Enhanced catalytic activity of ppy-coated pencil electrode in the presence of chitosan and Au nanoparticles for hydrogen evolution reaction

Catalytically active and low-cost electrocatalysts for the production of hydrogen from water are extremely important for future renewable energy systems. Here, we report the fabrication of a facile pencil graphite electrode modified with polypyrrole-chitosan/Au nanoparticles and tested its performance for electrocatalytic hydrogen evolution reaction (HER) as a model process. The porous surface of the pencil graphite electrode (PGE) was modified potentiostically by polypyrrole (PPy) at various film thicknesses in the presence of chitosan (Chi), which is a natural biopolymer, in the electrolyte medium. After the optimum film thickness had been obtained, the Au particles electrodeposited on to the PPy/Chi composite film at the nano-scale to benefit both from its well-known high catalytic activity and to reduce the amount of precious metal Au to prepare a low-cost eletrocatalyst. The performance of this composite catalyst on the H+ reduction (H-ad formation) and thereby on the hydrogen evolution was investigated. Data from cyclic voltammetry (CV), Tafel polarization curves, and electrochemical impedance spectroscopy (EIS) demonstrated that the current densities related to the electron transfer rate changed with the thickness of the composite film, and the catalytic activity was enhanced more with deposition small amount of Au on to the catalyst surface.