RhMoS₂ Nanocomposite Catalysts with Pt‐Like Activity for Hydrogen Evolution Reaction

Abstract

High overpotentials and low efficiency are two main factors that restrict the practical application for MoS 2 , the most promising candidate for hydrogen evolution catalysis. Here, RhMoS 2 nanocomposites, the addition of a small amount of Rh (5.2 wt%), exhibit the superior electrochemical hydrogen evolution performance with low overpotentials, small Tafel slope (24 mV dec −1 ), and long term of stability. Experimental results reveal that 5.2 wt% RhMoS 2 nanocomposite, even exceeding the commercial 20 wt% Pt/C when the potential is less than −0.18 V, exhibits an excellent mass activity of 13.87 A mg metal −1 at −0.25 V, four times as large as that of the commercial 20 wt% Pt/C catalyst. The hydrogen yield of 5.2 wt% RhMoS 2 nanocomposite is 26.3% larger than that of the commercial 20 wt% Pt/C at the potential of −0.25 V. The dramatically improved electrocatalytic performance of RhMoS 2 nanocomposites may be attributed to the hydrogen spillover from Rh to MoS 2 .broad range of applications. [24] The reason for these deficiencies may be due to the fact that MoS 2 has a relatively large Gibbs free energy (ΔG H ) of 0.08 eV. [23] There is a well-known volcano-type relation for HER catalysts, indicating that the optimal catalysts should exhibit a moderate Gibbs free energy for atomic hydrogen adsorption: [23,25] the catalysts with large ΔG H will fail to bind to hydrogen atoms and no evolution will take place; and the catalysts with small ΔG H will get blocked by hydrogen atoms and the subsequent hydrogen evolution becomes depressed. Therefore, MoS 2 needs to combine some materials with small ΔG H to fabricate composite catalysts, which may accelerate the rates of hydrogen adsorption and subsequent hydrogen evolution at different surfaces of catalysts, respectively. Ideally, the H adsorption takes place at a surface with small ΔG H ; while the hydrogen evolution occurs at a surface with large ΔG H . Such reasonably-designed composite catalysts might exhibit a high activity, even better than Pt catalyst.In this work, we employed noble metals and MoS 2 , as the strong H-adsorbed and quick H 2 -desorbed components respectively, to fabricate composite electrocatalysts (denoted as x wt% metal/MoS 2 , x means the relative mass ratio of noble metal in the composite) for HER. A systematical investigation was conducted for HER based on metal-MoS 2 nanocomposites by an in situ growth process.Among the investigated metal-MoS 2 nanocomposites, RhMoS 2 catalysts exhibit the most excellent HER activity. The optimal RhMoS 2 catalyst contains only 5.2 wt% Rh. Its Tafel slope (24 mV dec −1 ) is lower than that of the commercial 20 wt% Pt/C (30 mV dec −1 ); and its hydrogen product at −0.25 V is 26.3% larger than that of the Pt/C catalyst. The excellent HER performance of RhMoS 2 may be attributed to the hydrogen spillover from Rh to MoS 2 .

Engineering Multimetallic Aerogels for pH‐Universal HER and ORR Electrocatalysis

“…In comparison with widely investigated Pt‐based systems, only a few studies explored Rh‐based materials as HER catalysts, [ 33,34 ] presumably because of an inferior HER activity of rhodium as compared to other noble metals. Therefore, it is interesting to understand the underlying mechanisms accounting for the impressive performance of the Au–Rh aerogel electrocatalyst demonstrated in this work, which are proposed as below.…”

Boosting the Photoluminescence of Monolayer MoS2 on High‐Density Nanodimer Arrays with Sub‐10 nm Gap

“…One of the intriguing properties of MoS 2 is an indirect to a direct bandgap transition occurring when the thickness is reduced to a monolayer. [1b,2] 2D MoS 2 exhibits unique electric features and peculiar optical characteristics, which have been explored for applications ranging from optoelectronics, photonics, and nonlinear optics to photocatalysis, chemical synthesis, and biosensing . However, monolayer MoS 2 exhibits a relatively low quantum yield due to defect‐mediated nonradiative recombination and biexcitonic recombination at higher excitation powers .…”

Significantly Enhanced Hydrogen Evolution Activity of Freestanding Pd‐Ru Distorted Icosahedral Clusters with less than 600 Atoms

“…Thus, the measured Tafel slope of the freestanding Pd‐Ru distorted ico‐clusters suggests a Volmer–Tafel mechanism has an effect for this catalyst, where the chemical desorption is the rate‐limiting step. The Tafel slopes required for starting the HER on various reported catalysts are compared in Figure c. The reported catalysts show a 2–100 mV dec −1 decrease in the Tafel slope relative to that of the documented catalyst (Table S1 in the Supporting Information) . The fast HER kinetics enabled this freestanding Pd‐Ru distorted ico‐cluster catalyst to reach a high current density of 10 mA cm −2 at an η value as low as 26 mV.…”