Hydrophobic Electrode Design for CO 2 Electroreduction in a Microchannel Reactor.

Microchannel reactor is a novel electrochemical device to intensify CO 2 mass transfer with large interfacial areas. However, if the catalyst inserted in the microchannel is wetted, CO 2 is required to diffuse across the liquid film to get access to reaction sites. In this paper, a hydrophobic polytetrafluoroethylene (PTFE)-doped Ag nanocatalyst on a Zn rod was synthesized through a facile galvanic replacement of 2Ag + +Zn → 2Ag + Zn 2+ . The catalyst layer, which was PTFE incorporated into the Ag matrix, was detected to distribute uniformly on the Zn substrate with a thickness of 77 μm. Consequently, the PTFE-doped electrode demonstrated enhanced activity with an optimal 96.19% CO faradaic efficiency (FE CO ) in the microchannel reactor. Typically, the catalyst could maintain over 90% FE CO even at the current density of 24 mA cm -2 , which was nearly 30% higher than that of a similar catalyst without PTFE. In addition, influences of the concentration of PTFE and deposition time were also investigated, determining that 1 vol % of PTFE and 30 min of coating yielded best electrocatalytic efficiency. To achieve a further breakthrough of CO 2 mass transfer limitations, reactions were applied under relatively high pressures (3-15 bar) in a single-compartment high-pressure cell. The maximum CO partial current density ( j CO ) can reach 106.76 mA cm -2 at 9 bar.