Electrochemical and SECM Investigation of MoS₂/GO and MoS₂/rGO Nanocomposite Materials for HER Electrocatalysis

Abstract

Development of advanced materials for electrocatalytic and photocatalytic water splitting is the key in utilization of renewable energy. In the present work, we have synthesized MoS 2 nanoparticles embedded over the graphene oxide (GO) and reduced graphene oxide (rGO) layer for superior catalytic activity in the hydrogen evolution process (HER). The nanocomposite materials are characterized using different spectroscopic and microscopic measurements. A Tafel slope of ∼40 mV/decade suggested the Volmer–Heyrovsky mechanism for the HER process with MoS 2 /GO composite as the catalyst, which indicated that electrochemical desorption of hydrogen is the rate-limiting step. The small Tafel slope indicates a promising electrocatalyst for HER in practical application. MoS 2 /GO composite material has shown superior catalytic behavior compared to that of MoS 2 /rGO composite material. The HER catalytic activity of the catalysts is explored using scanning electrochemical microscopy (SECM) using the feedback and redox competition mode in SECM. The activation energy for HER activity was calculated, and the values are in the range of 17–6 kJ/mol. The lower value of activation energy suggested faster HER kinetics.

Photocatalytic Simultaneous Removal of Nitrite and Ammonia via a Zinc Ferrite/Activated Carbon Hybrid Catalyst under UV–Visible Irradiation

“…Therefore, AC improved the adsorption of NN and AN and harvesting of incident light of λ > 530 nm wavelength, resulting in the enhanced photocatalytic activity. 51,52…”

Local probe investigation of electrocatalytic activity

“…45 An improvement in MoS 2 activity can be obtained by incorporating it into matrices with high conductivity. 213 This was done by Kumar et al 214 who combined MoS 2 NPs of the T1 phase with graphene oxide (GO) or reduced graphene oxide (rGO) in which case both composites exhibited comparable HER activity to the state-of-the-art Pt/C. 214 On the other hand, nickel foams with a karst landform structure were studied for their HER activity by Gao et al 215 through SG/TC mode, a Pt nanoelectrode and Si substrate.…”

Hydrothermally Synthesized MoS2 Nanoclusters for Hydrogen Evolution Reaction

“…Figure 3b shows the Bode plot, impedance modulus [log j Z j] vs. log f at over-potential which followed the trend of Nyquist plot and provides direct view of impedance (modulus) for each frequency range. The Bode phase plot (Figure 3c) shows the maximum phase angle~47°, where the lower phase angle maxima suggest a fast-faradaic process of MoS 2 nanoclusters [23][24][25].…”