Hydrogen evolution reaction from bare and surface-functionalized few-layered MoS2 nanosheets in acidic and alkaline electrolytes

Abstract

Hydrogen is considered as an ideal and sustainable energy carrier because of its high energy density and carbon-free combustion. Electrochemical water splitting is the only solution for uninterrupted, scalable, and sustainable production of hydrogen without carbon emission. However, a large-scale hydrogen production through electrochemical water splitting depends on the availability of earth-abundant electrocatalysts and a suitable electrolyte medium. In this article, we demonstrate that hydrogen evolution reaction (HER) performance of electrocatalytic materials can be controlled by their surface functionalization and selection of a suitable electrolyte solution. Here, we report syntheses of few-layered MoS2 nanosheets, NiO nanoparticles (NPs), and multiwalled carbon nanotubes (MWCNTs) using scalable production methods from earth-abundant materials. Magnetic measurements of as-produced electrocatalyst materials demonstrate that MoS2 nanoflakes are diamagnetic, whereas surface-functionalized MoS2 and its composite with carbon nanotubes have strong ferromagnetism. The HER performance of the few-layered pristine MoS2 nanoflakes, MoS2/NiO NPs, and MoS2/NiO NPs/MWCNT nanocomposite electrocatalysts are studied in acidic and alkaline media. For bare MoS2, the values of overpotential (η10) in alkaline and acidic media are 0.45 and 0.54 V, respectively. Similarly, the values of current density at 0.5 V overpotential are 27 and 6.2 mA/cm2 in alkaline and acidic media, respectively. The surface functionalization acts adversely in the both alkaline and acidic media. MoS2 nanosheets functionalized with NiO NPs also demonstrated excellent performance for oxygen evolution reaction with anodic current of ~60 mA/cm2 and Tafel slope of 78 mVdec−1 in alkaline medium.

Simultaneous Piezoelectrocatalytic Hydrogen‐Evolution and Degradation of Water Pollutants by Quartz Microrods@Few‐Layered MoS2 Hierarchical Heterostructures

“…Figure 4k further shows that quartz-MRs PENG generated a charge of ≈4.6 V, indicating that quartz MR can be used for a parallel plate capacitor, which is self-powered by mechanical force to provide an electric field for piezoelectrocatalytic HER. In general, for the few-layered MoS 2 nanosheets, the values of overpotential in both alkaline and acidic solution are less than 0.54 V, [49] which is lower enough to be powered by quartz MRs based on our simulated and experimental results.…”

Fabrication of Coral‐Shaped MoS2@Ni(Mn)VOX Electrocatalyst for Efficient Alkaline Hydrogen Evolution

“…[ 51 ] Figure 3g shows the spectrum of S 2 p . Two diffraction peaks at 162.4 and 163.7 eV correspond to S 2 p 3/2 and S 2 p 1/2 respectively, [ 52 ] which are consistent with MoS 2 . In addition, there is a diffraction peak at 167.5 eV, which can be seen as SO 4 2− , according to the comparison table of the XPS electron binding energy, indicating that the electrode was partially oxidized by air.…”

Carbon Nanohorn-Based Electrocatalysts for Energy Conversion

“…In general, transition metal dichalcogenides (TMDs) are able to minimize overpotential for HER and lower Tafel slope values due to their innate catalytic activities [ 141 ]. Hence, they have been massively studied and employed in the development of electrocatalysts for HER with various architectures [ 142 , 143 , 144 , 145 , 146 ]. Moreover, carbon-based nanomaterials, like graphene and heteroatom-doped graphene, have been effectually combined with TMDs (MoS 2 , WS 2 , MoSe, etc.…”