The state-of-the-art developments in the photocatalytic reduction of N2 to NH3 are presented by classifying the photocatalysts based on chemical composition. Additionally, the correlation between the modification of catalysts and their photocatalytic activity is highlighted.

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In 2011, a new and growing family of two-dimensional (2D) transition-metal carbides, nitrides, and carbonitrides (MXenes) was discovered. Benefitting from intriguing electronic and structural properties, MXenes have received increasing attention and emerged as next-generation nanomaterials for the exploration of environmentally friendly energy resources for catalysis in energy and environmental technologies. In this review, we systematically highlight the expeditious advances and achievements in design strategies, physico-chemical properties, and catalytic applications of 2D layered MXenes and their nanocomposites in environmental science and renewable energy. In addition, we unravel the structural, optical, and electronic properties of MXenes to elucidate their key roles of ameliorating the niche areas of photo(electro)catalytic hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, carabon dioxide reduction reaction, nitrogen reduction reaction, and pollutant degradation. This review concludes with invigorating perspectives, outlooks, and formidable challenges in the future development of MXene-based materials for sustainable applications.

Two-dimensional (2D) transition-metal (groups IV, V, VI) carbides (MXenes) with formulas MC have been investigated as CO conversion catalysts with well-resolved density functional theory calculations. While MXenes from the group IV to VI series have demonstrated an active behavior for the capture of CO, the CrC and MoC MXenes exhibit the most promising CO to CH selective conversion capabilities. Our results predicted the formation of OCHO and HOCO radical species in the early hydrogenation steps through spontaneous reactions. This provides atomic level insights into the computer-aided screening for high-performance catalysts and the understanding of electrochemical mechanisms for CO reduction to energy-rich hydrocarbon fuels, which is of fundamental significance to elucidate the elementary steps for CO fixation.

Black phosphorus, which is a relatively rare allotrope of phosphorus, was first discovered by Bridgman in 1914. Since the advent of two-dimensional (2D) black phosphorus (which is known as phosphorene due to its resembling graphene sheets) in early 2014, research interest in the arena of black phosphorus was reignited in the scientific and technological communities. Henceforth, a myriad of research studies on this new member of the 2D world have been extensively emerged. Fascinatingly, 2D black phosphorus exhibits a distinctive wrinkled structure with the high hole mobility up to 1000 cm2 V−1 s−1, excellent mechanical properties, tunable band structures, anisotropic thermal, electrical and optical properties, thus leading to its marvelous prospects in device applications. This review firstly introduces the state-of-the-art development, structural properties and preparation routes of black phosphorus. In particular, anisotropy involved in mechanical properties, thermal conductivity, carrier transport as well as optical properties is comprehensively discussed. Apart from discussing the recent progress in black phosphorus which is applied to devices (i.e. field effect transistors and optoelectronic), the review also highlights the bottlenecks encountered by the society and finally casts an invigorating perspective and insightful outlook on the future direction of the next-generation 2D black phosphorus by harnessing its remarkable characteristics for energy production.