Direct low concentration CO₂ electroreduction to multicarbon products via rate-determining step tuning.

Abstract

Direct converting low concentration CO₂ in industrial exhaust gases to high-value multi-carbon products via renewable-energy-powered electrochemical catalysis provides a sustainable strategy for CO₂ utilization with minimized CO₂ separation and purification capital and energy cost. Nonetheless, the electrocatalytic conversion of dilute CO₂ into value-added chemicals (C₂₊ products, e.g., ethylene) is frequently impeded by low CO₂ conversion rate and weak carbon intermediates' surface adsorption strength. Here, we fabricate a range of Cu catalysts comprising fine-tuned Cu(111)/Cu₂O(111) interface boundary density crystal structures aimed at optimizing rate-determining step and decreasing the thermodynamic barriers of intermediates' adsorption. Utilizing interface boundary engineering, we attain a Faradaic efficiency of (51.9 ± 2.8) % and a partial current density of (34.5 ± 6.4) mA·cm^-2 for C₂₊ products at a dilute CO₂ feed condition (5% CO₂ v/v), comparing to the state-of-art low concentration CO₂ electrolysis. In contrast to the prevailing belief that the CO₂ activation step ( <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>C</mi> <mi>O</mi></mrow> <mrow><mn>2</mn></mrow> </msub> <mo>+</mo> <msup><mrow><mi>e</mi></mrow> <mrow><mo>-</mo></mrow> </msup> <mo>+</mo> <mspace></mspace> <mo>*</mo> <mspace></mspace> <mo>→</mo> <mmultiscripts><mrow><mi>C</mi> <mi>O</mi></mrow> <mrow><mn>2</mn></mrow> <mrow><mo>-</mo></mrow> <mprescripts></mprescripts> <none></none> <mrow><mo>*</mo></mrow> </mmultiscripts> </math> ) governs the reaction rate, we discover that, under dilute CO₂ feed conditions, the rate-determining step shifts to the generation of *COOH ( <math xmlns="http://www.w3.org/1998/Math/MathML"> <mmultiscripts><mrow><mi>C</mi> <mi>O</mi></mrow> <mrow><mn>2</mn></mrow> <mrow><mo>-</mo></mrow> <mprescripts></mprescripts> <none></none> <mrow><mo>*</mo></mrow> </mmultiscripts> <mo>+</mo> <msub><mrow><mi>H</mi></mrow> <mrow><mn>2</mn></mrow> </msub> <mi>O</mi> <mo>→</mo> <mmultiscripts><mi>C</mi> <none></none> <none></none> <mprescripts></mprescripts> <none></none> <mrow><mo>*</mo></mrow> </mmultiscripts> <mi>O</mi> <mi>O</mi> <mi>H</mi> <mo>+</mo> <msup><mrow><mi>O</mi> <mi>H</mi></mrow> <mrow><mo>-</mo></mrow> </msup> <mrow><mo>(</mo> <mrow><mi>a</mi> <mi>q</mi></mrow> <mo>)</mo></mrow> </math> ) at the Cu⁰/Cu¹⁺ interface boundary, resulting in a better C₂₊ production performance.