Effect of the Chitosan Matrix on the Morphology and Electrocatalytic Activity of Chitosan/Ni Nanocomposite Coatings in Hydrogen Evolution Reaction

In this work, the effect of chitosan concentration in chitosan/nickel composite coatings on their morphology and electrocatalytic activity in hydrogen evolution reaction (HER) was investigated. A series of Chitosan/Ni coatings with chitosan content from 0 to 0.7 wt.% was obtained by nickel electrodeposition onto a preformed biopolymer matrix, enabling targeted control of the roughness and specific surface area of the nickel layers. Morphology and roughness parameters were studied using atomic force microscopy and confocal microscopy. Electrochemical activity in the HER was examined by linear sweep voltammetry. Among the studied electrocatalysts, the Chitosan(0.6)/Ni system showed the best HER efficiency, with an overpotential of −200 mV at a current density of 10 mA/cm2. Electrochemical impedance spectroscopy was used to determine the real surface area of the coatings. The Chitosan(0.6)/Ni sample exhibited the largest surface area, explaining its high HER activity. The obtained data revealed a correlation between chitosan concentration, composite morphology, and electrochemical activity, and allowed determination of the optimal composite composition. The results demonstrate the potential of chitosan as an effective structural modifier of nickel coatings and open up possibilities for the targeted design of composite materials with tailored electrochemical properties.