Preparation Of Molybdenum-based Bimetallic Oxide MMo_xO_y By Chemical Co-precipitation And Catalytic Performance Of MMo_xO_y As Electrocatalysts In Dye-Sensitized Solar Cells And Hydrogen Evolution

Dye-sensitized solar cells（DSSCs）and water splitting for hydrogen evolution equipments have attracted considerable attention due to the merits of simple process,environment friendly,and low cost.Electrocatalytic materials are essential components in DSSCs and hydrogen evolution equipments.The noble metal,Pt and Pt/C are widely used in electrocatalytic materials,but scarcity and high price limit its large-scale application.In this regard,it is great of importance to design high-performance and low-cost electrocatalytic materials for the commercial application of DSSCs and water splitting for hydrogen evolution equipments.First,three kinds of molybdenum（Mo）-based bimetallic oxides（ZnMoO₄,Cu₃Mo₂O₉ and MnMoO₄）were prepared by a simple chemical co-precipitation method and used as counter electrode（CE）catalysts in DSSCs.Mo-based bimetallic oxide catalysts exhibited poor electrocatalytic activities in I₃^-/I^-electrolyte.The power conversion efficiency（PCE）of DSSCs assembled with ZnMoO₄,Cu₃Mo₂O₉ and MnMoO₄ CEs was 2.47%,2.39%and 2.23%,respectively.Second,three kinds of three-dimensional aloe waste-derived carbon（3D-AWC）supported Mo-based bimetallic oxide composites（ZnMoO₄/3D-AWC,Cu₃Mo₂O₉/3D-AWC and MnMoO₄/3D-AWC）were successfully prepared by chemical co-precipitation method and used as CE catalysts in DSSCs.3D-AWC-supported Mo-based bimetallic oxide composites exhibited excellent electrocatalytic activity and stability.The DSSCs assembled with ZnMoO₄/3D-AWC,Cu₃Mo₂O₉/3D-AWC and MnMoO₄/3D-AWC CE catalysts obtained high PCE of 7.65%,7.33%and 6.92%,respectively,higher than that asswmbled with Pt（6.74%）.The excellent catalytic performance of the 3D-AWC-supported Mo-based bimetallic oxide composites can be attributed to the synergistic effect between 3D-AWC and Mo-based bimetallic oxide.Furthermore,the catalytic properties of Mo-based bimetallic oxides and their composites were investigated in D35 dye and Cu⁺/Cu²⁺electrolyte system.Compared to the Mo-based bimetallic oxides,the 3D-AWC-supported Mo-based bimetallic oxide composite catalysts exhibited superior electrocatalytic activities.ZnMoO₄/3D-AWC,Cu₃Mo₂O₉/3D-AWC and MnMoO₄/3D-AWC CE catalysts delivered low R_ct of 3.38Ωcm²,8.21Ωcm² and 9.15Ωcm²,respectively.In addition,the DSSCs with ZnMoO₄/3D-AWC,Cu₃Mo₂O₉/3D-AWC and MnMoO₄/3D-AWC CEs obtained high PCE of 3.08%,2.79%and 2.75%,respectively,close to that with Pt CE（2.95%）.Final,the 3D-AWC-supported Mo-based bimetallic oxide composites were used as electrode catalytic materials in hydrogen evolution reaction.Compared with those in the0.5 M H₂SO₄ electrolyte,3D-AWC-supported Mo-based bimetallic oxide composites exhibited superior electrocatalytic performance and electrochemical stability in 1.0 M KOH.The ZnMoO₄/3D-AWC,Cu₃Mo₂O₉/3D-AWC and MnMoO₄/3D-AWC electrode delivered Tafel slope of 54 m V dec^-1,76 m V dec^-1,and 105 m V dec^-1,respectively,and overpotential of 124 m V,135 m V,and 156 m V at current density of 10 m A cm^-2,respectively,in 1.0 M KOH.First-principle density functional theory（DFT）calculations revealed the catalytic mechanism of Mo-based bimetallic oxides in DSSCs and hydrogen evolution.First-principle DFT calculations provide a new strategy for understanding the catalytic mechanism of catalytic materials.The method descrbed in this work of introducting biomass-derived carbon to improve catalytic performance can be expected to design and develop more electrode materials in energy devices.