Selectivity and Durability in the Electrochemical Reduction of CO2 to C2 Products Using Cu-P, Cu-Sn and Cu-Se Electrocatalysts

Abstract

Ethylene is typically reported as the primary product from CO2 reduction at copper electrocatalysts in MEA-type cell configurations with alkaline anolytes. In this work, we evaluate CO2 reduction selectivity at Cu-P, Cu-Sn, and Cu2Se electrocatalysts that were synthesized via a common one-pot approach. Electron microscopy, X-ray diffraction and inductively coupled plasma optical emission spectrometry show 100-110 nm nanoparticles with uniform distributions of P, Sn, or Se. When using neutral (0.1 M KHCO3) anolytes, electrocatalysts with P-doping yield increases in ethylene Faradaic efficiency (up to 52 % at 150 mA cm-2) while Cu-Sn and Cu-Se electrocatalysts result in increased oxygenate selectivity. Cu-Sn electrocatalysts yield an FE of 24 % ethanol at 150 mAcm-2 and Cu2Se electrocatalysts yield an FE of 32 % to acetate at 150 mAcm-2. More alkaline anolytes (1 M KOH) further increased oxygenate formation, with 48 % ethanol Faradaic efficiency on Cu-Sn and 40 % acetate Faradaic efficiency on Cu2Se at 350 mA cm-2. Galvanostatic experiments were conducted at 150 mA cm-2 in 0.1 M KHCO3 electrolyte for over 200 h for the three electrocatalysts. Figure 1 shows the slow losses in FEs to C2 products (0.02 % per h) and increasing cell potentials (1 mV per h). In this talk, we consider the mechanisms for selectivity and the nature of durability improvements. Figure 1