Vitamin B12‐Immobilized Graphene Oxide for Efficient Electrocatalytic Carbon Dioxide Reduction Reaction

Abstract

A naturally occurring water‐soluble cobalt‐complex cyanocobalamin (Vitamin B12) has been identified as a new and efficient electrocatalyst for the CO2‐to‐CO reduction reaction in aqueous solution. Heterogeneous B12‐electrocatalysts prepared by a simple electrochemical immobilization technique on graphene‐oxide (GO)‐modified glassy carbon and carbon paper (CP) electrodes, without any non‐degradable polymer‐binders, showed a highly stable and well‐defined surface‐confined redox peak at E’=−0.138 V vs. RHE with a surface‐excess value, ΓB12=4.28 nmol cm−2. This new electrocatalyst exhibits 93 % Faradaic efficiency for CO2‐to‐CO conversion at an electrolysis potential, −0.882 V vs. RHE (an optimal condition) with a high current density, 29.4 mA cm−2 and turn‐over‐frequency value, 5.2 s−1, without any surface‐fouling problem, in 0.5 m KHCO3. In further, it follows an eco‐friendly, sustainable and water‐based approach with the involvement of biodegradable and non‐toxic chemicals/materials like B12, GO and CP.

Cyclic iron tetra N-heterocyclic carbenes: synthesis, properties, reactivity, and catalysis

“…It is consecutively reduced to iron(0) and a CO 2 molecule coordinates to the highly nucleophilic iron center with presumably occupied d z 2 orbital due to the strong s-donating properties of the tetracarbene (see Section 4.4 for details). 227 This is in contrast to iron porphyrin complexes, where the reduction is ligand-centered and an intermediate-spin iron(II) center which is antiferromagnetically coupled to a porphyrin diradical anion is proposed. 228,229 The formation of CO in the absence of a proton source proceeds via disproportionation of two formal CO 2 À radical species to CO and CO 3…”

Graphene and its derivatives: understanding the main chemical and medicinal chemistry roles for biomedical applications

“…On the other hand, hydrophilic and amphiphilic polymers are efficiently absorbed over the sheets to provide a steric barrier and prevent restacking [ 161 ]. In addition, biomolecules such as proteins [ 162 ], peptides [ 163 ], and vitamins [ 164 ] are attractive from the standpoint of their safety and non-immunogenicity, enabling the biomedical applications of graphene.…”

Selective Electrocatalytic CO2 Reduction to CO by an NHC-Based Organometallic Heme Analogue

“…Key considerations that motivate the choice of these organometallic heme analogues are as follows: (i) the macrocyclic tetracarbene ligand scaffold is topologically similar to a porphyrin but is expected to be redox inactive, thus confining all redox chemistry to the central metal ion and (ii) the equatorial ligation with four very strong σ-donor NHCs pushes the d x 2 – y 2 orbital high in energy so that reduction of the Fe II (d 6 ) complex 1 2+ will necessarily populate its d z 2 orbital. Low-valent formal Fe 0 species are usually implicated as the reactive species in Fe-porphyrin-mediated CO 2 electroreduction, , but computational and spectroscopic studies revealed that the reduction is ligand-centered and that they are best described as having an intermediate-spin Fe II center that is antiferromagnetically coupled to a porphyrin diradical anion. , In contrast, an analogous Fe 0 species derived from tetra­(NHC)-based 1 0 may be expected to feature a (d z 2 ) 2 configuration, potentially exhibiting supernucleophilic behavior similar to that seen in reduced cobalamins . As an additional benefit, the macrocyclic tetra­(NHC) ligand platform offers a wide range of tunabilities including the modification of the ring size or the peripheral substituents at the NHC subunits. − …”

“…56,57 In contrast, an analogous Fe 0 species derived from tetra(NHC)-based 1 0 may be expected to feature a (d z 2 ) 2 configuration, potentially exhibiting supernucleophilic behavior similar to that seen in reduced cobalamins. 58 As an additional benefit, the macrocyclic tetra(NHC) ligand platform offers a wide range of tunabilities including the modification of the ring size or the peripheral substituents at the NHC subunits. 59−61 ■ RESULTS AND DISCUSSION Complex 1(OTf) 2 has been synthesized as previously reported.…”