Nitrogen-doped graphenes as efficient electrocatalysts for the selective reduction of carbon dioxide to formate in aqueous solution

Abstract

We report the first example of metal-free nitrogen-doped graphene-based materials for the electrochemical reduction of CO2to formate. The synthesized catalysts are highly active and stable in the electrocatalytic reduction of CO2to formate in an aqueous electrolyte.

Carbon Solving Carbon's Problems: Recent Progress of Nanostructured Carbon‐Based Catalysts for the Electrochemical Reduction of CO2

“…As demonstrated by Wang et al, their N-graphene achieved a stable chronoamperometric response over 12 h operation, with negligible change to the material's morphology as evidenced by SEM. [51] Similar observations have been made for other N-graphene materials, displaying very stable operation over long term operation and achieving better stability than polycrystalline metal electrodes like Au and Ag. [29,54] One reason for this improved stability and reduction in performance attenuation over polycrystalline metals is that N-graphene has been shown to be largely insensitive to CO and, therefore, it is not poisoned by CO 2 reduction products.…”

“…[51] Maximum FE toward formate production reached 73% at -0.84 V vs RHE, which is comparable to that of the high performing metal-free polyethylenimine/Ndoped carbon nanotube composites (PEI-NCNT; Figure 1c). [53] Shown in Figure 1d, the Tafel slope for the N-graphene electrode was found to be 135 mV dec -1 , which is similar to a ratelimited single e _ transfer (118 mV dec -1 ) and suggests that the rate determining step is the first e _ transfer to adsorbed CO 2 molecules on the electrode surface.…”

“…Wang et al note that pyridinic-N form the highest N functionality in their N-graphene (Figure 1e,f) which results in high bond polarity and hence, oxidised adjacent carbon atoms. [51] However, these oxidised carbon atoms are reduced through redox cycling and it is this reduction-oxidation cycling of active carbon atoms which they attribute to the high activity and stability.…”

“…which alter local electron density, active sites for the CO 2 RR can be formed. [29,50,51] Graphene materials have also been used as effective supports for metal nanoparticles active toward the CO 2 RR due to their large surface areas and excellent network conductivities, affording a metal-support synergy that enhances catalytic activity.…”

“…Similar findings have also been found for boron doped graphene (B-graphene). [50] Synthesis of graphene for CO 2 reduction catalysts has largely been via high temperature pyrolysis of GO, [50,51] but CVD methods have also been used, [29] and doping of heteroatoms has been performed with post treatment methods. N-doping in this way provides better control over final N content and moiety type, and has direct implications on electrochemical performance.…”