Direct carbon fuel cell (DCFC) is a promising technology with high energy efficiency and abundant fuel. To date, a variety of DCFC configurations have been investigated, with molten hydroxide, molten carbonate or oxides being used as the electrolyte. Recently, there has been particular interest in DCFC with molten carbonate involved. The molten carbonate is either an electrolyte or a catalyst in different cell structures. In this review, we consider carbonate as the clue to discuss the function of carbonate in DCFCs, and start the paper by outlining the developments in terms of molten carbonate (MC)-based DCFC and its electrochemical oxidation processes. Thereafter, the composite electrolyte merging solid carbonate and mixed ionic–electronic conductors (MIEC) are discussed. Hybrid DCFC (HDCFCs ) combining molten carbonate and solid oxide fuel cell (SOFC) are also touched on. The primary function of carbonate (i.e., facilitating ion transfer and expanding the triple-phase boundaries) in these systems, is then discussed in detail. Finally, some issues are identified and a future outlook outlined, including a corrosion attack of cell components, reactions using inorganic salt from fuel ash, and wetting with carbon fuels.

直接碳燃料电池（DCFC）是一种具有高能效和丰富燃料的有前途的技术。迄今为止，已经研究了各种 DCFC 配置，使用熔融氢氧化物、熔融碳酸盐或氧化物作为电解质。最近，人们对涉及熔融碳酸盐的 DCFC 特别感兴趣。熔融碳酸盐在不同的电池结构中要么是电解质，要么是催化剂。在这篇综述中，我们将碳酸盐作为讨论碳酸盐在 DCFC 中的功能的线索，并通过概述基于熔融碳酸盐 (MC) 的 DCFC 及其电化学氧化过程的发展来开始本文。此后，讨论了融合固体碳酸盐和混合离子电子导体（MIEC）的复合电解质。还涉及结合熔融碳酸盐和固体氧化物燃料电池 (SOFC) 的混合 DCFC (HDCFC)。然后详细讨论碳酸盐在这些系统中的主要功能（即促进离子转移和扩大三相边界）。最后，确定了一些问题并概述了未来前景，包括电池组件的腐蚀攻击、使用来自燃料灰的无机盐的反应以及碳燃料的润湿。