No abstract

The strong affinity of palladium (Pd) towards hydrogen is the main challenge for hydrogen desorption application. Therefore, in this report, we synthesized nickel, copper, and cobalt core and palladium shell nanostructure supported on nitrogen, sulfur‐doped reduced graphene oxide (M@Pd/N, S‐rGO, M=Ni, Cu, Co) by hydrothermal method followed by reduction of the metal nanoparticles using modified polyol method. Using X‐ray diffraction (XRD), Raman spectroscopy, High resolution transmission electron microscope (HRTEM), Field emission scanning electron microscope (FESEM), and X‐ray photoelectron spectroscopy (XPS), the physicochemical properties of the synthesized sample was investigated. The results confirm strong interactions between M@Pd and higher surface area support that could enhance electrocatalytic activity towards hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Among the synthesized electrocatalyst, Ni@Pd/N,S‐rGO exhibits higher electrocatalytic activity with small over potential 0.035 V and 0.2 V at 10 mA/cm2 and a Tafel slope value of 39 mV dec−1 and 34 mV dec−1 for HER and OER, respectively. The Ni@Pd/N,S‐rGO electrocatalyst demonstrated excellent stability with a negligible current decrease for 12 h. The Cdl calculation shows a result of 2.2 mF μg−1 for Ni@Pd/N,S‐rGO, 1.9 mF μg−1 for Cu@Pd/N,S‐rGO, and 1.5 mF μg−1 for Co@Pd/N,S‐rGO.

Support materials are very crucial in noble metal electrocatalyst synthesis. They improve the catalytic activity of the noble metal by increasing their conductivity, surface area, and interactions. This report investigates the effect of support material on palladium nanoparticles’ electrochemical activity towards hydrogen evolution reaction. The structural and morphological study was conducted using x-ray diffraction (XRD), Raman Spectroscopy, and Field Emission Scanning Electron Microscope (FE-SEM) that confirmed the support material has a significant effect on the structure of nanocomposite. The hydrogen evolution (HER) performance of the synthesized electrocatalyst was evaluated in 0.5 M H2SO4. The Pd-Ni/g-C3N4 has higher catalytic activity with a lower overpotential of 55 mV at 10 mA cm2 current density and Tafel slope value 56 mV.dec−1 than other support material studied. The overpotential at 10 mA cm2 and Tafel slope value for electrocatalyst studied respectively are:- Pd/MoS2/CB( 78 mV at 10 mA cm2 and 57 mV.dec−1), Pd/g-C3N4(105 mV at 10 mA cm2 and 69 mV.dec−1) and Pd/CB(117 mV at 10 mA cm2 and 68 mV.dec−1). The impedance spectroscopy study shows Pd-Ni/g-C3N4 demonstrated the smallest semicircle. Further, the Chronoamparometry(CP) and linear sweep voltammetry (LSV) stability study of the highest performing electrocatalyst demonstrates negligible loss in current density for 12 h and minor change in the polarization curve after10,000 cycles. This study shows how the support material influences noble metal catalysts’ activity and stability via the support- metal interactions.