Understanding trends in the activity and selectivity of bi-atom catalysts for the electrochemical reduction of carbon dioxide†

Electrocatalytic CO2 reduction offers a promising approach to produce valuable chemicals using greenhouse gas as the feedstock, although the reduction efficiency on conventional transition metal catalysts is limited by the inherent scaling relations. How to break this scaling relation becomes crucial for improving the catalytic efficiency. Recent experiments have witnessed great advances in precisely controlling the synthesis of bi-atom catalysts (BACs), which contributes to their unique catalytic properties being different from single-atom catalysts (SACs) and nanoparticles. However, atomic-level insights into the structure-properties relationship of BACs have become a great challenge. Herein, we develop a fundamental understanding of the trends in the catalytic activity of homo- and hetero-nuclear BACs via large-scale DFT calculations. We demonstrate that homonuclear BACs still follow the scaling relations. By constructing heteronuclear BACs from metal groups with strong COOH* adsorption (Ti, V, Cr, Mn, Mo, and Ta) and weak CO* adsorption (Fe, Co, Ni, Cu, Zn, Ga, Rh, and Ir), the linear relationships could significantly be broken, caused by the different O- and C-affinity of the heterocenters that work synergistically to affect the adsorption of CO2 and COOH*/HCOO*. The adsorption of *CO, however, cannot be easily tuned due to its single coordination mode. In terms of the reaction selectivity, the primary product with homonuclear BACs was CO or HCOOH, while the heteronuclear BACs mainly produce CO or H-2. Our analysis shows an efficient design feature to modulate the adsorption of COOH* (HCOO*) without regulating CO*, which provides useful insight into the design of efficient multi-active-site CO2RR electrocatalysts.

Automated summary

Electrocatalytic CO2 reduction is a promising approach for producing valuable chemicals using greenhouse gases, but breaking the traditional scaling relations on conventional transition metal catalysts is crucial to improving efficiency. Recent advances in precise control over the synthesis of biatom catalysts have shown unique catalytic properties different from single-atom catalysts and nanoparticles. While homonuclear BACs still follow scaling relations, heteronuclear BACs can significantly break linear relationships by utilizing different O and C affinities of the heterocenters.