Preparation Of (Photo) Electrocatalysts Based On Decomposition Of Metal Organic Complexes And Studies On Their Performance Toward Water Splitting

Energy is the material basis of human activities and an important part of sustainable development.Improving energy efficiency and developing new energy are effective ways to solve the current social energy crisis.The oxygen evolution reaction is a core process in various energy conversion and storage devies,such as rechargeable fuel cell,water splitting for hydrogen peoduction and metal-air batteries.Therefore,it is necessary to develop cheap,high efficiency and high selectivity electrocatalyst.This paper constructed three kinds of water oxidation reaction?photo?electrocatalysts,namely Ni?Co?Fe₂O₄/C,NiO-NiS/N-C,and CoP/?-Fe₂O₃ based on the transition metal?Ni,Co,Fe?complex.The morphology,structure and composition of these three?photo?electrocatalysts were characterized.The?photo?electrocatalytic performance of anodic oxygen evolution materials also were detected with the three-electrode system in the electrochemical workstation.The main reaearch contents are as follows:?1?Prussian blue analogues of NiFe and CoFe bimetallic were synthesized by chemical coprecipitation method.NiFe₂O₄/C and CoFe₂O₄/C nanocomposite structure were obtained after pyrolysis in Ar atmosphere.Characterizations showed that the spinel CoFe₂O₄?Ni Fe₂O₄?nanoparticles were uniformly dispersed on the carbon substrate formed in situ.The oxygen evolution activity and stability of NiFe₂O₄/C and CoFe₂O₄/C nanocomposite were measured in 1 M KOH electrolyte.Experimental results showed that NiFe₂O₄/C and CoFe₂O₄/C nanocomposite exhibited good catalytic activity,as evidenced by small onset potential at 1.48 V and 1.51 V vs.RHE,respectively.The electrocatalytic activity of NiFe₂O₄/C did not change significantly after 8 hours stability test at 10 mA cm-2.?2?A Ni-Schiff base complex of vanillin thiosemicarbazone was designed and synthesized as a precursor,and then the NiO-NiS/N-C nanocomposite structure was obtained by annealing the complex mixed with thiourea at high temperature in Ar atmosphere.The XRD,SEM and TEM results showed that NiO and NiS nanoparticles were uniformly dispersed on the nitrogen-doped carbon substrate formed in situ by decomposition of complex.The electrocatalytic activity and stability of NiO-NiS/N-C nanocomposite were measured in 1 M KOH electrolyte.The experimental results showed that NiO-NiS/N-C nanocomposite depicted high electrocatalytic activity with small onset potential at 1.56 V vs.RHE and lower tafel slope?44.7 mV dec-1?.The overpotential required to achieve a current density of 10 mA cm-1 was 374 mV.The catalyst activity remained the same basically after 10 hours stability test at 10 mA cm-2.The results showed that the catalyst had excellent stability in alkaline environment.?3?The ?-Fe₂O₃ nanorod arrays were synthesized by hydrothermal method on conducting glass FTO and then CoP/?-Fe₂O₃ photoanodes were prepared by drop-casting CoP nanoparticles prepared by low-temperature phosphating method?the loading is 0.01 mg cm-2?.The photoelectrocatalytic results showed that the photocurrent density of CoP/?-Fe₂O₃ photoanodes increased by 44%,reaching 0.72 mA cm-2 compared with the original ?-Fe₂O₃ nanorod array at 1.23 V vs.RHE.Electrochemical impedance spectroscopy showed that CoP reduced the charge transfer resistance on the surface of ?-Fe₂O₃,and the Mott-Schottky curve showed that the carrier density of CoP/?-Fe₂O₃ anode was higher than that of ?-Fe₂O₃.CoP deposited on the surface of ?-Fe₂O₃ nanorod arrays,effectively reduced the recombination of electron-hole pairs and accelerated the oxygen evolution reaction at the interface of the semiconductor/catalyst.