Since the discovery of N-doped carbon nanotubes as the first carbon-based metal-free electrocatalyst (C-MFEC) for oxygen reduction reaction (ORR) in 2009, C-MFECs have shown multifunctional electrocatalytic activities for many reactions beyond ORR, such as oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO₂RR), nitrogen reduction reaction (NRR), and hydrogen peroxide production reaction (H₂O₂PR). Consequently, C-MFECs have attracted a great deal of interest for various applications, including metal–air batteries, water splitting devices, regenerative fuel cells, solar cells, fuel and chemical production, water purification, to mention a few. By altering the electronic configuration and/or modulating their spin angular momentum, both heteroatom(s) doping and structural defects (e.g., atomic vacancy, edge) have been demonstrated to create catalytic active sites in the skeleton of graphitic carbon materials. Although certain C-MFECs have been made to be comparable to or even better than their counterparts based on noble metals, transition metals and/or their hybrids, further research and development are necessary in order to translate C-MFECs for practical applications. In this article, we present a timely and comprehensive, but critical, review on recent advancements in the field of C-MFECs within the past five years or so by discussing various types of electrocatalytic reactions catalyzed by C-MFECs. An emphasis is given to potential applications of C-MFECs for energy conversion and storage. The structure–property relationship for and mechanistic understanding of C-MFECs will also be discussed, along with the current challenges and future perspectives.

中文翻译：

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碳基无金属电催化剂：从氧还原到多功能电催化

自 2009 年发现 N 掺杂的碳纳米管作为第一个用于氧还原反应 (ORR) 的碳基无金属电催化剂 (C-MFEC) 以来，C-MFECs 已对 ORR 以外的许多反应显示出多功能电催化活性，例如析氧反应 (OER)、析氢反应 (HER)、二氧化碳还原反应 (CO ₂ RR)、氮还原反应 (NRR) 和过氧化氢生成反应 (H ₂ O ₂公关）。因此，C-MFECs 在各种应用中引起了极大的兴趣，包括金属-空气电池、水分解装置、再生燃料电池、太阳能电池、燃料和化学品生产、水净化等。通过改变电子配置和/或调节它们的自旋角动量，杂原子掺杂和结构缺陷（例如、原子空位、边缘）已被证明可以在石墨碳材料的骨架中产生催化活性位点。尽管某些 C-MFEC 已被制成与基于贵金属、过渡金属和/或它们的混合物的对应物相当甚至更好，但为了将 C-MFEC 转化为实际应用，还需要进一步的研究和开发。在本文中，我们通过讨论由 C-MFECs 催化的各种类型的电催化反应，对过去五年左右 C-MFECs 领域的最新进展进行了及时、全面但至关重要的回顾。重点介绍了 C-MFEC 在能量转换和存储方面的潜在应用。还将讨论 C-MFEC 的结构-性能关系和机理理解，