Preparation And Catalytic Properties Of Tungsten-based Bimetal Oxides In Dye-sensitized Solar Cells

Dye-sensitized solar cells（DSSCs）have the advantages of low-cost and high theoretical power conversion efficiency（PCE）.Counter electrode（CE）is an essential component in DSSCs.Platinum（Pt）is the most useful CE material because of its excellent electrocatalytic activity and conductivity toward the reduction of I₃^-.However,it has the disadvantages of high cost,scarce availability,and vulnerability to I^-/I₃^-electrolyte corrosion.Therefore,there is an urgent need to explore a non-platinum counter electrode that is inexpensive,stable,and excellent in performance.Mn WO₄,Zn WO₄,and Cu WO₄ were successfully prepared as counter electrodes of DSSCs using ammonium paratungstate as a precursor and a"two-step method"using hydrothermal reaction combined with heat treatment,and then tested its catalytic performance.The results show that the DSSCs assembled by three tungsten-based oxide counter electrodes obtained 4.17%,4.23%,and 3.53%of PCE in the I₃^-/I^-system electrolyte.Aloe peel waste was used as a carbon source to prepare biomass-derived carbon material composite tungsten-based bimetal oxides（Mn WO₄/BC,Zn WO₄/BC,and Cu WO₄/BC）and used them as counter electrodes.The introduction of biomass-derived carbon reduces the agglomeration of tungsten-based bimetal oxides.At the same time,biomass-derived carbon as a structure directing agent,which makes Mn WO₄ to form a spindle-like nanostructure from a spherical structure.The electrocatalytic activities of Mn WO₄/BC,Zn WO₄/BC,and Cu WO₄/BC were optimized.Among them,the PCEs of Mn WO₄/BC and Zn WO₄/BC CEs of DSSCs reached to 7.33%and 7.61%,which were higher than that of Pt CE（7.04%）.Cu WO₄/BC-based CE also achieved a PCE of 6.52%.The introduction of biomass-derived carbon optimizes the catalytic activity of tungsten-based bimetal oxides,which is attributed to the synergistic effect between tungsten-based bimetal oxides and biomass-derived carbon.The tungsten-based bimetal oxides and their composites were further applied to D35 dye and Cu⁺/Cu²⁺system electrolytes to test their electrocatalytic performance.The results showed that the electrocatalytic activity of Mn WO₄/BC,Zn WO₄/BC,and Cu WO₄/BC was better than Mn WO₄,Zn WO₄ and Cu WO₄.Mn WO₄/BC,Zn WO₄/BC,and Cu WO₄/BC electrode assembled DSSCs obtained PCE of 3.06%,3.57%,and2.77%in this system,which is close to or even higher than Pt（3.12%）PCE in DSSCs assembly.Because the tungsten-based bimetal oxide composite biomass-derived carbon has excellent electrocatalytic performance as a counter electrode catalyst,it is promising alternatives to Pt-based catalysts for DSSCs counter electrode.This also provides a basis for the subsequent research on tungsten-based bimetal compounds.