Preparation Of Iron-based Electrocatalyst And Its OER Performance

With a rising global population,increasing energy demands,and impending climate change,major concerns have been raised over the security of our energy future.Electrochemical energy conversion,especially electrochemical water splitting,has become a research hotspot,but the slow reaction kinetics on seriously limits the conversion rate and efficiency.For this reason,catalysts are usually used to accelerate the reaction kinetics and improve the efficiency.Therefore,it is very important to develop efficient,stable and low-cost electrocatalysts.Therefore,we studied the preparation of iron-based catalysts and the mechanism of oxygen production reaction（OER）.A series of systematic studies were carried out to provide some guidance for the design of catalysts.The main research results are as follows:We have prepared unit iron-based particle catalyst and thin film catalyst by NaBH₄reduction and electrochemical cathodic deposition respectively.The structure characterization shows that the catalyst exists in the state of hydroxyl oxide when the electrode is working.The OER properties on Au,GC,Pt and Pd substrates were investigated.The results showed that the OER properties on gold substrates were the best.The porous heterogeneous catalyst with surface active sites was designed.The results show that the polycrystalline Ni metal skeleton reduced by three-dimensional mesoporous NiO has excellent OER performance when Fe is introduced into its outermost surface.At the same time,during OER reaction,the outer surface of Ni was reconstructed,forming a heterogeneous structure composed of NiFeO_xH_y surface layer and electronic conductive Ni core.The intrinsic activity of the prepared NiFeO_x H_y/Ni catalyst increased with the increase of the number of active centers and the charge conductivity.On the contrary,scattered iron species are the most active sites,which is essentially active.FeW composite oxides were successfully synthesized by hydrothermal method,and FeWO_x H_y catalyst was formed by structural transformation during OER test.The reconstructed FeWO_xH_y catalyst shows excellent OER performance.The overpotential at 10 mA/cm² is 0.38 V,and it also shows excellent stability.Theoretical calculation shows that the iron in the active site improves the conversion of^*OH to^*O in OER process,and thus improves its catalytic activity.A series of Fe_100-xNb_x mixed oxide materials were synthesized by hydrothermal method with oxalic acid,and their OER properties were tested in alkaline solution.At the same time,the reaction steps were studied by theoretical calculation,and the mechanism of high OER activity of Nb doped Fe based catalyst system was obtained.Oxalic acid plays an important role in the preparation of atom level mixed iron niobium composite.Oxalic acid can inhibit the hydrolysis of niobium to form niobium oxide particles and prepare FeC₂O₄ containing niobium.In situ electrochemical reaction,FeC₂O₄ was converted into FeNb homogeneous mixed hydroxide.Fe₉₀Nb₁₀ mixed catalyst has good OER activity and long-term stability on gold substrate.Theoretical calculation shows that Nb substitution promotes the conversion of OH adsorbed on Fe site to O,reducing the potential barrier of total OER reaction,and improving the OER activity significantly.