Preparation And Electrocatalytic Performance Of W₁₈O₄₉ Based Self-Supported Electrode Materials

Designing efficient and cheap electrocatalyst is important for the preparation of renewable energy.W18O49 based electrocatalytic materials have the potential for hydrogen and oxygen evolution,and are expected to be bifunctional electrocatalysts.But in practical application,the low conductivity limits the improvement of electrocatalytic activity.In addition,there are few reports on whether W18O49 based electrocatalytic materials will be transformed into other species during electrocatalytic reaction,and the electrocatalytic mechanism is still unclear.In this paper,highly efficient W18O49 based self-supported electrocatalytic materials were designed by doping and heterojunction construction.The electrocatalytic mechanism was explored in detail.The main achievements are as follows:(1)The Ni-doped W18O49/NF catalyst with abundant active sites was obtained by a solvothermal-low temperature pyrolysis process.The Ni-doped W18O49/NF underwent self-reconstruction during electrochemical activation.The nature of electrochemical activation was systematically explored.The Ni-doped W18O49/NF catalyst was reconstructed into activated AM/NiWOx/NiOOH/NF.Due to the strong interaction between non-3d W and 3d Ni ions,the enriched active sites,the increase of amorphous interfaces and the improvement of oxidation/reduction capability,the reconstructed AM/NiWOx/NiOOH/NF showed higher catalytic activity than the Ni-doped W18O49/NF.(2)The Fe,Ni-codoped W18O49/NF was synthesized by solvothermal method.The introduction of Fe ions strenghted the interaction between electrons and promoted the formation of Fe3+/Ni3+ ions and W4+ ions.The unsaturated W=O bond increases with the increase of W4+ ions,which can effectively improve the adsorption of intermediate products in HER,and thus enhance the adsorption capacity of water molecules.The Fe3+/Ni3+ ions as OER active sites show strong orbital overlap with the reaction intermediates.At the same time,the Fe,Ni-codoped W18O49/NF electrocatalyst exhibits enriched active sites,fast electron transfer efficiency,increased electrochemical active area and modulated potential of the valence/conduction band,thus improving the electrocatalytic activity.(3)The heterogeneous W18O49/NiWO4/NF electrocatalytic material was successfully prepared by multi-step synthesis strategy.The heterogeneous electrocatalyst showed different reconstruction in HER and OER.The hydrogen/oxygen evolution process makes W18O49 tend to be amorphous.The interface formed by the heterogeneous structure further accelerates the interaction between electrons during the reconstruction process,promoting the formation of crystallization-amorphous active interface and active sites.The reconstructed H-AM/NiWO4/NF and O-AM/NiWO4/NiOOH/NF show excellent electrocatalytic activity and stability.(4)The Act-CoOOH/W18O49/NF was prepared via a solvothermal-in situ electrochemical activation process.The in situ transformation induced the amorphous of W18O49,effectively changed the interfacial interaction and redistributed electrons on the heterogeneous interface.The Co3+/Ni3+(especially for Co3+)ions and OER reaction intermediate exhibit strong orbital overlap through orbital interaction.The low coordination W4+ions promoted the generation of oxygen vacancies and enhanced the adsorption of water.Additionally,the electrochemical reconstruction optimizes the flat band potential to achieve high intrinsic HER activity.(5)A variety of tungsten oxide based electrocatalytic materials were synthesized on copper foam by different method.It was found that the W4+ions were crucial to improve the electrocatalytic stability.By adjusting the process,Ni-doped CuO·3H2O/W18O49/CF with high catalytic activity and stability was prepared.The doping of Ni ions drives the strong interaction between the heterojunction,effectively improves the electron transfer at the interface,increases the oxygen vacancies,and improves the adsorption capacity of water molecules.