Facet- and structure-dependent catalytic activity of cuprous oxide/polypyrrole particles towards the efficient reduction of carbon dioxide to methanol

Abstract

The preparation of cost-effective, stable catalysts for the selective reduction of carbon dioxide (CO2) to C1 products such as methanol is extremely important because methanol can be used directly as a fuel or it can be converted into other value-added products. However, the catalysts currently used for the reduction of CO2 to methanol exhibit poor selectivity, poor stability and very low faradaic efficiency. Herein, we used low-cost, stable cuprous oxide/polypyrrole (Cu2O/Ppy) particles having structures of octahedra and icosahedra (microflowers) that were prepared on linen texture (LT) papers for the selective reduction of CO2 to form a value-added single C1 product, methanol. The Cu2O/Ppy particles possessing both octahedral and microflower shapes with exposed low-index (111) facets and high-index (311) and (211) facets are denoted as Cu2O(OL-MH)/Ppy particles. The as-prepared Cu2O(OL-MH)/Ppy particles exhibited high catalytic activity and selectivity towards the electrochemical reduction of CO2 at -0.85 V vs. RHE to form methanol, with a faradaic efficiency of 93 ± 1.2% and an average methanol formation rate of 1.61 ± 0.02 μmol m-2 s-1. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the pyrrolic nitrogen atoms present in the Ppy shell played a dominant role as active sites for CO2 molecules. The Raman bands of Ppy and Cu2O did not shift even after being subjected to electrolysis for several hours, suggesting superior stability of the Cu2O(OL-MH)/Ppy particles. The high resolution microscopic, spectroscopic, diffraction and electrochemical analysis results clearly revealed that the Ppy shell protected the Cu2O particles and avoided corrosion, dissolution, and structural and crystal facet changes, leading to greater stability. The low-cost, durable, flexible, and catalytically active Cu2O(OL-MH)/Ppy LT paper holds great potential for catalytic, photocatalytic and energy storage applications.

Sustainable Membrane‐Coated Electrodes for CO2 Electroreduction to Methanol in Alkaline Media

“…[48] After Ru-based CCM [53] Gas phase 0.46 0.90 0.93 CuÀ TiO 2 /NG based GDE [54] Near neutral (pH = 6.8) À 0.20 À 0.06 19.5 Cu-doped CNTs based GDE [55] Alkaline (pH = 9) 0.28 À 4.75 47.4 CuÀ Bi MOFs based GDE [15] Near neutral (pH = 6.8) blend solution causing densification of the membrane overlayer upon casting and solvent evaporation, as well as the largest water transport reported elsewhere. [47] The diffusion layer thickness can be estimated using the Nernst diffusion layer Equation (2), [56] As Cu in other polymer-coated electrodes studied in the state of Cu(II), [48] their efficiency towards CO 2 conversion was enhanced by the polymer coating.…”

“…Thus, assuming that CO 2 RR in alkaline media generates bicarbonate anions as Equation (12) 4 and CH 3 OH on a Cu catalyst. [11] Periasamy et al proposed a similar route for MeOH production, [47] by [Eqs. Then, an aldehyde was generated after another pair e À þH þ transferred.…”

“…[58] Conductive polypyrrole could also increase the stability of Cu 2 O NPs in the CO 2 RR to methanol. [47] The diffusion layer thickness can be estimated using the Nernst diffusion layer Equation (2),…”

“…[19] AAEMs work by facilitating the flow of anions (e. g. OH À ) from the cathode to the anode. [47] With these new MCE structures, new reaction pathways and mechanisms may be possible, and the product selectivity can be tuned up by applying a transport-mediated reaction selectivity and the protective layers controlling the mass and ion transport to the metal electrocatalyst, by anticipating that rapid transport to the electrode and through a thin membrane and analyte preconcentration in the membrane improve the sensitivity of the system. [19] Thus the anion transport mechanism is expected to be more limiting for CO 2 RR with systems using AAEMs than CEMs because the forward reaction of CO 2 to products is encouraged without delivering H + to the cathode.…”

“…As an example, polypyrrole (Ppy) coating has been recently observed to increase the stability, conductivity, and catalytic activity of Cu 2 O shape structures on paper electrodes in CO 2 RR in aqueous electrolyte medium. [47] With these new MCE structures, new reaction pathways and mechanisms may be possible, and the product selectivity can be tuned up by applying a transport-mediated reaction selectivity and the protective layers controlling the mass and ion transport to the metal electrocatalyst, by anticipating that rapid transport to the electrode and through a thin membrane and analyte preconcentration in the membrane improve the sensitivity of the system. [38] Likewise, we believe that the dispersion of metal particles into a conductive polymeric matrix may provide synergies with the specific areas of metal catalyst and thus improve the catalytic efficiency.…”