Ag₂S/MoS₂ Nanocomposites Anchored on Reduced Graphene Oxide: Fast Interfacial Charge Transfer for Hydrogen Evolution Reaction

Abstract

Hydrogen evolution reaction through electrolysis holds great potential as a clean, renewable, and sustainable energy source. Platinum-based catalysts are the most efficient to catalyze and convert water into molecular hydrogen; however, their large-scale application is prevented by scarcity and cost of Pt. In this work, we propose a new ternary composite of Ag2S, MoS2, and reduced graphene oxide (RGO) flakes via a one-pot synthesis. The RGO support assists the growth of two-dimensional MoS2 nanosheets partially covered by silver sulfides as revealed by high-resolution transmission electron microscopy. Compared with the bare MoS2 and MoS2/RGO, the Ag2S/MoS2 anchored on the RGO surface (the ternary system Ag2S/MoS2/RGO) demonstrated a high catalytic activity toward hydrogen evolution reaction (HER). Its superior electrochemical activity toward HER is evidenced by the positively shifted (−190 mV vs reversible hydrogen electrode (RHE)) overpotential at a current density of −10 mA/cm2 and a small Tafel slope (56 mV/dec) compared with a bare and binary system. The Ag2S/MoS2/RGO ternary catalyst at an overpotential of −200 mV demonstrated a turnover frequency equal to 0.38 s–1. Electrochemical impedance spectroscopy was applied to understand the charge-transfer resistance; the ternary sample shows a very small charge-transfer resistance (98 Ω) at −155 mV vs RHE. Such a large improvement can be attributed to the synergistic effect resulting from the enhanced active site density of both sulfides and to the improved electrical conductivity at the interfaces between MoS2 and Ag2S. This ternary catalyst opens up further optimization strategies to design a stable and cheap catalyst for hydrogen evolution reaction, which holds great promise for the development of a clean energy landscape.

Pore Surface Engineering of Covalent Triazine Frameworks@MoS2 Electrocatalyst for the Hydrogen Evolution Reaction

“…The equivalent circuits of EIS data for all the catalysts are shown in Figure S17. [48] Cyclic voltammetry (CV) measurements ( Figure 4d)s how that after 3000c ycles the last polarization curve almost coincides with the first one, and the loss of current density can be ignored. [46,47] Therefore, double-layer capacitance is another way to understand catalytic activity surface area.…”

“…(Figure 5, Figure S18) The values of the double-layer capacitance (C dl )w ere calculated as 2.0, 6.6, 8.1, 9, 11.6, 12.1, 13.6, 11.7, and 2.6 mF cm À2 for CTFs, CTFs@MoS 2 -X (X = 0.1, 0.2, 0.5, 1, 2, 5, 10), and MoS 2 .I ti sasignificant indicationf or the increased active surface sites int his system.T he higher C dl catalyst can provide ah igh reaction site density for adsorption, which is conducive to effective charget ransfer and has a higher catalytic activity. [48] Cyclic voltammetry (CV) measurements ( Figure 4d)s how that after 3000c ycles the last polarization curve almost coincides with the first one, and the loss of current density can be ignored. It is indicated that CTFs@MoS 2 -5h ave the excellent stabilityf or high-efficiency HER.…”

Engineered 2D Transition Metal Dichalcogenides—A Vision of Viable Hydrogen Evolution Reaction Catalysis

“…[ 141 ] The charge transfer issue has also been considered in building other hybrid structures for the promoted HER, such as the Ag 2 S/MoS 2 and MoO 2 /MoS 2 nanocomposites. [ 142–144 ]…”

Molybdenum Disulphide Heterointerfaces as Potential Materials for Solar Cells, Energy Storage, and Hydrogen Evolution

“…Its characterization confirmed that r‐GO supports the growth of 2D MoS 2 nanosheets partially covered by Ag 2 S. These composites showed a superior electrochemical hydrogen evolution as compared with the bare MoS 2 and MoS 2 /r‐GO electrodes. This behavior has been attributed to both a small charge transfer resistance (98 Ω) at −155 mV versus RHE and the enhanced active site density in composites . In another work a lamellar heterostructure of MoS 2 nanodots and metallic VS 2 nanosheets (MoS 2 NDs/VS 2 ) were grown by the in situ hydrothermal technique to check their electrochemical activity.…”