Electrocatalytic hydrogen production by bulk and nano Fe2O3 and carbon nanotube modified with Fe2O3

•Fe2O3 in bulk, nanosize and its composite with carbon nanotubes was prepared from iron sludge.•These materials were used as HER electrocatalyst in carbon paste electrode.•The main parameters (pH, catalyst and binder) was optimized for each electrocatalyst.•Carbon paste electrode modified with Fe2O3–CNT showed superior electrocatalytic activity.•Applying successive cyclic sweep potentials caused improvement of HER performance.

Industrial iron sludge was used for the production of bulk Fe2O3, Fe2O3 nanoparticles and Fe2O3–carbon nanotube composite (Fe2O3–CNT) by using hydrothermal method. The structure and morphology of the catalysts were studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) methods. Iron compounds were used as catalysts to modify the carbon paste electrode (CPE). The electro catalytic performance, kinetic parameters and mechanistic studies for hydrogen evolution reaction (HER) on the modified electrodes were investigated by linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) electrochemical techniques. For each of the catalysts, the effect of important parameters such as catalyst and binder amounts in the electrode composition and pH were examined. For all of the modified electrodes, H2SO4 (2 M) solution had the best efficiency. The electrocatalytic activity at the optimum conditions of all the modified electrodes was in the order of Fe2O3–CNT > nano-Fe2O3 > bulk Fe2O3. The modified electrodes were resistive to passivation, and applying successive potential cycles on these electrodes improves the HER performance. Due to the low cost, simplicity, ease of preparation in a large scale and high performance, the electrodes could be promising cathodes for HER in acidic media.

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