Electrochemical Impedance Spectroscopy Studies on Hydrogen Evolution from Porous Raney Cobalt in Alkaline Solution

The hydrogen economy has gained increasing attention from government bodies and major oil companies. There are proven examples of this technology being implemented in a society like Iceland, where electrolytic hydrogen generation powered by renewable energy has been developed to support the demand of the transportation sector. Hydrogen generation via electrolysis consists of the hydrogen and oxygen evolution reactions. Conventional electrode materials used for the electrolysis belong to the platinum group metals that are expensive. In this work, Raney cobalt as an alternative which is inexpensive, electrodeposited from a Watts bath is reported. In addition, modifying the Watts bath composition and combining two types of Raney have also been investigated and reported. We have identified overpotentials of -349 mV for the best Raney cobalt sample and -270 mV when Raney nickel is combined with Raney cobalt for hydrogen evolution in alkaline medium at 100 mA cm(-2). Another objective of this work is resolving the difficulties found in interpreting the electrochemical impedance data for Raney type materials. The nickel binder competes with Raney cobalt during the reaction, these interactions exhibit different impedances. The electrodeposited electrodes have been tested for energy efficiency with overpotential curves and electrochemical impedance measurements. Additional tests including X-ray diffraction and field emission scanning electron microscopy equipped with energy dispersive analysis have also been undertaken that support the results of the catalyst surfaces under study.