Strategic catalyst modification for boosting CO concentration at electrode surface and easing selective CO reduction at higher potential

• Published in: Sustainable energy & fuels Vol. 7; no. 18; pp. 463 - 4637
• Main Authors: Mandal, Shuvojit, Kumar, Praveen
• Format: Journal Article
• Published: 12.09.2023
• ISSN: 2398-4902
• DOI: 10.1039/d3se00813d

Electrochemical CO 2 reduction offers an efficient route to store renewable energy in the form of carbon-based fuels via hydrogenation, and thus ensures a net-zero carbon emission energy cycle. However, the search for highly stable and selective catalyst material with an acceptable current density for the CO 2 reduction reaction (CO 2 RR) is ongoing. Therefore, the synthesis of novel materials or modifications of existing materials is one of the most pursued research subjects. Earth-abundant and environment-friendly low-cost 2D bismuth (Bi) with long-term stability casts a bright possibility in this regard with its high formate selectivity. Here, first, we demonstrated a controlled synthesis of (012) faceted 2D Bi flakes with uniform height via a chemical reduction of 2D BiOCl sacrificial template in a facile ambient atmosphere. These 2D Bi flakes were then deposited on carbon paper for electrochemical CO 2 RR, which manifested the partial formate current density of 18.7 mA cm −2 at −1.14 V RHE , while chronoamperometry was performed in CO 2 -saturated 0.5 M KHCO 3 electrolyte; a peak formate faradaic efficiency (FE) of ∼90% was observed at −0.84 V RHE . Furthermore, we have demonstrated how the redox-active conducting polymer, polyaniline (PANI), which alone is not even active for CO 2 RR, can significantly slow down the sharp drop in formate selectivity at higher potentials as compared to Bi flakes. When the 2D Bi flakes are soaked in PANI, the formate partial current density in chronoamperometry enhances to 35.5 mA cm −2 at −1.14 V RHE . Furthermore, we also correlated these phenomena in terms of different feasible mechanistic paths. PANI modification on the Bi flake surface enhances CO 2 concentration at the electrode surface which slows down formate selectivity drop at higher potential as compared to bare Bi flakes.