Electron deficient boron-doped amorphous carbon nitride to uphill N2 photo-fixation through π back donation

Abstract

The photocatalytic Nitrogen fixation to NH3 by using water as a protonation source is a requisite renovation for life. Albeit, the activation and adsorption of robust NN is the bottleneck in NH3 synthesis. Here, we report an amorphous-wrinkled hollow-tubular electron-deficient boron-doped carbon nitride (BCN) for improved photocatalytic N2 fixation via “σ donation and π back donation”. The electron-deficient B played synergetic roles to activate and stabilize the adsorbed N2 i.e. (i) It tunes the bandgap of CN for effective light absorption and charge transfer; (ii) The B-N coordination site polarizes chemisorbed N2 via electron pair acceptance; (iii) The filled sp2 orbital of B activates the N2 by π-back donation. Consequently, the photocatalytic performance of BCN-4 reaches 0.93mmolh−1g−1 with AQY of ∼13% (350 nm) and solar to NH3 conversion efficiency (SSCNH3) of 0.017%. The in situ DRIFT and DFT studies revealed that BCN exhibited spontaneous N2 adsorption and activation, followed by protonation of the adsorbed N2, with a negligible energy barrier.