Preparation Of Polyaniline Composite Transition Metal Catalysts And Their Application In Oxygen Evolution Reaction

Hydrogen has become the desirable clean energy carrier instead of traditional fossil fuels because of its extensive sources,high combustion value,zero-pollutant emission and renewable energy.Hydrogen production by electrical decomposition of water is a promising green technology that can effectively utilize renewable energy and realize energy storage and conversion.The characteristics of clean,large-scale and sustainable hydrogen production make it possible for hydrogen to be commercialized as an efficient and clean energy.Nevertheless,there are some non-ignorable drawbacks,such as high expenditure,large energy consumption and low energy conversion efficiency existing in the process of hydrogen production from electrolytic water.Besides,oxygen evolution reaction（OER）is the rate-determining step of the whole reaction process due to its sluggish kinetics as a consequence of the quadrielectron transfer in the formation of oxygen-oxygen bond.Thus,the fabrication of OER catalyst with high efficiency is the key to realize its industrial application.Polyaniline（PANI）has become the increasing attention in the field of electrocatalytic composites due to its advantages of simple monomer,convenient synthesis,high conductivity and stable chemical properties.In addition,polyaniline molecules contain abundant amino and imino functional groups,which can provide lone pair electrons to coordinate with transition metals,enhance the interaction between polyaniline and hydroxide and metal oxides,and endow the composite with excellent electronic structure and high structural stability.In this contribution,polyaniline composite transition metal oxides and polyaniline composite hydroxides catalysts were designed by electrochemical oxidation method and wet-impregnation method,respectively.Moreover,SEM,TEM,EDS,SAED,XRD and other characterization methods were used to analyze their surface morphologies,compositions,structures and valence states.The OER performance of the corresponding catalysts were evaluated by cyclic voltammetry test,polarization curve test and Tafel curve test and the specific research contents are as follows:1)The M/PANI（M=Fe,Co,Ni,Cu）catalysts were synthesized by electrochemical method using PANI as a substrate.The effects of metal species,component content and conductivity on the catalytic OER performance were systematically investigated.It has been demonstrated that the 20%Co/PANI catalyst exhibits the excellent OER performance.Noticeably,it attained a low overpotential of340 m V at an anodic current density of 10 m A cm^-2 and a small Tafel slope of 59 m V dec^-1 in 1M KOH electrolyte.2)The Co₃O₄/PANI catalysts were prepared by wet-impregnation method and compared with as-synthesized Co₃O₄ and PANI catalysts.The effects of Co loading,conductivity and surface defect sites on the catalytic OER performance were systematically examined.The results showed that 30%Co₃O₄/PANI catalyst exhibited good catalytic activity.More accurately,it gives a low overpotential of 304 m V at an anodic current density of 10 m A cm^-2 and a small Tafel slope of 48 mV dec^-1 in 1M KOH electrolyte.