Pressure dependence in aqueous-based electrochemical CO2 reduction

Abstract

Electrochemical CO2 reduction (CO2R) is an approach to closing the carbon cycle for chemical synthesis. To date, the field has focused on the electrolysis of ambient pressure CO2. However, industrial CO2 is pressurized—in capture, transport and storage—and is often in dissolved form. Here, we find that pressurization to 50 bar steers CO2R pathways toward formate, something seen across widely-employed CO2R catalysts. By developing operando methods compatible with high pressures, including quantitative operando Raman spectroscopy, we link the high formate selectivity to increased CO2 coverage on the cathode surface. The interplay of theory and experiments validates the mechanism, and guides us to functionalize the surface of a Cu cathode with a proton-resistant layer to further the pressure-mediated selectivity effect. This work illustrates the value of industrial CO2 sources as the starting feedstock for sustainable chemical synthesis.

Enabling Further Organic Electrolyte Infiltration of Cellulose-Based Separators via Defect-Rich Polypyrrole Modification for High Sodium Ion Transport in Sodium Metal Batteries

“…The peak due to the pyrrole β-position carbons is centered at 283.9 eV, while that of the α-position carbons is at 284.8 eV. 35,41,42 There is an energy separation of approximately 0.9 eV between the two peaks, consistent with the energy splitting observed in previous research. 41 Compared with the PPY-L@FIBER sample, the ratio of β-position carbons in PPY-H@FIBER increases and the ratio of α-position carbons decreases (Figure 3c), indicating that the interchain links and side chains appear more at the higher polymerization temperature.…”

“…The peaks at 398.3 and 399.6 eV represent the imine-like structure (−N�) and the pyrrole nitrogen (−NH−) structures, respectively. 42 The two peaks at higher binding energies (400.3 and 401.6 eV) represent polaron and bipolaron, respectively, 44 which are distributed along the doped PPY chain and serve as additional electron carriers. Each anionic doping on the PPY chain must be compensated for by a positively charged nitrogen atom (N + ) to maintain charge neutrality in the polymer.…”

“…In order to further confirm the concentration of imine-like structure and doping level of PPY, the high-resolution spectrum of N 1s (Figure b) can be deconvoluted into four different peaks located at 398.3, 399.6, 400.3, and 401.6 eV. The peaks at 398.3 and 399.6 eV represent the imine-like structure (–N) and the pyrrole nitrogen (–NH–) structures, respectively . The two peaks at higher binding energies (400.3 and 401.6 eV) represent polaron and bipolaron, respectively, which are distributed along the doped PPY chain and serve as additional electron carriers.…”

Influence of Environmental Conditions on Electrocatalytic CO2 Reduction

“…investigated the CO 2 RR process on Cu, Au, Ag, and Sn electrodes under high‐pressure conditions using Raman spectroscopy (Figure 8d), and found that formate selectivity was enhanced with increasing pressure (Figure 8e). [109] It was confirmed by operando Raman spectroscopy and density functional theory (DFT) calculations that the high formate selectivity was related to the increased CO 2 coverage on the cathode surface and that the increase in CO 2 coverage would further weaken the competing HER (Figure 8f). Appropriate adjustment of pressure can increase the reaction rate, improve product selectivity, and optimize the reaction conditions to some extent.…”

Designing and Engineering Atomically Dispersed Metal Catalysts for CO2 to CO Conversion: From Single to Dual Metal Sites

“…Depending on the practical reaction conditions, the electrolyte membrane, serving as a separator, can be either an anion exchange membrane (AEM) [129] or a proton exchange membrane (PEM). [130] Moreover, a bipolar membrane (BPM) is also used in a CO 2 electrolyzer to convert bicarbonate back to CO 2 and prevent CO 2 crossover. [121] Additionally, the GDLs sandwiched between the membrane-supported catalyst and the electrode boost prolonged contact between the electrocatalyst and CO 2 molecules during electrolyte flow, enhancing reaction rates compared to H-cell systems.…”