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Summary: Nitrogen oxides (NOx) emissions carry pernicious consequences on air quality and human health, prompting an upsurge of interest in eliminating them from the atmosphere. The electrochemical NOx reduction reaction (NOxRR) is among the promising techniques for NOx removal and potential conversion into valuable chemical feedstock with high conversion efficiency while benefiting energy conservation. However, developing efficient and stable electrocatalysts for NOxRR remains an arduous challenge. This review provides a comprehensive survey of recent advancements in NOxRR, encompassing the underlying fundamentals of the reaction mechanism and rationale behind the design of electrocatalysts using computational modeling and experimental efforts. The potential utilization of NOxRR in a Zn-NOx battery is also explored as a proof of concept for concurrent NOx abatement, NH3 synthesis, and decarbonizing energy generation. Despite significant strides in this domain, several hurdles still need to be resolved in developing efficient and long-lasting electrocatalysts for NOx reduction. These possible means are necessary to augment the catalytic activity and electrocatalyst selectivity and surmount the challenges of catalyst deactivation and corrosion. Furthermore, sustained research and development of NOxRR could offer a promising solution to the urgent issue of NOx pollution, culminating in a cleaner and healthier environment.

The unique properties of MXenes have been deemed to be of significant interest in various emerging applications. However, MXenes provide a major drawback involving environmentally harmful and toxic substances for its general fabrication in large-scale production and employing a high-temperature solid-state reaction followed by selective etching. Meanwhile, how MXenes are synthesized is essential in directing their end uses. Therefore, making strategic approaches to synthesize greener, safer, more sustainable, and more environmentally friendly MXenes is imperative to commercialize at a competitive price. With increasing reports of green synthesis that promote advanced technologies and non-toxic agents, it is critical to compile, summarize, and synthesize the latest development of the green-related technology of MXenes. We review the recent progress of greener, safer, and more sustainable MXene synthesis with a focus on the fundamental synthetic process, the mechanism, and the general advantages, and the emphasis on the MXene properties inherited from such green synthesis techniques. The emerging use of the so-called green MXenes in energy conversion and storage, environmental remediation, and biomedical applications is presented. Finally, the remaining challenges and prospects of greener MXene synthesis are discussed.