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Heteroatom doping can facilitate intrinsic activity via the tuning of electronic states. However, it is still rare to elucidate the role of a specific metal sulfide electronic state and simultaneously enhance the CO2 electroreduction reaction (CO2RR) stability. SnS is well-known for its ability to produce HCOOH; however, its long-term operational stability is limited by sulfur dissolution. Herein, we propose a strategy to reinforce the S atoms via heteroatom (In) doping. In situ Raman tests and theoretical calculations demonstrate that In atoms with fewer valence electrons (compared with Sn) can tune the electronic state of SnS and strengthen the S–metal bond energy. Consequently, sulfur dissolution was inhibited, and the reaction pathway was optimized. Further, the In-SnS/C achieves a Faradaic efficiency of 96.6% for formate at −0.6 V vs RHE and a catalyst stability of 50 h at a current density of ∼37 mA cm–2. This study shows that altering the electronic structure of SnS via heteroatoms is a strategy to optimize both the activity and stability of electrocatalysts for the CO2RR.

CO 2 RR) is regarded as one of the most attractive, which can not only convert CO 2 to high value hydrocarbon as fuels or chemical raw materials with high yields, but also be easily compatible to renewable energies. [2][3][4] Various hydrocarbons, that is, CO, HCOOH, CH 4 , C 2 H 4 , C 2 H 5 OH, etc., can be obtained during the CO 2 RR process. Among these products, multicarbon products (C 2+ ) are more attractive because of their higher economic values and higher energies densities with comparison to mono-carbon products (C 1 ). As one the most important products among C 2+ during CO 2 RR process, C 2 H 4 has attracted increasing interests owing to its wide applications as an important raw material for global chemical industries. However, as the conversion from CO 2 to C 2 H 4 involves CC coupling and diverse reaction pathways, it is more complex and difficult to produce C 2 H 4 than C 1 products during CO 2 RR process. As a result, the selectivity and activity for C 2 H 4 production is usually much lower than that for C 1 products. [5][6][7][8] In terms of the materials for C 2 H 4 production, Cu based materials are the most suitable candidates owing to the moderate adsorption of CO intermediates and the subsequent promotion for CC coupling. [9][10][11] Recently, great efforts have been made and various strategies have been developed to improve the C 2 H 4 selectivity and activity of Cu based materials, such as crystallinity [12] and size control [13] to enhance the CO 2 adsorption and activation barrier, facet engineering, [14][15][16] doping and defect engineering, [17,18] grain boundary, [19,20] oxidation state, [21][22][23][24][25][26] and surface molecule engineering [27,28] to enhance the CO stability and promote CC coupling, etc. Although, the C 2 H 4 selectivity and activity has been greatly improved, the maximum value for C 2 H 4 faradaic efficiency (FE C2H4 ) is still not high enough to meet the criteria for practical applications. Therefore, from the aspect for practical applications, it is still necessary and a great challenge to further improve the selectivity and activity for C 2 H 4 production.Comparing to the relatively low selectivity of C 2 H 4 , the selectivity for C 2 products could be much higher (80-90%), as other C 2 products, such as C 2 H 5 OH, CH 3 CHO, CH 3 COOH, could be inevitably produced besides C 2 H 4 during CO 2 RR process. [9,17,29] The electrochemical CO 2 reduction reaction (CO 2 RR) has great potential in realizing carbon recycling while storing sustainable electricity as hydrocarbon fuels. However, it is still a challenge to enhance the selectivity of the CO 2 RR to single multi-carbon (C 2+ ) product, such as C 2 H 4 . Here, an effective method is proposed to improve C 2 H 4 selectivity by inhibiting the production of the other competitive C 2 products, namely C 2 H 5 OH, from Cu 2 O/C composite. Density functional theory indicates that the heterogeneous structure between Cu 2 O and carbon is expected to inhibit C 2 H 5 OH production and promote CC coupling, which fac...

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