MXenes for CO 2 Reduction and H 2 Generation

The issue of global warming and energy conservation has put enormous stress on the environment, demanding long-term sustainability of animal and plant life on our planet. Thus, it is important to develop strategies to produce hydrogen energy from water and control CO 2 emission by reducing them to valuable fuels or chemicals by using solar power. This has attracted intensive attention worldwide and researchers are investigating the development of alternative sources of environment-friendly, carbon-neutral, clean, and renewable energy. Two-dimensional (2D) materials like metal oxides, graphene, metal-organic frameworks, transition metal dichalcogenides (TMDs), and their heterostructures have been extensively used as potentially viable candidates for efficient H 2 production and conversion of CO 2 to fuels, owing to their fascinating electrical and thermal behavior, high specific surface area, outstanding mechanical and optical properties, and good chemical stability. This chapter summarizes the most recently developed 2D transition metal carbides and nitrides, called “MXenes.” These extraordinary 2D materials have outperformed other 2D materials in a wide variety of applications and have become more progressive in recent years in the development of high-performance electrocatalysts and photocatalysts for CO 2 reduction reaction (CO 2 RR) and hydrogen evolution reaction (HER). So far, more than 30 varieties of MXenes have been experimentally reported and used as catalysts, as they exhibit high catalytic activity, highly tunable optical and electronic functionalities due to the possibility of varied surface terminations, and mixed metal atoms in high entropy MXenes. MXenes as electro- and photocatalysts for CO 2 RR and HER applications have a great potential for commercialization and providing an economically viable solution for renewable and clean energy harvesting.