Hole scavenger-free nitrogen photofixation in pure water with non-metal B-doped carbon nitride: Implicative importance of B species for N2 activation
Jiale Lee, Steven Hao Wan Kok, Boon‐Junn Ng, Xin Ying Kong, Lutfi Kurnianditia Putri, Siang‐Piao Chai, Lling‐Lling Tan
Abstract
Being the energy glutton and top ranker of greenhouse gas emission, Haber-Bosch is undoubtedly a grand challenge to reaching sustainability and carbon neutrality. Solar-driven nitrogen (N2) fixation under mild conditions is highly attractive and promising for sustainable ammonia (NH3) production. However, low conversion efficiency remains as a serious problem yet to be solved due to the difficult activation of strongly non-polar NN bond. In this study, defective and atomically thin g-C3N4 with boron sites was synthesized via a facile decomposition-thermal polymerization technique. The optimum photocatalyst displayed an NH3 yield of 213.59 μmol gcat−1 h−1 under visible light irradiation (λ > 400 nm) without any hole scavenger, bestowing high suitability for N2 fixation in pure water. The impressive performance is largely ascribed to the introduction of B species, which could act as the active sites for N2 adsorption, activation and reduction. Additionally, the atomically thin layer (∼3.25 nm) shortens charge carrier transport pathway while the B atoms and defects suppress quantum size effect as well as extends photo-response through bandgap reduction. These attributes synergistically lead to suppressed electron-hole recombination, efficacious charge transport, enhanced light utilization and enriched catalytic sites for N2 fixation. As a whole, this work presents an easy strategy to realize efficient N2 photofixation over a metal-free, low-cost and non-toxic photocatalyst in pure water as a continuous effort in advancing the burgeoning field of photocatalytic N2 fixation.