MXenes and their derivatives as nitrogen reduction reaction catalysts: recent progress and perspectives

MXenes have become one of the most actively studied emerging materials. They hold a great promise as efficient catalysts for chemical conversion and environmental purification, due to their unique layered structures, high specific surface areas, abundant active sites, and excellent chemical stability. Recent breakthroughs demonstrate MXenes and their derivatives in adsorbing, activating, and converting nitrogen (N2) to ammonia (NH3) via electrocatalytic and photocatalytic nitrogen reduction reaction (NRR). The NRR is considered a green and environmentally friendly NH3 synthesis utilizing N2 and water molecules under mild conditions, unlike the current-day Haber-Bosch technology that directly uses fossil with intensive energy processes. However, the NH3 yield and efficiency of NRR using MXene-based catalysts remain too low to meet practical applications. Therefore, a fundamental understanding of NRR mechanisms and their significant challenges should be addressed for future development. In this review, we summarize a theoretical investigation of the promising properties of MXenes as NRR catalysts and discuss the recent development of MXenes and their derivatives in NRR and their enhancement strategies. The synthesis protocols to obtain tunable morphology, nanocomposite-based, and derivatives of MXenes are also presented. Furthermore, this review will provide new perspectives on future research to realize clean and sustainable NH3 production.