Vitamin B₁₂ on Graphene for Highly Efficient CO₂ Electroreduction

Abstract

Combining the advantages of homogeneous and heterogeneous catalytic systems has emerged as a promising strategy for electrochemical CO 2 reduction although developing robust, active, product-selective, and easily available, catalysts remains a major challenge. Herein, we report the electroreduction of CO 2 catalyzed by cobalt and benzimidazole containing Vitamin B 12 immobilized on the surface of reduced graphene oxide (rGO). This hybrid system with a naturally abundant molecular catalyst produces CO with high selectivity and a constant current density in an aqueous buffer solution (pH 7.2) for over 10 h. A Faradaic efficiency (FE) of 94.5% was obtained for converting CO 2 to CO at an overpotential of 690 mV with a CO partial current density (j CO ) of 6.24 mA cm −2 and a turnover frequency (TOF) of up to 28.6 s −1 . A higher j CO (13.6 mA cm −2 ) and TOF (52.4 s −1 ) can be achieved with this system at a higher overpotential (790 mV) without affecting the product selectivity (∼94%) for CO formation. Our experimental findings are corroborated with density functional theory (DFT) studies to understand the influence of the covalently attached and redox-active benzimidazole unit. To the best of our knowledge, this is the first example of naturally abundant vitamin being immobilized on a conductive surface for highly efficient CO 2 electroreduction.

Atomically Dispersed Ni/Cu Dual Sites for Boosting the CO2 Reduction Reaction

“…To understand the reaction kinetics of the prepared samples, Tafel analysis was performed as shown in Figure f. The plotted logarithm of J CO vs overpotential for Ni/Cu–N–C is linear from 0.064 to 0.164 V with a Tafel slope of 86 mV dec –1 , suggesting the first electron transfer that forms surface adsorbed *COOH intermediates as the rate-determining step. ,− Compared with Ni–N–C (94 mV dec –1 ), Cu–N–C (120 mV dec –1 ), and N–C (206 mV dec –1 ), Ni/Cu–N–C has the smallest Tafel slope, confirming its improved kinetics for the CO 2 to CO conversion, benefiting from the synergistic Ni/Cu dual sites. Such fast reaction kinetics are also evidenced in the electrochemical impedance spectroscopy (EIS) measurements (Figure S15).…”

Assembly of a Highly Efficient Molecular Device with (CNCbl)‐MWCNT/CP as Electrode for CO2 Reduction Coupled to Water Oxidation

“…In its chemical structure, four of the six‐coordinate on sites are provided by the corrin ring, and a fifth by a dimethylbenzimidazole moiety (Scheme 1). [9] According to previous reports, [9–10] CNCbl can act as an electrocatalyst for both CO 2 reduction and water oxidation. Herein, a highly efficient molecular device using CNCbl‐MWCNT/CP (CP: carbon paper) as a bifunctional electrode was assembled for simultaneously electrolyzing CO 2 /H 2 O into CO/O 2 in an aqueous solution.…”

Cobalt Electrocatalyst on Fluorine Doped Carbon Cloth – a Robust and Partially Regenerable Anode for Water Oxidation

“…Encouragingly, exciting progress has been made in recent years regarding the immobilization or anchoring of molecular WO catalysts onto conductive supports. [16][17][18][19][20][21]24] This strategy takes advantage of both the mechanistic understanding obtained from molecular systems, and the improved stability typically observed for catalysts immobilized on a conductive surface.…”

“…This research has generated a new group of electro-materials with improved TONs and TOFs . [17,18,21,23,24] Fluorine-doped carbon cloth (FCC) has recently emerged as robust and conductive support for various electrochemical systems. [23,25] Due to the high stability and hydrophobicity of its surface CÀ F bonds, it tolerates further structural modifications under harsh reaction conditions without its intrinsic properties being compromised.…”

“…[26] We have previously reported on a naturally abundant cobalt-containing catalyst, consisting of vitamin-B 12 immobilized by π-π stacking interaction onto reduced graphene oxide surfaces with a carbon paper support, as an efficient electrode for electrochemical carbon dioxide reduction. [24] We envisioned that having covalent bonding interactions between the catalyst and the conductive surface might improve the electrocatalytic performance further. However, the complex structure of the naturally occurring vitamin-B 12 molecule does not allow for straightforward structural modifications to help improve covalent bonding interactions with the conductive surface.…”