that dynamical as well as highly thermally stable (up to 800 K) single boron atom doped nanoporous carbon nitride materials, i.e. C₂N monolayers, are a potential metal-free single atom catalyst for efficient N₂ fixation under visible light absorption. Based on the B–N synergistic effect, N₂ strongly binds to the B/C₂N surface through end-on and side-on modes respectively. Our computation reveals that the single B atom doped C₂N-concept catalyst could effectively reduce N₂ to NH₃ with a record low onset potential (0.18 eV) through enzymatic pathways and can sufficiently suppress the competing hydrogen evolution reactions. Multimodal binding of gas phase N₂ molecules with selective stabilization of N_xH_x by proton–electron (H⁺ + e⁻) pairs leads to the highest catalytic performance of B/C₂N. Moreover, deposition of single B atoms on C₂N dramatically enhances the absorption of light in the visible and IR regions, rendering it a promising solar light-driven N₂ to NH₃ reduction (NRR) catalyst. The excellent formation energy of B doped C₂N advocates its experimental synthesis.