Nitrogen cycle on N-doped graphene loaded TiO2 for efficient photocatalytic dinitrogen conversion

Abstract

Artificial nitrogenase through photocatalytic nitrogen fixation is known as the holy grail for the production of the valuable ammonia. Recently, the artificial nitrogenase is undergoing a revival for two main reasons including the prospect of substituting the obsolete Haber-Bosch method for producing ammonia, in combination with the simple setup for large scale applications. Notwithstanding much works have been done through surface modification of semiconductor, the actual scheme in nitrogenase can be hardly duplicated because the role of MoFe protein as electron mediator was often neglected.In this work, by integrating the rutile TiO2 with the N doped graphene (NG), the artificial nitrogenase system was successfully fabricated. In details, the TiO2 , graphene and N doping can respectively analogize the Fe protein for supplying photogenerated electrons, MoFe protein for manipulating the electron flow and MoFe-cofactor for providing binding and activation site for N2 . In such a system, the photogenerated charge carrier can be effectively utilized for overall dinitrogen conversion, reaching an ammonia production rate of 236.6 μg/h/gcat and a NO production rate of 242.5 μg/h/gcat . More importantly, the nitrogen cycle was proposed to explain why the NG could act as the electron mediator and N2 activation site during photocatalytic nitrogen fixation. Our work not only offers a viable way to duplicate the natural nitrogenase system, but also shine some light on the photocatalytic nitrogen fixation pathway on a N-containing photocatalytic system.