Preparation Of Molybdenum-based Compounds And Their Application As Catalysts In Dye-sensitized Solar Cells

Dye-sensitized solar cells（DSSCs）are low-cost,easy to prepare and can achieve high power conversion efficiency（PCE）.Counter electrode（CE）,as one of the important components of DSSCs,the catalytic reaction rate of the reduction for I₃^-on the its surface and the conductivity of it greatly influence the PCE of DSSCs.In this study,molybdenum-based compounds were prepared,and their application to DSSCs was investigated.MoO₂,Mo O₃,and Mo O₂@Mo O₃ were synthesized via a two-step method by using Mo Cl₅as a precursor with controlled addition of Ni（NO₃）₂·3H₂O,hydrothermal treatment at 200^oC for 12 h,and annealing at 500 ^oC.The charge-transfer resistance(R_ct)of Mo O₂@Mo O₃ was 6.68Ωcm²,which was superior to that of Pt（10.07Ωcm²）.The short-circuit current densities(J_sc)of the three compounds（Mo O₂,Mo O₃,and Mo O₂@Mo O₃）were determined to be 17.15,15.50 and 18.09 m A cm^-2 and the PCEs of7.29%,8.06%and 7.01%.These values were superior to those of the Pt CE(13.14 m A cm^-2,6.46%)under the same conditions.Mo₂C/MC,Bi/Mo₂C/MC,and Mo C/Mo₂C/MC were prepared via soft-template synthesis at 800^oC using Fe（NO₃）₂·9H₂O,Bi（NO₃）₂·5H₂O,Ni（NO₃）₂·3H₂O,and Na₂Mo O₄ as precursors,phenol and formaldehyde as carbon precursors,and acetic acid as the p H regulator.These molybdenum compounds exhibited good electrocatalytic activity,achieving R_ct values of 6.63,4.73,and 8.64Ωcm²,respectively,all of which were superior to that of Pt（10.07Ωcm²）.The corresponding DSSCs with Mo₂C/MC,Bi/Mo₂C/MC,and Mo C/Mo₂C/MC as the CE materials showed J_sc values of 17.10,18.11,and 15.13 m A cm^-2,and PCEs of 7.29,8.06,and 7.01%,respectively,which were superior to those of the Pt CE(13.14 m A cm^-2 and 6.46%)under the same conditions.Using Fe（NO₃）₃·9H₂O,Bi（NO₃）₃·5H₂O,Co（NO₃）₂·6H₂O,and Na₂Mo O₄ as precursors,Fe Mo O₄,Bi₂Mo O₆,and Co Mo O₄ were prepared via the hydrothermal method at 200,60,and 180^oC,respectively.Fe Mo O₄ exhibited good electrocatalytic activity and an R_ct of 36.53Ωcm².The DSSC with Fe Mo O₄ as the CE material showed a J_sc of 15.77 m A cm^-2 and PCE of 5.87%,which were comparable to those of the Pt CE(13.14 m A cm^-2,6.46%)under the same conditions.The prepared molybdenum-based compounds exhibited excellent electrocatalytic activity when used in DSSCs,and their electrocatalytic activities and PCEs were comparable to those of Pt.The prepared materials provide broad development prospects for the commercial application of DSSCs.