Catalytic Performance Of Tantalum-based Bimetal Oxides (MTa_xO_y) Prepared By A Co-precipitation Method As Counter Electrodes In Dye-sensitized Solar Cells

Rapidly growing energy demands have facilitated the development of solar cells.Dye-sensitized solar cells（DSSCs）as a most cost-effective and high-efficiency device for reasonable use of solar energy has aroused extensive research.Counter electrodes（CEs）play an extremely indispensable role in DSSC,harvesting electrons from the external circuit and catalyzing the triiodide convertion to iodide in the electrolyte.Commonly platinum（Pt）electrode materials have many defects such as high price,scarce reserves and poor durability,which immensely impedes widespread applications in DSSCs.Hence,there is an urgency to develop a cost-effective,highly efficient,stable counter electrode material to replace the traditional platinum electrodes.In this work,we successfully prepared three tantalum（Ta）-based bimetal oxides（NiTa₂O₆,MnTa₂O₆,and AlTa O₄）with good crystallinity via a facile and universal co-precipitation strategy.The electrocatalytic activity and photovoltaic performance of the DSSCs were systematically studied.The results present that the electrocatalyst composed of NiTa₂O₆,MnTa₂O₆,and AlTa O₄ possess excellent triiodide reduction ability and satisfactory electrochemical stability,and the corresponding DSSCs exhibit outstanding PCE of 3.39%,3.28%,and 3.66%,respectively.To further optimize the performance of the counter electrode material,three tantalum-based bimetallic oxides were embedded in the honeycomb biomass carbon（HBC）framework to form a composite material.The introduction of carbon materials can effectively alleviate the nanoparticle aggregation and reduce its size.Besides,the HBC framework with unique honeycomb-like network structure serves as a support material in nanohybrids that can provide numerous fast channels for electron transport and electrolyte diffusion.Benefiting from nanohybrids adequately utilizing the synergistic effects of different components,NiTa₂O₆/HBC,MnTa₂O₆/HBC,and AlTa O₄/HBC present satisfactory charge-transfer resistance(the R_ct value is 1.61Ωcm²,1.19Ωcm²,0.72Ωcm²,respectively).Meanwhile,the electrocatalytic properties of nanohybrids are markedly boosted and exhibit robust corrosion resistance.The photovoltaic devices fabricated with NiTa₂O₆/HBC,MnTa₂O₆/HBC,and AlTa O₄/HBC counter electrode catalysts demonstrate the brilliant power conversion efficiency（PCE）of 7.09%,7.39%,and 7.86%respectively,outperforming the Pt-based cells（6.80%）.Finally,the catalytic performences ofTa-based bimetal oxides and their nanocomposites were explored in a novel system based on D35 dye and Cu⁺/Cu²⁺electrolyte.The photovoltaic properties of NiTa₂O₆/HBC,MnTa₂O₆/HBC and AlTa O₄/HBC were better than their correspondingTa-based bimetal oxides.The DSSCs assembled from NiTa₂O₆/HBC,MnTa₂O₆/HBC,and AlTa O₄/HBC yielded PCEs of2.67%,3.06%,and 3.14%in respectively,in the D35 dye and Cu⁺/Cu²⁺electrolyte system,which are close to Pt CE（2.93%）under the same conditions.This work may launch a novel avenue for the constant reinvention and optimization of energy collection/conversion technologies in the future.