As a promising and important carbon source, utilization of carbon dioxide (CO2) can effectively solve the energy crisis caused by fossil resource consumption and the environmental problems arising from the emission of CO2.

The family of transition metal carbides, nitrides, and carbonitrides (collectively called MXenes) has been a thriving field since the first invention of Ti3C2Tx (MXene) in 2011. MXene is a new type of nanometer 2D sheet material, which exhibits great application potentials in various fields due to its multiple advantages such as high specific surface area, good electrical conductivity, and high mechanical strength. Electrocatalysis is regarded as the core of future clean energy conversion technologies, and MXene‐based materials provide inspiration for the design and preparation of electrocatalysts with high activity, high selectivity, and long loading life time. The applications of MXene‐based materials in electrocatalysis, including hydrogen evolution reaction, nitrogen reduction reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and methanol oxidation reaction are summarized in this review. As a crucial session regarding experiments, the current safer and more environmentally friendly preparation methods of MXene are also discussed. Focusing on the materials design and enhancement methods, the key challenges and opportunities for MXene‐based materials as a next‐generation platform in both fundamental research and practical electrocatalysis applications are presented. This account serves to promote future efforts toward the development of MXenes and related materials in the electrocatalysis applications.

chnology.S he received her bachelor's degree from Jining university,P .R. China. Her research focuses on the electrocatalytic NH 3 synthesis at ambient conditions. Dr.T ingli Ma received her Ph.D. degree in 1999 from Department of Chemistry,F aculty of Science of Kyushu University,J apan. She then joined the National Institute of Advanced Industrial Science and Te chnology (AIST,J apan) as aP ostdoctoral Researcher from 1999 to 2004. She worked as ap rofessor at the Dalian University of Te chnology from 2007-2018. She is working at the Graduate School of Life Science and Systems Engineering Kyushu Institute of Technology,J apan and China Jiliang University.S he leads research teams studying inorganic and organic solar cells, such as dye-sensitized and perovskite solar cells, and other related projects including development of catalysts, hydrogen production, functional dyes, and nano-sized semiconducting materials. Dr.M ah as published more than 200 papers in peer-reviewed journals. Figure 1. Schemeo fe lectrochemicalcell for NH 3 production by electrocatalytic NRR. [30] Published with permission. CopyrightE lsevier,2 018.

Compared with the traditional Haber–Bosch process, electrochemical ammonia synthesis has attracted much attention owing to its low energy consumption, low pollution potential, and sustainability.

A Co-based MOF supported on Ti3C2 MXene was prepared via in situ growth, which can efficiently reduce nitrogen to ammonia under environmental conditions.

Electrocatalytic nitrogen reduction reaction (NRR), as a potential alternative to industrial ammonia synthesis (Haber‐Bosch method), can achieve “green” and sustainable ammonia production under environmental conditions. However, the NRR process is still limited by the slow cleavage of the N≡N triple bond and the existence of a competitive hydrogen evolution reaction. For this reason, many researchers have studied the construction and synthesis of high‐efficiency nitrogen reduction electrocatalysts. Herein, a Co‐based metal‐organic framework (ZIF‐67) was used to prepare Co/C‐900 composites through high‐temperature pyrolysis (900 °C) for ammonia synthesis under environmental conditions. The Co/C‐900 catalysts exhibited excellent NRR performance, with a high NH3 yield of 4.66 μmol cm−2 h−1 at −0.3 V (vs. RHE) and a faradaic efficiency of 11.53 % in 0.1 M potassium hydroxide. This work provides a simple strategy for the design of porous, non‐noble‐metal electrocatalysts for electrochemical NRR.

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