Preparation Of FeWO₄-based Naon-composites And Its Performance For Oxygen Evolution Reaction

Hydrogen is an ideal renewable energy source with clean and energy-efficient properties.Water splitting is an efficient technology for hydrogen production,but the complex four-electron process of the anodic oxygen evolution reaction（OER）leads to slow reaction kinetics,which limits the efficiency of overall water splitting.Noble metal-based（such as Ir-and Ru-based）catalysts show decent catalytic activity for OER,but the low reserves and high cost limit its large-scale applications.Therefore,exploring cost-effective and high-performance non-noble metal OER catalysts is an urgent task for the development of water splitting.Recently,Fe WO₄ with the excellent electrochemical properties have broad application prospects in the fields of supercapacitors,sensors,batteries,and catalysis.Therefore,it is important to construct Fe WO₄ materials,and explore the relationship between their properties and performance.In this thesis,the Fe WO₄-based nanocomposite catalysts with different morphologies and compositions are synthesized by introducing other effective components,constructing heterostructure,and adjusting the morphology.The OER performance of the catalysts is also investigated.The main content and conclusion are as follows:（1）The Fe WO₄-WO₃ catalyst with heterostructure（Fe WO₄-WO₃/NF）is developed by the combination of solvothermal and high-temperature calcination.The nanointerface between different components of WO₃ and Fe WO₄ can be observed by TEM.And the shift of binding energy confirmed by XPS further proves the existence of heterostructure.The electrochemical characterization in alkaline media（1.0 M KOH）shows that it only needs the overpotential of 200m V to reach 10 m A cm^-2,and it can work stably for 100 h at the large current density of 1000 m A cm^-2.The great performance can be attributed to the WO₃modified Fe WO₄,which promotes the intrinsic activity of the sample,and the formation of heterostructure could enhance the electron transfer efficiency,resulting in good OER performance.（2）The carbon encapsulated Fe WO₄-Ni₃S₂ catalyst with 3D spherical flower-like nanosheets（Fe WO₄-Ni₃S₂@C/NF）is prepared by introducing the carbon layer to encapsulate the surface of the catalyst.The 3D spherical flower nanosheets morphology of Fe WO₄-Ni₃S₂@C can be confirmed by SEM.And the existence of carbon-encapsulated structures can be observed by TEM.Fe WO₄-Ni₃S₂@C/NF exhibits excellent performance towards OER,which only needs the overpotential of 200 m V at 10 m A cm^-2.Furthermore,it possesses decent stability for working continuously 100 h at 1000 m A cm^-2,which suggests satisfactory stability.This good performance could be originated as follows:The 3D spherical flower nanosheets morphology provides a large specific surface area,which helps the catalyst fully contact with the electrolyte;The carbon-encapsulated structure can avoid the direct contact between the metal and the electrolyte,thus optimize the stability of the catalyst.（3）The Fe Ni₃ decorated wolframite Fe WO₄ catalyst（Fe WO₄-Fe Ni₃/NF）with heterostructure and nanosheets arrays is prepared by the construction of heterostructure strategy.The morphology of the nanosheets is characterized by SEM,and the clear nanointerface between Fe Ni₃ nanoparticles and Fe WO₄nanosheets can be confirmed by TEM.XPS characterization show that the existence of heterostructure leads to the change of the electronic structure of the catalyst.The catalyst only needs the overpotential of 200 m V at 10 m A cm^-2,and it can remain for 153 h at 1000 m A cm^-2 with negligible performance degradation.The good performance could be due to:The large specific surface area provided by the nanosheets arrays,which is conducive to the diffusion of products;The modification of Fe WO₄ by Fe Ni₃ alloy leads to great intrinsic activity,and the heterostructure facilitates the rapid transfer of electrons.