Enhanced Performance of Molecular Electrocatalysts for CO₂ Reduction by Cations

Electrocatalytic carbon dioxide (CO₂) reduction using water is the key to artificial photosynthesis systems designed to produce fuels. The performance of the electrochemical CO₂ reduction reaction has improved dramatically in recent years, with current densities of 1 A/cm² or higher being achieved using gas diffusion electrodes. On the other hand, high voltages are used to achieve high current densities, which leads to the problem of extremely low efficiency in converting electrical energy into chemical energy. In addition, high voltages are required in PV-EC systems combined with solar cells, and expensive GaAs-based space solar cells are needed. The catalysts used in these reaction systems are mainly noble metals such as Au and Ag, and there are few reported cases of complex catalysts. This is because complex catalysts, while stable in H-type cells immersed in solution, are not as durable as metal catalysts when used in gas diffusion electrodes, as they are deactivated within a few hours.[1]<br/>We have succeeded in using the effect of carbon and alkali metal cations to drive a Mn complex, which is not normally driven as a catalyst, as a CO₂ reduction catalyst even in an aqueous solution.[2] We have shown that this effect is also effective for other complex catalysts, and we consider it essential for the CO₂ reduction reaction. Here, we focus on the reaction environment around the catalyst at the gas diffusion electrode. There are no alkali metal cations around the catalyst. Therefore, in order to improve the CO₂ reduction performance, we investigated the possibility of introducing alkali metal cations such as K⁺ into the carbon layer of the gas diffusion electrode. As a result, we have successfully developed a new Co complex catalyst electrode for reducing CO₂ to CO with high selectivity (&gt;95%), high energy efficiency (~70%), and high durability (&gt;1 week) at 100 mA/cm². [3] In this presentation, we will discuss the details of researching the new electrocatalytic system using cations effects in carbon layer.<br/><br/>References:<br/>[1] S. Ren et al., Science 365, 367 (2019). [2] S. Sato et al., ACS Catal. 8, 4452 (2018).<br/>[3] S. Sato et al., Sci. Adv. 9, eadh9986 (2023).