Preparation Of Niobium-based Bimetallic Oxides MNbO₄ By Co-precipitation And Their Catalytic Properties As Electrocatalysts In Dye-Sensitized Solar Cells And Hydrogen Evolution Reaction

Dye-sensitized solar cells（DSSCs）have gradually become a promising solar photovoltaic device owing to their high power conversion efficiency（PCE）,low cost,environmental friendliness,and ease of assembly.A typical DSSC consists of a counter electrode（CE）,a photoanode,and an electrolyte.Pt is the preferred choice for the CE,which plays a dominant role in conducting electrons and catalyzing the I₃^-reduction reaction.However,the extreme scarcity of Pt hinders its use in commercial solar cells.Therefore,it is necessary to explore substitutes for Pt that are cost-effective,highly efficient,and stable.In this work,three kinds of niobium（Nb）-based bimetallic oxides（AlNbO₄,CrNbO₄,and FeNbO₄）were successfully prepared using a simple co-precipitation method and employed as CE catalysts in DSSCs.The electrocatalytic performance of AlNbO₄,CrNbO₄ and FeNbO₄ was poor as compared to that of Pt,with their corresponding DSSCs exhibiting PCEs of 2.65%,2.54%and 2.38%,respectively.Secondly,composites of niobium-based bimetallic oxides with aloe-peel derived biomass carbon（AlNbO₄/APPC,CrNbO₄/APPC,and FeNbO₄/APPC）were also prepared by the co-precipitation method.The combination of the Nb-based bimetallic oxides with biomass derived carbon results in a composite that has excellent catalytic activity and increased conductivity leading to an improved photovoltaic performance of DSSC.The introduced biomass derived porous carbon not only alleviates the agglomeration of oxide nanoparticles,thereby exposing more catalytic active sites,but also provides effective channels for effective electron transport.The DSSCs with AlNbO₄/APPC,CrNbO₄/APPC,and FeNbO₄/APPC as CEs had PCEs of 7.31%,7.09%,and 6.93%,respectively,which were superior to that of Pt electrode（6.84%）under the the same conditions,and was expected to be an alternative material of Pt catalyst.In addition,the electrocatalytic activity of the as-prepared bimetallic oxides and their composites was investigated in the Cu⁺/Cu²⁺electrolyte system.The DSSCs with AlNbO₄/APPC,CrNbO₄/APPC,and FeNbO₄/APPC as CEs,Cu⁺/Cu²⁺as an electrolyte,and D35 dye,exhibited PCEs of 3.94%,3.79%,and 3.59%,respectively,which was better than the PCE obtained with Pt electrode and corresponding Nb-based bimetallic oxide under the same conditions.Thus,these composites have potential application in Cu⁺/Cu²⁺electrolyte and D35 dye system.Futhermore,AlNbO₄/APPC,CrNbO₄/APPC,and FeNbO₄/APPC were used as electrocatalysts for electrochemical hydrogen evolution reaction,which exhibited superior electrocatalytic performance and electrochemical stability in 1 M KOH electrolyte.The overpotential of AlNbO₄/APPC,CrNbO₄/APPC,and FeNbO₄/APPC electrode was 131.6 m V,134.6 m V,and 160.6 m V,respectively,and Tafel slope was 54m V dec^-1,80 m V dec^-1,and 96 m V dec^-1,respectively.