Core-shell structured tungstocuprate@silver homobenzotrizoate complex for supercapacitor and oxygen evolution reaction

It remains challenging to develop an efficient and inexpensive polyoxometalate (POM)-based MOFs (POMOFs) electrode material for supercapacitors and electrocatalytic oxygen evolution reaction to achieve efficient bifunctional performance. Herein, for the first time, the core-shell structured tungstocuprate@silver homo-benzotrizoate (Ag6[CuW12O40]@[{Ag(H2btc)}{Ag2(Hbtc)}]n) (shortened as HRBNU-1, where [{Ag(H2btc)} {Ag2(Hbtc)}]n is shortened as Ag-BTC, H3btc = 1,3,5-benzenetricarboxylic acid) complex with copper as het-eroatom was successfully synthesized using simple one-step solution method. The synergistic effect of this unique core-shell structure between Ag6[CuW12O40] and Ag-BTC can facilitate the interfacial electron transport on HRBNU-1. In a three-electrode system, the specific capacitance of HRBNU-1 is 533.6 F g-1 at 1 A g-1 with nickel foam as the collector, and higher than both precursors and as reported in the literature. Initial capacitance is retained at 92.4 % after 5000 cycles. The power density and energy density of the symmetrical supercapacitor assembled with nickel foam as collector are 474.7 W kg-1 and 35.7 Wh kg-1, respectively, at a voltage window of 1.0 V. Meanwhile, in the electrolyte solution of 1 M KOH, the oxygen evolution reaction overpotential is 235 mV at 10 mA cm-2 and a Tafel slope of 76 mV dec-1. Furthermore, compared with the traditional noble metal electrocatalyst, the prepared core-shell structured HRBNU-1 catalyst has good durability and catalytic activity. May be due to the central copper atom and tungsten of Ag6[CuW12O40] form a trimetal synergistic interaction with Ag+ in Ag-BTC through MMIDLINE HORIZONTAL ELLIPSISO bond, which enhances the catalytic activity of the metal active site. This work opens a new way for the application of POMOF in supercapacitors and electrocatalytic oxygen evolution reactions.