Bi-metallic [Cu/Co(6mna) 2 ] n metal organic chalcogenolate frameworks as high-performance electro-catalysts for dye-sensitized solar cells: a ligand-assisted bottom-up synthesis

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 12; no. 3; pp. 1595 - 1608
• Main Authors: Lai, Chun-Wei, Lee, Yu-Chien, Jiang, Yi-Zhen, Lin, Chia-Her, Kumar, Gautam, Huang, Michael H., Li, Chun-Ting
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 16.01.2024
• Subjects: Additives; Carbon; Carbon dioxide; Catalysts; Charge transfer; Cloth; Copper; Dye-sensitized solar cells; Dyes; Electrochemical analysis; Electrochemistry; Electrodes; Iodides; Ligands; Metal-organic frameworks; Porosity; Solar cells; Substrates; Synergistic effect; Synthesis
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/D3TA04970A

Mercaptonicotinate-based metal organic chalcogenolate frameworks (MOFs), including [Cu 2 (6mna)(6mn)NH 4 ] n -NO 3 , [Co 2 (6mna) 2 ] n -NO 3 , [Co 2 (6mna) 2 ] n -Cl, [Cu/Co(6mna) 2 ] n -NO 3 , and [Cu/Co(6mna) 2 ] n -Cl (6mna = 6-mercaptonicotinic acid; 6mn = 6-mercaptonicotinate), were newly introduced as the electro-catalytic counter electrodes in dye-sensitized solar cells (DSSCs). By using a ligand-assisted bottom-up synthesis, these five types of MOF films were covalently bonded to a conducting substrate to deliver their intrinsic electro-catalytic ability without any additives. The DSSCs coupled with all the carbon cloth/MOF electrodes showed a superior solar-to-electricity conversion efficiency (9.4%–10.0%) to the cell with a traditional carbon cloth/Pt electrode (9.3%), demonstrating their outstanding electrochemical activities. Heterogeneous bi-metallic MOFs, [Cu/Co(6mna) 2 ] n -NO 3 and [Cu/Co(6mna) 2 ] n -Cl, outperformed their mono-metallic counterparts by increasing film roughness/porosity and decreasing the activation energy for I − /I 3 − . Their remarkable electrochemical performance was attributed to the successful synergistic effect, where [Cu 2 (6mna)(6mn)NH 4 ] n -NO 3 provided facile charge transfer via its 2D (–Cu–S–) n planes, while [Co 2 (6mna) 2 ] n supplied large surface area and multiple electro-catalytic active sites through its helical (–Co–S–) n chains. With the use of different redox mediators (iodide, Co-phenanthroline, and Cu-neocuproine), the optimal carbon cloth/[Cu/Co(6mna) 2 ] n -Cl electrode also showed better electro-catalytic ability and long-term stability than carbon cloth/Pt. Under room light illumination, higher cell efficiencies were obtained at 1.0 klux (19.5% for an office), 3.0 klux (23.3% for a shopping window), and 6.0 klux (26.4% for a lampshade), revealing the potential of mercaptonicotinate-based bi-metallic MOFs to be applied in various electrochemical devices.