Steering the Reaction Pathway of CO₂ Electroreduction by Tuning the Coordination Number of Copper Catalysts

Abstract

Cu-based catalysts are optimal for the electroreduction of CO₂ to generate hydrocarbon products. However, controlling product distribution remains a challenging topic. The theoretical investigations have revealed that the coordination number (CN) of Cu considerably influences the adsorption energy of *CO intermediates, thereby affecting the reaction pathway. Cu catalysts with different CNs were fabricated by reducing CuO precursors via cyclic voltammetry (Cyc-Cu), potentiostatic electrolysis (Pot-Cu), and pulsed electrolysis (Pul-Cu), respectively. High-CN Cu catalysts predominantly generate C₂₊ products, while low-CN Cu favors CH₄ production. For instance, over the high-CN Pot-Cu, C₂₊ is the main product, with the Faradaic efficiency (FE) reaching 82.5% and a partial current density (<i>j</i>) of 514.3 mA cm^-2. Conversely, the low-CN Pul(3)-Cu favors the production of CH₄, achieving the highest FE_CH4 value of 56.7% with a <i>j</i>_CH4 value of 234.4 mA cm^-2. In situ X-ray absorption spectroscopy and Raman spectroscopy studies further confirm the different *CO adsorptions over Cu catalysts with different CN, thereby directing the reaction pathway of the CO₂RR.