Construction of a wide-spectrum-driven VN-g-C3N4/Cu2(OH)2CO3 heterojunction catalyst from VIS to NIR light via the in situ self-sacrificial method: the effect of oxygen on the N2 photofixation ability

Abstract

In this work, an N vacancy-doped g-C₃N₄/Cu₂(OH)₂CO₃ (V_N-GCN/CuCOH) heterojunction catalyst with superior wide-spectrum-driven (from VIS to NIR) N₂ photofixation ability was synthesized via the in situ self-sacrificial method. The characterization results show that the charge transfer between g-C₃N₄ and Cu₂(OH)₂CO₃ follows the “Z-scheme” mechanism. The addition of oxygen has a significant effect on the nitrogen photofixation performance of the as-prepared catalyst using methanol as a hole scavenger. Under the atmosphere of 50% O₂ and 50% N₂, the as-prepared V_N-GCN/CuCOH heterojunction catalyst displays an ammonium ion production rate as high as 14 mg L⁻¹ h⁻¹ g_cat⁻¹, which is 2.5 times higher than that under a pure nitrogen atmosphere. A “two-path” ammonia production mechanism is proposed in this work.