Proton Shuttling by Polyaniline of High Brønsted Basicity for Improved Electrocatalytic Ethylene Production from CO₂

Abstract

Hybrid organic/inorganic composites with the organic phase tailored to modulatelocal chemical environment at the Cu surface arise as an enchanting category of catalysts for electrocatalytic CO2 reduction reaction (CO2RR). A fundamental understanding on how the organics of different functionality, polarity, and hydrophobicity affect the reaction path is, however, still lacking to guide rational catalyst design. Herein, polypyrrole (PPy) and polyaniline (PANI) manifesting different Brønsted basicity are compared for their regulatory roles on the CO2RR pathways regarding *CO coverage, proton source and interfacial polarity. Concerted efforts from in situ IR, Raman and operando modelling unveil that at the PPy/Cu interface with limited *CO coverage, hydridic *H produced by the Volmer step favors the carbon hydrogenation of *CO to form *CHO through a Tafel process; Whereas at the PANI/Cu interface with concentrated CO2 and high *CO coverage, protonic H+ shuttled through the benzenoid −NH− protonates the oxygen of *CO, yielding *COH for asymmetric coupling with nearby *CO to form *OCCOH under favored energetics. As a result of the tailored chemical environment, the restructured PANI/Cu composite demonstrates a high partial current density of 0.41 A cm‐2 at a maximal Faraday efficiency of 67.5% for ethylene production, ranking among states of the art.

Cu–phen Coordination Enabled Selective Electrocatalytic Reduction of CO2 to Methane

“…The higher coverage of *CO adsorbents and coupling between the *CO atop and *CO bridge intermediates was proposed to be favorable for C 2+ products . Furthermore, the existence of both the *COCO intermediate (1560 cm –1 ) and *COCHO (1410, 1342 cm –1 ) indicated that *COCHO formation was likely to proceed via *COCO hydrogenation, which was commonly established as a key intermediate in the C 2 pathway. , Besides, the peak at 1218 cm –1 , ascribed to the adsorbed *OCCOH species, became prominent, which was generated by asymmetric coupling of *COH with neighboring *CO and recognized as a crucial intermediate for the generation of C 2 H 4 …”

“…40 Furthermore, the existence of both the *COCO intermediate (1560 cm −1 ) 41 and *COCHO (1410, 1342 cm −1 ) indicated that *COCHO formation was likely to proceed via *COCO hydrogenation, which was commonly established as a key intermediate in the C 2 pathway. 42,43 Besides, the peak at 1218 cm −1 , ascribed to the adsorbed *OCCOH species, became prominent, which was generated by asymmetric coupling of *COH with neighboring *CO 44 and recognized as a crucial intermediate for the generation of C 2 H 4 . 45 Furthermore, in situ Raman spectroscopy was also employed in a spectro-electrochemical flow cell, to probe into the evolution of the Cu-based catalysts during the eCO 2 RR process at different applied potentials (−0.5 to −2.0 V vs RHE) in 1 M KOH electrolyte (Figure S14, Supporting Information).…”

Tunable-pH Environment Induced by Local Anchor Effect of High Lewis Basicity Conductive Polymers toward Glycerol Upgrading Assisted Hydrogen Evolution

“…Through facile modification processes, these polymers can effectively modulate the electronic structure and charge distribution within the polymer matrix. − This phenomenon, in turn, exerts a profound influence on the adjacent electrocatalyst, offering a means to tailor its reactivity and selectivity. Furthermore, conducting polymers exhibit excellent conductivity, providing efficient pathways for electron transfer between the electrocatalyst and the electrode surface. − This feature is particularly advantageous in optimizing charge transport kinetics, thereby enhancing the overall electrocatalytic performance. Moreover, the inherent versatility of conducting polymers allows for facile integration with a variety of electrocatalytic materials, ranging from noble metals to earth-abundant transition metal-based catalysts.…”