Carbon Dioxide Electroreduction at Highly Porous Nitrogen and Sulfur Co-Doped Iron-Containing Heterogeneous Carbon Gel

Abstract

The functionalized carbon nanostructure, nitrogen and sulfur co-doped iron-containing highly porous carbon gel (obtained via carbonization of corresponding organic gel) is considered here as a non-precious metal catalyst for the electroreduction of carbon dioxide in neutral solution (potassium bicarbonate at pH = 6.8). Various electrochemical measurements (performed in distinct modes and under different conditions) have been utilized to comment about the catalyst performance and the reaction mechanism, in particular about the reaction products and the relative contribution from hydrogen evolution. At low overpotentials, the carbon dioxide reduction is favored over the hydrogen evolution reaction. Combination of conventional (stationary) stripping-type and hydrodynamic (rotating ring-disk electrode) voltammetric approaches has been demonstrated to function as an unique electroanalytical tool here. The CO 2 -reduction products can be identified as adsorbates (oxidative stripping voltammetry) or monitored continuously (electrooxidation) at the Pt ring electrode. Finally, the results of both electrochemical diagnostic and parallel gas chromatographic analytical measurements are consistent with the view that, in the examined range of the potentials, CO is the main CO 2 -reduction product. The electrochemical reduction of carbon dioxide (CO 2 ) permits, in principle, selective generation of carbon-based fuels (or syngas) and, indirectly, lowering population of one of green-house gases in the atmosphere. Due to existence of two strong C=O bonds in the CO 2 molecule, its electroreduction requires high overpotentials, and the low reaction efficiency still remains fundamental problem limiting practical applications. 1-3During recent years, various catalysts, including noble and non-noble transition metals, as well as their numerous coordination compounds, have been considered as catalysts for CO 2 electroreduction. [4][5][6][7][8][9][10] It has been demonstrated that selectivity of the process depends largely on the activating adsorptive (CO 2 ) phenomena and the affinity of catalytic centers to adsorbed carbon monoxide intermediate. 11 Depending on the strength of adsorption and according to the Sabatier principle, CO may be further protonated or hydrogenated to CHO adsorbate. This step is often considered as the rate-determining one during the hydrocarbon formation.12 It should be noted here that, for example, copper is capable of successfully catalyzing electroreduction of CO 2 to multicarbon products, 13-15 palladium induces the reaction mainly to CO and H 2 and only small amounts of formate. 2,[16][17][18][19] Another important practical issue is related to the need of lowering costs of catalysts by substituting the noble metals with inexpensive abundant elements. There has been growing interest in catalysts based on nanostructured carbons that include the metal-free Ndoped systems and the metal-containing carbons. [20][21][22][23][24][25][26] For example, the biomimetic centers containing metallic moieties in the vi...

A Disquisition on the Active Sites of Heterogeneous Catalysts for Electrochemical Reduction of CO2 to Value‐Added Chemicals and Fuel

“…Another strategy with carbon nanomaterial is to dope it with two functional groups and there are many examples of such double‐doped carbon for HER, ORR, and OER application . The benefit of dual doping can also be extended for CO 2 RR with N,S codoped highly porous carbon gel and polymer‐derived carbon catalysts are reported to be active for CO 2 RR . Similarly, a N, S doped porous carbon membrane was shown to demonstrate a FE CO of 94% with a very high j of −103 mA cm −2 at an applied potential of −0.7 V .…”

“…[270,[300][301][302][303] The benefit of dual doping can also be extended for CO 2 RR with N,S codoped highly porous carbon gel and polymer-derived carbon catalysts are reported to be active for CO 2 RR. [304,305] Similarly, a N, S doped porous carbon membrane was shown to demonstrate a FE CO of 94% with a very high j of −103 mA cm −2 at an applied potential of −0.7 V. [306] DFT calculations indicate that the co-doping of N and S within carbon can significantly reduce the free energy of rate determining *COOH radical, allowing the attainment of exceptional catalytic activity.…”

Metal–Nitrogen–Carbon Electrocatalysts for CO2 Reduction towards Syngas Generation

“…M-N-Cand N-C electrocatalysts that do not exhibit asuitable potential for syngas generation, or ar ange of products that is far from being limitedt oC Oa nd H 2 ,a re not reported (see Refs. [50,52,53,[64][65][66]).…”

Role of Heteroatoms in S,N‐Codoped Nanoporous Carbon Materials in CO2 (Photo)electrochemical Reduction

“…[17] CO was the main product and traces of methane werea lso detected.T he catalysts howedt he highest FE of 85 %a tÀ1.3 V( vs. RHE) for CO. However,t he role of sulfur in the CO 2 ERR was not thoroughly discussed. [17] CO was the main product and traces of methane werea lso detected.T he catalysts howedt he highest FE of 85 %a tÀ1.3 V( vs. RHE) for CO. However,t he role of sulfur in the CO 2 ERR was not thoroughly discussed.…”

“…Recently,n itrogen-and sulfur-codoped iron-containing highly porous carbon gel has been studied for the CO 2 electroreduction reactioni na na queous electrolyte. [17] CO was the main product and traces of methane werea lso detected.T he catalysts howedt he highest FE of 85 %a tÀ1.3 V( vs. RHE) for CO. However,t he role of sulfur in the CO 2 ERR was not thoroughly discussed. Metal-frees ulfur-containing nanoporous carbon has been tested in our previous study.…”