Electrosynthesis of formic acid/formate, a valuable feedstock widely used in industrial processes, through electrocatalytic CO₂ reduction reaction (CO₂RR), is a promising alternative protocol to industrially ways. However, the development of high-efficiency electrocatalysts is challenging. When considering the CO₂ overall splitting process, the kinetically sluggish and energy-intensive oxygen evolution reaction in anode could drag down the whole electrochemical efficiency. 

In a study published in Adv. Mater., the research group led by Prof. ZHU Qilong from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences reported a facile pair-electrosynthesis tactic for exclusively producing formate via coupling selectively electrocatalytic methanol oxidation reaction (MOR) and CO₂RR, achieving concurrent yielding of formate at both anode and cathode with greatly reduced energy input. 

In the MOR-participated CO₂ overall splitting system, the researchers designed and prepared the self-supported Ni- Metal-organic-framework (MOF)-derived nanosheet arrays (Ni-NF-Af) and a series of Bi-MOF-derived bismuthenes through an in situ electrochemical conversion process as efficient anodic and cathodic electrocatalysts, respectively. 

They found that the as-prepared Ni-NF-Af used as the MOR electrocatalyst only needs low potentials of 1.345 and 1.388 V to deliver the industrial-scale current densities of 100 and 500 mA cm^-2 for methanol-to-formate conversion with ~100% selectivity, respectively, much superior over most of the reported Ni-based electrocatalysts. 

The as-prepared Bi-enes used as the CO₂RR electrocatalyst can simultaneously exhibit high selectivity (> 95%), large partial current density (70 mA cm^–2) and quite good stability in a potential window exceeding 0.4 V toward formate production. 

The MOR-participated CO₂ overall splitting system based on these distinctive MOF-derived catalysts not only can reduce the energy input exceeding 0.21 V, but also deliver high current densities and nearly 100% selectivity for formate production in both anode and cathode. 

This study opens up a new way to design high-performance MOF-derived 2D electrocatalysts, and also provides a new sight into the development of more high-efficiency CO₂ overall splitting system and electrosynthesis system for electrochemical production of valuable feedstocks. 

A pair-electrosynthesis tactic for concurrent formate production in electrocatalytic CO₂ overall splitting system via in situ MOF-derived 2D electrocatalysts. (Image by Prof. ZHU’s group)