Reduction of Aqueous CO₂ to 1-Propanol at MoS₂ Electrodes

Abstract

Reduction of carbon dioxide in aqueous electrolytes at single-crystal MoS 2 or thin-film MoS 2 electrodes yields 1-propanol as the major CO 2 reduction product, along with hydrogen from water reduction as the predominant reduction process. Lower levels of formate, ethylene glycol, and t-butanol were also produced. At an applied potential of -0.59 V versus a reversible hydrogen electrode, the Faradaic efficiencies for reduction of CO 2 to 1-propanol were ~3.5% for MoS 2 single crystals and ~1% for thin films with low edge-site densities. Reduction of CO 2 to 1-propanol is a kinetically challenging reaction that requires the overall transfer of 18 e -and 18 H + in a process that involves the formation of 2 C-C bonds. NMR analyses using 13 CO 2 showed the production of 13 C-labelled 1-propanol. In all cases, the vast majority of the Faradaic current resulted in hydrogen evolution via water reduction. H 2 S was detected qualitatively when single-crystal MoS 2 electrodes were used, indicating that some desulfidization of single crystals occurred under these conditions.

Insights into the Photoassisted Electrocatalytic Reduction of CO2 over a Two‐dimensional MoS2 Nanostructure Loaded on SnO2 Nanoparticles

“…It is considered that this is due to the MoS 2 layer stack, causing a "pile up" effect, further leading to slow charge transfer. [23,35] The results are consistent with the other analysis. Controlled potential electrolysis was performed to investigate the effect of applied potentials on FE and current density for HCOOH production at 5 % MS/SON electrode.…”

“…In order to seek good catalytic activity, researchers have tried to combine the two kinds of materials by various methods. Francis [23] et al synthesized MoS 2 thin-film catalysts on Si wafers with 1-Propanol Faradaic efficiency of 45 % and high stability of more than 12 h. Jung [24] et al immobilized hierarchical structure of mesoporous TiO 2 on 3D graphene with few-layered MoS 2 , and they found that the hierarchical structure contributed CO photoconversion, and the conversion rate (92.33 μmol CO/g h) was much higher than those of other structural composite combinations. Qiao [25] et al prepared MoS 2 /SnO 2 PÀ N Heterojunctions for trimethylamine gas sensor, the results showed that with low loading of MoS 2 , the PÀ N heterojunction exhibited superior sensing selectivity and long-term stability toward trimethylamine.…”

Unveiling Electrochemical Reaction Pathways of CO2 Reduction to CN Species at S‐Vacancies of MoS2

“…In the previous section, we showed that multiple pathways startingf rom the adsorption of HCHO could open at À0.40 V. This value of h theory is consistent with the onset potential between À0.59 and À0.50 Vi ne xperiments associated with the formation of 1-propanol, the major CO 2 Rp roduct, but also ethylene glycol. [20] We note that the pH in the experiments was 6.8, which is slightly smaller than 7.0 in our calculations. This pH difference changed the h theory by approximately 0.01 V, barely affectingour conclusion.…”

“…[17][18][19] Recently,Francis et al investigated CO 2 Ro ns ingle-crystal MoS 2 in aqueous electrolyte, dis-covering1 -propanol (CH 3 CH 2 CH 2 OH)a sam ajor CO 2 Rp roduct at moderate overpotentials (%À0.59 Vv s. RHE), although the CO 2 Re fficiency was still outperformed by the hydrogen evolution reaction( HER). [20] This result is surprising because C 3 species are rarely produced as am ajor product of CO 2 Ro nk nown catalysts, particularly at such small overpotentials. The only exception that we are aware of are nickel phosphides, which were recentlyr eported to generate methylglyoxal (CH 3 COCHO) and ring-shaped 2,3-furandiol (C 4 H 4 O 3 )a sm ajor products.…”

“…To identify the active site of MoS 2 ,F rancis et al measured FE while changing the edge density of MoS 2 and found that the FE of the 1-propanol production decreased with increasing edge density. [20] This implies that the active site is likely to be present at the basal plane rather than the edges. However,t he clean surfaceo fM oS 2 is known to be inert, [22] and thus, the natureo ft he active site responsible for CO 2 Rt o1 -propanol is still elusive.…”