Lead cathodes functionalized with magnetite particles with enhanced electrocatalytic activity for hydrogen evolution reaction in sulfuric acid solutions

Abstract

The generation of molecular hydrogen through the electrochemical water splitting process has been extensively studied, due to the potential application of hydrogen to produce green energy with fuel cells. Researchers have been focused in the synthesis of electrocatalysts for the hydrogen evolution. The accumulative roll bonding (ARB) is a promising method which can process a large quantity of an electrode for industrial demand. In this research the ARB process is employed to synthesize lead base electrodes functionalized with magnetite particles (Fe3O4) to evaluate their electrocatalytic properties on the hydrogen evolution reaction (HER) in sulfuric acid solutions. SEM, EDS and FESEM techniques are used to characterize the functionalized lead cathodes. The effect of rolling passes, magnetite concentration, and suspended magnetite particles on the HER kinetics is studied using linear voltammetry, Tafel plots, and electrochemical impedance spectroscopy (EIS). The results revealed that lead cathodes functionalized with magnetite present great advantages over lead cathodes, such as: a decrease of 0.37 V in HER over-potential, an increase of 84.3 times in the exchange current density, a decrease in the charge transfer resistance of 98%. From a mechanistic viewpoint, HER is catalyzed by the presence of Fe2+ adsorbed on the lead cathode; ferrous ions are produced from the reductive dissolution of magnetite particles. Long-term electrolysis and multiple cyclic voltammetry tests (800 polarization cycles) revealed that the catalytic effect is maintained during 44 h of operation. According to the Tafel curves and EIS results, the Volmer reaction is the rate determining step of the HER on these functionalized cathodes.