Revisiting the Impact of Morphology and Oxidation State of Cu on CO<sub>2</sub> Reduction Using Electrochemical Flow Cell
Abdullah M. Asiri, Jing Gao, Sher Bahadar Khan, Khalid A. Alamry, Hadi M. Marwani, Mohammad Sherjeel Javed Khan, Waheed A. Adeosun, Shaik M. Zakeeruddin, Dan Ren, Michaël Grätzel
Abstract
Electroreduction of carbon dioxide (CO2) in a flow electrolyzer represents a promising carbon-neutral technology with efficient production of valuable chemicals. In this work, the catalytic performance of polycrystalline copper (Cu), Cu2O-derived copper (O(I)D-Cu), and CuO-derived copper (O(II)D-Cu) toward CO2 reduction is unraveled in a custom-designed flow cell. A peak Faradaic efficiency of >70% and a production rate of ca. −250 mA cm–2 toward C2+ products have been achieved on all the catalysts. In contrast to previous studies that reported a propensity for C2+ products on OD-Cu in conventional H-cells, the selectivity and activity of ethylene-dominated C2+ products are quite similar on the three types of catalysts at the same current density in our flow reactor. Our analysis also reveals current density to be a critical factor determining the C–C coupling in a flow cell, regardless of Cu catalyst’s initial oxidation state and morphology.