Influence of B-atom in g-C3N4 matrix to enhance the photocatalytic dinitrogen to ammonia conversion

Abstract

Boron-doped metal-free catalysts (B-g-C3N4) were successfully synthesized via the facile thermal polymerization method. In B-doped g-C3N4 synthesis, boric acid was varied viz; 1%, 3%, 6%, and 9% as compared to 2 g of melamine. 6% B-doped g-C3N4 was found to be the optimized catalyst showcasing enhanced performance for photocatalytic nitrogen reduction reaction (NRR). XRD and FT-IR results revealed that B doping did not change the basic chemical structure of g-C3N4. The presence of boron in the synthesized materials was confirmed via EDS, Elemental mapping, and XPS analysis. Boron doping also increased the carrier lifetime of g-C3N4 confirmed by time-resolved photoluminescence analysis. 6% B-g C3N4 showed the best photo-catalytic ammonia production among all the synthesized catalysts. It could produce ammonia up to 345.35 μmol.L−1.h−1 as compared to pure g-C3N4 (112.06 μmol. L −1.h −1). There was no loss of N2 reduction activities after 5 cycles of catalyst reuse. Mott-Schottky, photocurrent, and EIS were used to determine the flat band potential, electron recombination rate, and charge transfer resistance. Post N2 reduction, XRD, and XPS analysis of pure g-C3N4 and 6% B-g-C3N4 were almost identical revealing high stability of the doped g-C3N4. The doped boron enhances the optical and electrical properties and enhances photocatalytic activity for the production of NH3.