Study Of Electrocatalysts For Hydrogen Evolution Reaction

Successful development of low cost, efficient electrocatalysts will be critical to the development of hydrogen production (or hydrogen evolution) technology. Here we report some methods of electrocatalysts preparation for hydrogen evolution reaction (HER).Ni-S alloy electrodes were prepared by pulse plating from a modified Watts bath with thiourea (TU) into the bath. The electrocatalysis activity was learned by cathode polarization curves. X-Ray Diffraction (XRD) and EDXRF methods determined the strutures and composition, respectively. The crystal configuration and particle sizes were also studied by XRD. The results indicated that exchange current density of Ni-S alloy pulse-plated much higher than other electrodes prepared by direct current deposition, and the Ni-S alloy electrodes pulse-plated shows much higher critical configuration and smaller particle sizes. It determined that Ni-S alloy electrodes pulse-plated shows much higher electrochemical catalytic activity and stability.Foam Ni-WC catalyst has been prepared by using the direct chemical reduction and intermittent microwave heating (IMH) methods. The morphology, crystal structure and the composition of the catalyst are characterized by XRD, SEM and TEM. The results show that the overpotential for hydrogen evolution reaction on foam Ni-WC catalyst is 60mV lower than that on pure foam Ni catalyst. The concentration of the electrolyte and the temperature are critical for the catalytic performance of the foam Ni-WC catalyst.A tungsten carbide nanocrystal promoted Pt-WC/C electrocatalyst for the HER for the first time. The results show that the novel electrocatalyst significantly increases the activity for the HER compared to the Pt/C. By comparing the overpotential at 800 mA cm-2, we found that there is a 60 mV reduction on an electrode of 120μgPt-120μgWC/C compared to an electrode of 240μgPt/C. Lower Pt loading can be used by using the novel electrocatalyst along with the enhanced activity. The even better performance can be achieved by increasing the acid concentration and the operating temperature. Kinetic study showed that the HER on the novel electrocatalyst gave higher exchange current density and lower reaction activation free energy than that of the Pt/C electrocatalyst, leading to a lower overpotential and facile kinetics.In addition, Pt was modified by palladium (Pd) over a novel support of tungsten carbide nanocrystals (the catalyst denotes as PtPd-WC/C) by using an IMH method. The as-prepared electrocatalysts was characterized by using the techniques of XRD, SEM, TEM, linear sweeping voltammerty and tested for the HER in the acidic media. It can also be found that a better performance of the HER on PtPd-WC/C electrocatalyst than that on Pt-WC/C electrocatalyst. These effects on the catalytic activity by changing environmental temperature and electrolyte concentration were taken into account. Kinetic study showed that the HER on the PtPd-WC/C electrocatalyst gave higher exchange current density in H2SO4 solution with high concentration, leading to a lower overpotential and facile kinetics. XRD, SEM and TEM images of PtPd-WC/C showed the crystalline features of Pt, Pd and tungsten carbides and indicated the coexistence of these components.