An advanced PdNPs@MoS2 nanocomposite for efficient oxygen evolution reaction in alkaline media

Abstract

In response to the increasing availability of hydrogen energy and renewable energy sources, molybdenum disulfide (MoS₂)-based electrocatalysts are becoming increasingly important for efficient electrochemical water splitting. This study involves the incorporation of palladium nanoparticles (PdNPs) into hydrothermally grown MoS₂via a UV light assisted process to afford PdNPs@MoS₂ as an alternative electrocatalyst for efficient energy storage and conversion. Various analytical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS), were used to investigate the morphology, crystal quality, and chemical composition of the samples. Although PdNPs did not alter the MoS₂ morphology, oxygen evolution reaction (OER) activity was driven at considerable overpotential. When electrochemical water splitting was performed in 1.0 M KOH aqueous solution with PdNPs@MoS₂ (sample-2), an overpotential of 253 mV was observed. Furthermore, OER performance was highly favorable through rapid reaction kinetics and a low Tafel slope of 59 mV dec^-1, as well as high durability and stability. In accordance with the electrochemical results, sample-2 showed also a lower charge transfer resistance, which again provided evidence of OER activity. The enhanced OER activity was attributed to a number of factors, including structural, surface chemical compositions, and synergistic effects between MoS₂ and PdNPs.

Scheme 1. Schematic view of palladium nanoparticles deposited on MoS₂ nanostructures.

Fig. 1. Powder XRD diffraction of (a) MoS₂ pristine (b, c) sample-1 & sample-2.

Fig. 2. SEM and EDS spectra of (a) MoS₂ pristine (b, c) sample-1 & sample-2.

Fig. 3. TEM micrographs a different magnification of pristine MoS₂ (a–c) and PdNPs@MoS₂ (d–f). (c, e) HRTEM micrographs with inset illustrating the spatial frequencies of the crystallite displayed in the FFT.

Fig. 4. XPS spectra of pristine MoS₂ and Pd doped sample-2 (a) Mo 3d, (b) S 2p, (c) Pd 3d.

Fig. 5. (a) LSV Polarization curves of different catalysts (b) bar graph presentation of different materials (c) corresponding Tafel plots for the different materials obtained from their LSV curves (d) C_dl values assigned to ECSA values (e & f) chrono-potentiometric durability at different current densities (20, 40 & 60 mA cm⁻²) of sample-2 and LSV curves before and after durability illustrating stability sample-2.

Fig. 6. EIS experiment data of MoS₂ pristine, different PdNPs@MoS₂ like sample-1 and sample-2 at OER onset potential, amplitude of 10 mV for the frequency range of 100 kHz to 0.1 Hz in 1.0 M KOH (a, b) Bode plots and (c) Nyquist plot.