Editorial for Advanced Energy Materials, Special Issue on Electrocatalytic and Photocatalytic N2 Fixation

Atmospheric nitrogen (N2), an accessible and abundant component of the air, serves as the primary nitrogen source for industrial ammonia synthesis and other nitrogen-related chemicals. Typically, the harsh activation conditions required for N2 fixation in industrial processes hinder the development of one-step synthesis processes and conflict with the goal of global carbon neutrality. Novel and mild electrocatalysis and photocatalysis offer promising pathways for the one-step conversion of inert N2 into nitrogen-related chemicals without significant energy consumption or environmental pollution. This special issue, organized and edited by Profs. Tierui Zhang, Shuangying Wang, and Yan Jiao, focuses on electrocatalytic and photocatalytic N2 fixation. It features 14 contributions (5 reviews and 9 research articles) authored by researchers from leading global institutions, including Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences, University of Chinese Academy of Sciences, Hunan University, University of Macau, King Abdullah University of Science and Technology, Georgia Institute of Technology, University of Adelaide, Tsinghua University, South China University of Technology, University of New South Wales, University of Sydney, City University of Hong Kong, Shenzhen University, Ulsan National Institute of Science and Technology, University of Colorado Boulder, Fuzhou University, and the University of Electronic Science and Technology of China. The issue encompasses a deep understanding of research areas, addressing many of the current hot topics in electrocatalytic and photocatalytic N2 fixation. Several original research articles discuss enhanced nitrogen activation or ammonia synthesis through novel catalyst design. Prof. Jalili et al. propose a liquid metal-based method for the synthesis of bismuth nano-electrocatalysts with controllable nanostructures (article number 2304287). In addition, Prof. Wang and co-workers design Al3+-protected black phosphorene as an electrocatalyst for the electrocatalytic reduction of nitrogen to ammonia (article number 2303963). Meanwhile, a photo-assisted ammonia synthesis system featuring a CeO2-supported Ru single-atom catalyst has been developed by Prof. Zhang's group (article number 2303792). Moreover, Prof. Liu and co-workers reported an atomically dispersed cobalt-phosphorus catalytic pair for activating nitrate, together with the promotion of water dissociation to release hydrogen protons for high-performance ammonia synthesis (article number 2400065). Other atomically scattered active centers that could accelerate the photocatalytic evolution of ammonia, such as Ru, Fe, Au, Pt, Cu, Mo, and La, have been also summarized by Prof. Qiao and his coworkers (article number 2400650). Also, Prof. Kim et al. overview the progress in single/multi atoms and 2D-nanomaterials for electro/photocatalytic nitrogen reduction from the aspects of experimental, computational, and machine learning developments (article number 2304106). Besides, Prof. Musgrave and co-workers investigate the binary covalent alloy space in theory for overcoming the limitations of nitrogen reduction reaction imposed by scaling relations in the adsorption of N-related species to improve nitrogen activation (article number 2304559). In theory, effective supply and utilization of protons is a prerequisite for highly productive ammonia synthesis. Accordingly, Prof. Jiao and co-workers reveal the scaling relation in proton utilization between nitrogen reduction reaction and hydrogen evolution reaction through DFT computations (article number 2303809). Experimentally, a bipolar membrane-based membrane electrode assembly system was designed to regulate the proton flux during operation by Prof. Hatzell's group, with the aim of promoting effective proton utilization (article number 2304202). Additionally, Prof. Wang et al. provide new insights into C─N coupling systems between CO2 and various nitrogen species, as well as the resulting C─N coupling products, e.g., amines, amides, amino acids, oximes, imines, and nitriles, especially urea (article number 2303820). Prof. Dong and co-workers realize an efficient solar-driven upgrading of N2 to urea through photoredox reactions on Pt Cluster/TiO2 (article number 2303806). Additionally, the fundamentals and rational design of heterogeneous C─N coupling electrocatalysts for urea synthesis at ambient conditions have been also offered by Prof. Lv and his co-workers (article number 2303588). Besides, Prof. Dai and co-workers give an in-depth review of the electrosynthesis of valuable organic nitrogen compounds at ambient conditions from the aforementioned earth-abundant resources/wastes by electrochemical C─N bond formation reactions, especially using carbon-based catalysts (article number 2401341). Meanwhile, reliable and precise product detection protocols suitable to photo/electrocatalytic N2 fixation or artificial photosynthesis of value-added aqueous chemicals have been established by Prof. Zhang and his co-workers for benefiting the healthy development of photo/electrocatalytic C─N coupling systems (article number 2303885). This special issue not only highlights recent progress and key challenges in photo/electrocatalytic N2 fixation to ammonia but also explores the innovative production of C─N coupling products such as urea. The critical perspectives presented in the reviews and some research articles underscore the future development directions for N2 fixation in electrocatalytic and photocatalytic synthesis. We are honored to serve as the guest editors of this special issue. The excellent contribution and great support from the authors, referees, and the Advanced Energy Materials editorial team are sincerely appreciated. The authors declare no conflict of interest. Tierui Zhang is a full professor at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. He obtained his Ph.D. degree in chemistry in 2003 at Jilin University. Subsequently he worked as a postdoctoral researcher in the labs of Prof. Markus Antonietti, Prof. Charl F. J. Faul, Prof. Hicham Fenniri, Prof. Z. Ryan Tian, Prof. Yadong Yin, and Prof. Yushan Yan. His current scientific interests focus on the catalytic nanomaterials for energy conversion. Shuangyin Wang is currently a professor of Joint International Research Laboratory of Energy Electrochemistry and the College of Chemistry and Chemical Engineering, Hunan University. He received his B.S. degree in 2006 from Zhejiang University and his Ph.D. degree in 2010 from Nanyang Technological University, Singapore. His research interests are focused on electrocatalysis and electrosynthesis. Yan Jiao obtained her Ph.D. in chemical engineering from the University of Queensland in 2012. Since graduation, she has been working at the University of Adelaide's School of Chemical Engineering. Her passion is to co-create a more sustainable world through her expertise in molecular modelling and interdisciplinary collaboration. Her expertise lies in the use of computational techniques for the design of clean and sustainable energy conversion materials.