原位合成AgSPh有機金屬骨架作為高效能電觸媒應用於銅(I/II)-neocuproine氧化-還原對

Abstract

成功合成了兩種基於銀的金屬有機硫族化物骨架（MOFs）薄膜，即[Ag(6mna)2]n和 [Ag(SePh)2]n（其中6mna = 6-巰基吡啶-3-羧酸; SePh = 苯基硒化物），並將其應用為染料敏化太陽能電池（DSSCs）中對電極的高性能電催化劑。藉由在多孔碳布導電基材（CC）上預錨定不同的自組裝單分子層，如二甲基甲醯胺中的6mna層（6mnaDMF）、去離子水中的6mna層（6mnaDIW）以及去離子水中的苯二硫醇層（BDTDIW），然後將這些碳布基板浸泡於[Ag(6mna)2]n合成的水熱反應中。經過以下長晶機制獲得了三種電極，分別是CC/6mnaDMF/[Ag(6mna)2]n、CC/6mnaDIW/[Ag(6mna)2]n、CC/BDTDIW/[Ag(6mna)2]n。 (i) 在預浸泡溶液中將6mna（或BDT）錨定在碳布表面的羥基，然後巰基的去質子化在錨定6mna（或BDT）層上於MOF前驅物中。 (ii) 銀(I)離子與錨定的6mna (或BDT) 層上的巰基配位。 (iii) MOF前驅物中去質子化的6mna與銀 (I) 配位，形成二維銀硫平面。 (iv) 數個銀硫平面相互堆疊形成三維配位聚合物網絡。這三種[Ag(6mna)2]n電極具有相同的晶體結構，符合文獻中的[Ag(SePh)2]n單晶結構。CC/6mnaDIW/[Ag(6mna)2]n電極具有最佳的電催化活性和最低活化能。當染敏電池使用CR147作為染料、銅(I/II)-2,9-二甲基-1,10-菲囉啉作為氧化-還原對、CC/6mnaDIW/[Ag(6mna)2]n作為對電極，可達到8.52%的光電轉換效率，高於參考的CC/Pt電極 (7.43%)。另一方面，通過熱蒸鍍銀金屬薄膜在碳布上，用二苯基二硒烷和去離子水的化學氣相反應進行[Ag(SePh)2]n薄膜的金屬輔助原位晶體合成。與上述的長晶機制相似獲得與文獻中[Ag(SePh)2]n單晶結構一致的CC/Ag/[Ag(SePh)2]n電極。與CC/Ag和CC/Pt電極相比，[Ag(SePh)2]n的較大顆粒提供相近的電催化活性和較低的活化能。使用CC/Ag/[Ag(SePh)2]n電極的DSSC達到9.43%的效率，高於CC/Pt的效率，顯示其替代昂貴金屬的巨大潛力。

Two-types of silver-based metal-organic chalcogenolate framework (MOFs) thin films, i.e., [Ag(6mna)2]n and [Ag(SePh)2]n (6mna= 6-mercaptopyridine-3-carboxylic acid; SePh= phenylselenide), were successfully synthesized and applied as the high performance electro-catalysts for the counter electrodes in dye-sensitized solar cells (DSSCs). A ligand-assisted bottom-up crystal growth of [Ag(6mna)2]n thin film was performed by the pre-anchoing a self-assemble monolayer of 6mna in dimethylformamide (6mnaDMF), a layer of 6mna in deionic water (6mnaDIW), and a layer of bezene-1,4-dithiol in deionic water (BDTDIW) on a mesoporous carbon cloth (CC) as the conducting substrate, and then by immersing these CC-based substrates into a hydrothermal bath for [Ag(6mna)2]n synthsis in deionic water. Accordingly, three types of [Ag(6mna)2]n were obtained, including CC/6mnaDMF/[Ag(6mna)2]n, CC/6mnaDIW/[Ag(6mna)2]n, and CC/BDTDIW/[Ag(6mna)2]n, respectively, via the following mechanism. (i) Anchoring of 6mna (or BDT) onto the hydroxyl groups on CC in a pre-soaking solution, and then the deprotonation of thiols on the anchoring-6mna (or anchoring-BDT) layer in a MOF precursor. (ii) Coordination of Ag(I) ions to thiols on the anchoring-6mna (or anchoring-BDT) layer. (iii) Coordination of deprotonated 6mna in a MOF precursor to Ag(I) then to form a two-dimensional (2D) –(Ag–S)n– plane. (iv) Stacking among several –(Ag–S)n– planes to afford the three-dimensional (3D) coordination polymer network. These three [Ag(6mna)2]n electrodes exhibited the same crystal structure, referring to the reported [Ag(SPh)2]n single crystal. Among them, the best electro-catalytic activity and the lowest active energy for Cu(I/II)-neocuperine redox shuttle was obtain by the CC/6mnaDIW/[Ag(6mna)2]n electrode due to its most uniform and adhesive film covered by identical rod-like particles. Then the DSSC coupled with CR147 as sensitizer, Cu(I/II)-neocuperine as redox shuttle, and a CC/6mnaDIW/[Ag(6mna)2]n counter electrode reached 8.52%, which surpassed the reference CC/Pt electrode (7.43%). On the other hand, a metal-assisted bottom-up crystal growth of [Ag(SePh)2]n thin film was conducted by depositing an Ag layer on CC via a thermal-evaporation process, and then by treating this CC/Ag electrode with the chemical vapor of diphenyl diselenide and DIW. Accordingly, the CC/Ag/[Ag(SePh)2]n electrode, having the consistent crystal structure to the reported [Ag(SePh)2]n single crystal, was constructed via the similar mechanism mentioned above. In comparison to the CC/Ag and CC/Pt electrodes, the larger particles of [Ag(SePh)2]n would provide a comparable electro-catalytic activity and a lower active energy for Cu(I/II)-neocuperine redox shuttle. Then the DSSC coupled with CC/Ag/[Ag(SePh)2]n electrode reached a hier cell efficiency of 9.43%, than that of the cell with CC/Pt, revealing a great potential to replace expensive metals.