Effect of pressure and temperature on carbon dioxide reduction at a plasmonically active silver cathode

Abstract

Carbon dioxide reduction at a plasmonically active silver cathode was investigated by varying the pressure and temperature at multiple applied potentials under both dark and illuminated conditions to understand the mechanism of selectivity changes driven by plasmon-enhanced electrochemical conversion. Carbon dioxide partial pressures (P CO2 ) from 0.2 to 1 atm were studied during linear sweep voltammetry and chronoamperometry at -0.7, -0.9, and -1.1 V RHE . At a given applied overpotential the total current density increased with increasing P CO2 in both the dark and the light, but there were significant differences in the Tafel behavior between dark and illuminated conditions. The reduction of CO 2 to carbon monoxide (CO) was found to have first-order behavior with respect to P CO2 at all applied potentials in both the dark and the light, likely indicating no change in the rate-determining step upon illumination. Activity for the hydrogen (H 2 ) evolution reaction decreased with increasing P CO2 at slightly different rates in the dark and the light at each applied potential, making it unclear if light is influencing CO or H 2 intermediate adsorbate coverage. Both formate and methanol production showed no dependence on P CO2 under any conditions, but the true reaction orders may be masked by the much higher activity for CO and H 2 at the silver cathode. The investigation of product distribution with temperature at 14, 22, and 32°C at -0.7, -0.9, and -1.1 V RHE in both the dark and the light demonstrated that the selectivity changes observed upon illumination are not caused by local heating of the cathode surface.

Surface plasmon assisted photoelectrochemical carbon dioxide reduction: progress and perspectives

“…As for the intricate plasmonic and thermal photoelectrochemical CO 2 RR, temperature and partial pressures of CO 2 across a range of applied potentials were comprehensively studied for CO 2 RR on a plasmonic Ag cathode. 124 This in-depth investigation showed that plasmon and thermal-enhanced electrochemical conversion could modulate an exact selectivity product. As the light enhanced CO and suppressed H 2 at −0.7 V vs. RHE, formate production was maximized at −0.9 V vs. RHE in light.…”

Alloying strategies for tuning product selectivity during electrochemical CO2reduction over Cu

“…[18][19][20][21] Additionally, other factors, such as temperature and pH (more critically local pH, since it can differ substantially from the bulk value, especially under high current density/low buffer capacity conditions) also influence the product selectivity during the eCO 2 RR. [22][23][24] Table 1 provides several examples of eCO 2 RR products generated in aqueous media and their reversible potentials (E°′) vs. the reversible hydrogen electrode (RHE). Significant drawbacks of eCO 2 RR in aqueous solutions are the low solubility of CO 2 resulting in low current densities, the presence of a competitive hydrogen evolution reaction (HER) which suppresses the overall eCO 2 RR efficiency, in addition to sluggish kinetics and hence a large overpotential required to produce commercially desirable products at a sufficient rate.…”

“…18–21 Additionally, other factors, such as temperature and pH (more critically local pH, since it can differ substantially from the bulk value, especially under high current density/low buffer capacity conditions) also influence the product selectivity during the eCO 2 RR. 22–24 Table 1 provides several examples of eCO 2 RR products generated in aqueous media and their reversible potentials ( E °′) vs . the reversible hydrogen electrode (RHE).…”

Applying Plasmonic Catalyst in CO2 Electrolyzer for Enhancing Energy Efficiency

“…A photocurrent density of −0.34 mA cm –2 was obtained upon light irradiation producing CO with 70% of Faradaic efficiency (FE) . It was suggested that light irradiation might assist CO desorption from the catalyst surface by the electrons excited from LSPR relaxation. , …”

“…32 catalyst surface by the electrons excited from LSPR relaxation. 33,34 We previously reported a photoassisted electrochemical (PAEC) CO 2 reduction system. 35 A three-electrode flow cell with GDE was fabricated as a cathode with a plasmonic catalyst of Au nanoparticles (Au NPs) deposited on Ag nanowires (Au NWs).…”