Novel graphitic carbon nitride g-C9N10 as a promising platform to design efficient photocatalysts for dinitrogen reduction to ammonia: the first-principles investigation

Abstract

Photocatalysts play a vital role in the process of harnessing and converting solar energy into storable and valuable chemical fuels. As a polymeric semiconductor, graphitic carbon nitride g-C₃N₄ has been regarded as a next-generation photocatalyst due to its appealing band structure and excellent physicochemical stability. However, low electron conductivity and weak visible light absorption hinder its practical application. In this work, for the first time, we rationally designed a new graphitic carbon nitride, g-C₉N₁₀, based on a self-doping strategy by substituting the C₃N₃ ring for bridging the N atom in g-C₃N₄. g-C₉N₁₀ exhibits higher electron conductivity and longer wavelength absorption than those of g-C₃N₄, which make it a highly photoactive photocatalyst. Moreover, on the basis of “acceptance and donation” mechanism, single boron atom-decorated g-C₉N₁₀ (B@g-C₉N₁₀) can act as an efficient metal-free photocatalyst for nitrogen reduction reactions (NRRs) with high faradaic efficiency. Our results demonstrate that B@g-C₉N₁₀ can effectively activate and reduce N₂ to NH₃ with a low overpotential of 0.22 V, while the competitive hydrogen evolution reaction (HER) is efficiently suppressed. In addition, the photo-generated external potential is adequate to drive the NRR, endowing B@g-C₉N₁₀ with spontaneous NRR capability under visible/infrared light irradiation. This work may provide a new strategy for designing photocatalysts with high photoactivity and proposes g-C₉N₁₀ as a promising platform for designing efficient photocatalysts, which is expected to motivate more research efforts to explore.