Copper-based catalysts have been recognized as promising candidates for electrochemical conversion of CO2 to value-added chemicals and synthetic fuels. Yet, the challenges of high overpotential and low product selectivity have motivated the rational electrode engineering. In the present work, we prepared CuS catalysts using different sulfur precursors, and we aimed to elucidate the precursor-dependent effect on their structure–property–activity relationships for electrochemical CO2 reduction. The different sulfur precursors exhibited varied S release rates in hydrothermal synthesis, which had induced distinct surface morphological features and diverse sulfur vacancy concentrations, and the intrinsic catalytic activity and product selectivity would be affected. The desired CuS-TU catalyst synthesized using thiourea as the sulfur precursor featured a flower-like morphology and had the highest sulfur vacancy concentration. The nanoflower morphology offered expanded space and considerable undercoordinated sites for facilitated interfacial mass transfer in electrochemical CO2 reduction. Density functional theory calculations confirmed that the abundant sulfur vacancy played an important role in strengthening the adsorption of the *COOH intermediates on the surface, which promoted CO production via the *COOH pathway. The CuS-TU catalyst therefore exhibited a relatively higher CO selectivity of 72.67% at −0.51 V vs RHE. These findings will provide more insights into improving the electrochemical CO2 reduction performance of copper-based catalysts by structure engineering.
Nanoporous CuS and Ag 2 S/CuS composite are synthesized by chemical dealloying method. The Ag 2 S content of the composite catalysts is controlled by Ag atom in the original amorphous alloys. The composite catalysts reveal an good activity for hydrogen evolution reaction (HER) with a small potential of ∼0.2 V when current density is 10 mA cm −2 and a high current density of 163.4 mA cm −2 at 400 mV overpotential, which is associated with the enriched active sites on CuS and the improved electrical conductivity by Ag 2 S. The Tafel slope of Ag 2 S/CuS (75 mV dec −1 ) indicates that the combination of VH (Volmer-Heyrovsky) and VT (Volmer-Tafel) mechanisms might be involved to produce molecular hydrogen over Ag 2 S/CuS catalysts and the rate-determining step is likely some other than purely Heyrovsky or Tafel step. In addition, the composites exhibit good durability in acidic electrolytes and this method would open up a new type of highly efficient electrocatalyst.
Ao Zhang,Zhongqing Jiang,Shaoda Zhang,Penghua Lan,Naihua Miao,Weiheng Chen,Ning Huang,Xiaoning Tian,Yangjie Liu,Zhongyu Cai
We report the development of non-noble transition metal sulfide catalysts Mn-CuS-x for high-efficiency and selective H 2 O 2 production. In this study, we synthesized Mn-CuS-x with coral-shaped hierarchical porous structure through one-pot hydrothermal reaction. The Mn-CuS-x possesses large specific surface area with plenty of crystalline defects via heteroatom doping of Mn. The Mn-CuS-x kinetically favored 2e − pathway over 4e − pathway, resulting in high selectivity (>92%) to H 2 O 2 production and high H 2 O 2 concentration (∼24.5 mM at 0.6 V vs. RHE) within 3 h for the optimized Mn-CuS-2 catalysts (synthesized with a molar ratio of 1:3:8 (MnCl 2 ·4 H 2 O: CuCl 2 ·2 H 2 O: C 2 H 5 NS)). The Mn-CuS-2 showed excellent stability, indicating that the Mn-CuS electrocatalysts can simultaneously achieve both high stability and enhanced H 2 O 2 production. Our first-principles calculations further confirmed that the heteroatom Mn doping to CuS thermodynamically makes the 2e – -ORR pathway more favorable. This study provides a green, low-cost, and efficient route to produce H 2 O 2 , which is very promising for generating chemicals and liquid fuels.
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