Sequential catalysis enables enhanced C-C coupling towards multi-carbon alkenes and alcohols in carbon dioxide reduction: a study on bifunctional Cu/Au electrocatalysts

• Published in: Faraday discussions 2019-07, Vol.215, p.282-296
• Main Authors: Gao, Jing, Ren, Dan, Guo, Xueyi, Zakeeruddin, Shaik Mohammed, Grätzel, Michael
• Format: Article
• Language: English
• Subjects: Alcohols; Alkenes; Bimetals; Carbon dioxide; Carbon monoxide; Catalysis; Catalysts; Chemical reduction; Copper compounds; Copper oxides; Electrocatalysts; Energy storage; Ethanol; Ethylene; Exchanging; Gold; Gold compounds; Hydrogen evolution; Intermetallic compounds; Nanoparticles; Nanowires
• ISSN: 1359-6640; 1364-5498
• DOI: 10.1039/c8fd00219c

Electrochemical reduction of carbon dioxide (CO 2 ) to multi-carbon products such as ethylene, ethanol and n -propanol offers a promising path for utilization of excessive CO 2 and energy storage. Oxide-derived Cu electrodes are among the best electrocatalysts for the selective formation of ethylene and ethanol. However, a large fraction of the faradaic current still goes to hydrogen evolution, even at optimal conditions (electrolyte, potential, etc. ). Here we employ the concept of sequential catalysis using judiciously designed CuAu bimetallic catalysts through galvanic exchange between Au 3+ and Cu 2 O nanowires. By controlling the concentration of the Au 3+ precursor and the exchange time, Au nanoparticles were evenly dispersed onto the Cu 2 O nanowires. The optimized oxide-derived CuAu catalyst showed remarkable improvement towards the formation of ethylene, ethanol and n -propanol, in terms of faradaic efficiency and current density. Our analysis of the electrochemical formation of carbon monoxide, ethylene and hydrogen suggests that the presence of Au, an electrocatalyst for CO 2 -to-CO conversion, helps enhance *CO-coverage on Cu, thus promoting the production of multi-carbon products and suppressing hydrogen formation on the CuAu catalyst. We propose promising strategies for designing electrochemical systems, which would enable the selective and scalable reduction of CO 2 to ethylene and ethanol. We employed the concept of sequential catalysis to design CuAu bifunctional catalysts for the selective and scalable reduction of CO 2 to ethylene and ethanol.