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 discover that pressurization up to 50 bar steers CO2R pathways toward formate, as universally exemplified on common CO2R catalysts. By developing operando methods compatible with high pressures, including quantitative operando Raman spectroscopy, we ascribe the pronounced formate selectivity to the higher CO2* coverages and lower hydronium ion concentrations 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 hydronium-repelling 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.…”

Electrocatalytic upcycling of high-pressure captured CO2

“…This observation unveiled the inadequate CO 2 influx to the cathode-membrane interface, and implied that CO 2 consumption mainly occurred upon entry into the cathode, in good agreement with the substantially accumulated salt on the back side of the cathodic GDL under ambient pressure. As the pressure increased, the peak intensity of CO 3 2− diminished, whereas new peaks emerged at 1025 and 1285 cm −1 , which can be respectively assigned to the COH vibration of HCO 3 − and the stretching vibration of gas-phase CO 2 20,42 . When the pressure reached 10 bar and onward, the cathode-membrane interface was dominated by HCO 3 − and CO 2 , while CO 3 2− was barely detectable -that means, an abundance of CO 2 arrives at the cathode-membrane interface, where it depletes OH − to form bicarbonate and impedes the deprotonation of bicarbonate into carbonate (Fig.…”

“…Also under ambient pressure, converting amine-CO 2 adduct into CO was realized by regulating the electrochemical double layer with alkali cations 4 . Recently, studies under elevated pressure have shed light on the role of pressure in improving the selectivity of single CO 2 R products, primarily formate or acetate, in aqueous electrolyte-based H-shape cells [20][21][22] . These reports underscore the viability of electrochemically utilizing captured CO 2 , albeit in dissolved form.…”