Highly Selective Solar CO2 Conversion into Formic Acid in Nickel-Perylene-C3N4 Semiconductor Photocatalyst

Abstract

Photocatalytic (PC) CO₂ reduction reaction (CO₂RR) into value-added oxygenated products is one of the most promising ways of solving climate warming change and energy crisis simultaneously. To reach higher selectivity and productivity of fuel products, it still remains great challenge in controlling both simultaneous sequential multi-electron/proton shuttling through different transporting pathway, which determines the intermediates and final products. Consequently, a multifunctional nickel-perylene-carbon nitride nanosheet (NS-P-g-C₃N₄-Ni) are constructed rationally to strengthen the electron and proton transfer via different pathway at the same time through molecule-level carbon backbone with excellent conductivity/charge capacity and proton transport via pendant functional group of -NH₂ from water oxidation sites of Ni metal cluster on perylene skeleton. CO₂ adsorption is enhanced and reduction energy is reduced by the complexation of N-atom site of NS-P-g-C₃N₄-Ni and adjustment of co-planarity, optimizing conduction band and band gap with energy controllable techniques. In situ FT-IR/Raman/EPR spectra identified and verified the transformation of active intermediates (^*CO₂^•−, ^*COOH and H^*COO⁻) adsorbed on the NS-P-g-C₃N₄-Ni by complexation and highly selective production of formic acid (60%) is achieved. This work sheds light on the construction of effective well-structured sites in photocatalytic CO₂ reduction to produce value-added products with higher selectivity and productivity.