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

Abstract

Although C1 species such as CO and CH4 constitute the majority of CO2 reduction (CO2 R) products on known catalysts, recent experiments showed that 1‐propanol with two C−C bonds is produced as the main CO2 R product on MoS2 single crystals in aqueous electrolytes. Herein, the CO2 R mechanism on MoS2 is investigated by using first‐principle calculations. Focusing on S‐vacancies (VS) as the catalytic site, potential free‐energy pathways to various CO2 R products are obtained by means of a computational hydrogen electrode model. The results underline the role of HCHO, which is one of the elemental C1 products, in opening pathways to CN species for N>1. Key steps to increase C−C bonds are the adsorption of HCHO at the VS site and binding of another HCHO to the adsorbed one. The predicted products and theoretical working potentials to open their pathways are consistent with experiments, which indicates that VS is an important active site for CO2 R on the MoS2 basal plane.

Photo/electrochemical Carbon Dioxide Conversion into C3+ Hydrocarbons: Reactivity and Selectivity

“…Although the smooth surfaces of the MoS 2 are proved to be catalytically inert, [36] hence the active sites may be at the basal planes, not the edges. In this regard, Kang et al [37] . used the first principle (ab initio) calculations to study the CO 2 electroreduction into C 2+ and higher hydrocarbons mechanisms on basal planes of MoS 2 .…”

“…The sulfur‐vacancies of MoS 2 (V s ) can be produced in a 10% fraction during the MoS 2 film fabrications. These V s are considered to be the active sites for the hydrogen evolution reaction (HER) [37] . The study showed that bowl shape V s are the active sites for the formaldehyde intermediate, which is the key to forming a multi‐carbon product formed at the first protonation step.…”

Identification of Active Sites for CO2 Reduction on Graphene‐Supported Single‐Atom Catalysts

“…Besides transition metals, a variety of materials such as transition metal dichalcogenides, [9][10][11] nickel sulfides, [12] and single-atom-doped carbons [13][14][15][16][17][18][19][20][21][22][23][24][25] are attracting recent attentions as potential heterogeneous catalysts, especially for CO 2 R. In particular, transition metal-and nitrogen-codoped graphene (referred to as MÀ NÀ G, where M is a transition metal) has emerged as an important type of single-atom CO 2 R catalysts that produce CO with a remarkable activity and efficiency. For example, Ju et al discovered that MÀ NÀ G catalysts (M=Mn, Fe, Co, Ni, and Cu) selectively converts CO 2 into CO with small onset potentials (> À 0.3 V vs. RHE) and high faradaic efficiencies (FEs; > 60 % in the case of M=Fe and Ni).…”

Defect Control in the Synthesis of 2 D MoS2 Nanosheets: Polysulfide Trapping in Composite Sulfur Cathodes for Li–S Batteries

“…MoS 2 is a 2 D material of increasing research interest recently owing to its interesting physical and electronic properties, including high conductivity, high surface area, and active sites for a diversity of applications . Previous reports relevant to Li–S batteries have used MoS 2 as a means to inhibit or anchor PS species during electrochemical cycling .…”

“…[12,13] MoS 2 is a2Dm aterialo fi ncreasing research interest recently owing to itsi nterestingp hysical and electronic properties, including high conductivity,h ighs urfacea rea, and active sites for ad iversity of applications. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Previous reports relevant to Li-S batteries have used MoS 2 as am eans to inhibit or anchor PS speciesduring electrochemical cycling. [29] These can be generalized into three strategies using MoS 2 :p rotection by augmenting the separator,t he Li-metala node, and PS trapping by inclusion in ac omposite cathode.…”