2D-2D MnO₂/g-C₃N₄ heterojunction photocatalyst: In-situ synthesis and enhanced CO₂ reduction activity

A novel MnO₂/g-C₃N₄ heterojunction composite was synthesized via a simple in-situ redox reaction between KMnO₄ and MnSO₄·H₂O adsorbed on the surface of g-C₃N₄ for the first time. MnO₂ featuring 2D δ-phase layered structure was intimately attached onto the surface of g-C₃N₄ layers via [sbnd]C[sbnd]O[sbnd] bonding. Notably, the synthesized MnO₂/g-C₃N₄ photocatalyst showed substantially enhanced photocatalytic activity in the reduction of CO₂ than pure g-C₃N₄ and MnO₂. The highest CO production amount of 9.6 μmol g⁻¹ has been obtained at an optimized loading amount of MnO₂ under 1 h irradiation of a 300 W Xe lamp. The incorporation of narrow band gap MnO₂ on the surface of g-C₃N₄ enhanced its light harvesting ability. And the solid hetero-interface between MnO₂ and g-C₃N₄ together with their well matched band structure was favorable for the separation of photo-induced carriers, consequently enhanced its photocatalytic activity. This novel 2D-2D MnO₂/g-C₃N₄ heterostructure is expected to have great potentials in CO₂ photoreduction.