Electrochemical CO₂ reduction to obtain formate or formic acid is receiving significant attention as a method to combat the global warming crisis. Significant efforts have been devoted to the advancement of CO₂ reduction techniques over the past few decades. This Account provides a unified discussion on various electrochemical methodologies for CO₂ to formate conversion, with a particular focus on recent advancements in utilizing 3d-transition-metal-based molecular catalysts. This Account primarily focuses on understanding molecular functions and mechanisms under homogeneous conditions, which is essential for assessing the optimized reaction conditions for molecular catalysts. The unique architectural features of the formate dehydrogenase (FDH) enzyme provide insight into the key role of the surrounding protein scaffold in modulating the active site dynamics for stabilizing the key metal-bound CO₂ intermediate. Additionally, the protein moiety also triggers a facile proton relay around the active site to drive electrocatalytic CO₂ reduction forward. The fine-tuning of FDH machinery also ensures that the electrocatalytic CO₂ reduction leads to the production of formic acid as the major yield without any other carbonaceous products, while limiting the competitive hydrogen evolution reaction. These lessons from the enzymes are key in designing biomimetic molecular catalysts, primarily based on multidentate ligand scaffolds containing peripheral proton relays. The subtle modifications of the ligand framework ensure the favored production of formic acid following electrocatalytic CO₂ reduction in the solution phase. Next, the molecular catalysts are required to be mounted on robust electroactive surfaces to develop their corresponding heterogeneous versions. The surface-immobilization provides an edge to the molecular electrocatalysts as their reactivity can be scaled up with improved durability for long-term electrocatalysis. Despite challenges in developing high-performance, selective catalysts for the CO₂ to formic acid transformation, significant progress is being made with the tactical use of graphene and carbon nanotube-based materials. To date, the majority of the research activity stops here, as the development of an operational CO₂ to formic acid converting electrolyzer prototype still remains in its infancy. To elaborate on the potential future steps, this Account covers the design, scaling parameters, and existing challenges of assembling large-scale electrolyzers. A short glimpse at the utilization of electrolyzers for industrial-scale CO₂ reduction is also provided here. The proper evaluation of the surface-immobilized electrocatalysts assembled in an electrolyzer is a key step for gauging their potential for practical viability. Here, the key electrochemical parameters and their expected values for industrial-scale electrolyzers have been discussed. Finally, the techno-economic aspects of the electrolyzer setup are summarized, completing the journey from tactical design of molecular catalysts to their appropriate application in a commercially viable electrolyzer setup for CO₂ to formate electroreduction. Thus, this Account portrays the complete story of the evolution of a molecular catalyst to its sustainable application in CO₂ utilization.

中文翻译：

---

CO2 到甲酸的电催化转化：从 3D 过渡金属基分子催化剂设计到电解槽组装的旅程


电化学还原 CO₂ 以获得甲酸盐或甲酸作为应对全球变暖危机的一种方法受到广泛关注。在过去的几十年里，人们为推动 CO₂ 减排技术的发展付出了巨大的努力。本帐户对 CO₂ 到甲酸盐转化的各种电化学方法进行了统一讨论，特别关注利用基于 3D 过渡金属的分子催化剂的最新进展。本科目主要侧重于了解均相条件下的分子功能和机理，这对于评估分子催化剂的优化反应条件至关重要。甲酸盐脱氢酶 （FDH） 酶的独特结构特征有助于深入了解周围蛋白质支架在调节活性位点动力学以稳定关键金属结合的 CO₂ 中间体中的关键作用。此外，蛋白质部分还触发活性位点周围的简单质子中继，以向前驱动电催化 CO₂ 还原。FDH 机械的微调还确保电催化 CO₂ 还原导致甲酸的产生作为主要产量，而无需任何其他碳质产品，同时限制了竞争性的析氢反应。这些从酶中得到的经验教训是设计仿生分子催化剂的关键，主要基于包含外周质子中继的多齿配体支架。配体框架的细微修饰确保了在溶液相中电催化 CO₂ 还原后有利于甲酸的产生。 接下来，需要将分子催化剂安装在坚固的电活性表面上，以开发其相应的非均相版本。表面固定化为分子电催化剂提供了优势，因为它们的反应性可以提高，并且具有更高的耐久性，可实现长期电催化。尽管在开发用于 CO₂ 到甲酸转化的高性能选择性催化剂方面存在挑战，但在战术性使用石墨烯和碳纳米管基材料方面正在取得重大进展。迄今为止，大部分研究活动都止步于此，因为可操作的 CO₂ 转化为甲酸电解槽原型的开发仍处于起步阶段。为了详细说明未来可能的步骤，本帐户涵盖了组装大型电解槽的设计、缩放参数和现有挑战。这里还简要介绍了电解槽在工业规模减少 CO₂ 方面的应用。正确评估组装在电解槽中的表面固定化电催化剂是衡量其实际可行性潜力的关键步骤。本文讨论了工业规模电解槽的关键电化学参数及其预期值。最后，总结了电解槽装置的技术经济方面，完成了从分子催化剂的战术设计到它们在 CO₂ 到甲酸盐电还原的商业上可行的电解槽装置中的适当应用的旅程。因此，本报道描绘了分子催化剂演变到其在 CO₂ 利用中的可持续应用的完整故事。