Enhanced proton conductivity and overall water splitting efficiency of dye@MOF by post-modification of MOF

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Herein, dye@MOF composite was prepared by the encapsulation of 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS) into the pores of metal-organic framework (MOF). Firstly, the proton conductivities (σ) of MOF and dye@MOF were evaluated, the σ value of dye@MOF is 10 times that of MOF at 100 ​°C, which indicates dye@MOF has excellent proton conduction capacity. Secondly, MOF and dye@MOF show excellent catalytic performances for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline medium, that is, when the current density is 10 ​mA•cm−2, the overpotentials of MOF and dye@MOF are 225 ​mV and 194 ​mV for OER, and 511 ​mV and 497 ​mV for HER, respectively. Moreover, an asymmetric electrolyzer of dye@MOF/nickel foam (NF)||dye@MOF/NF was assembled to assess the efficiency of dye@MOF for overall water splitting, the result shows that the current density of dye@MOF is 35 ​mA•cm−2 at 1.98 ​V, which exceeds that of MOF-based electrode. The excellent catalytic activity and enhanced proton conductivity of dye@MOF is mainly attributed to encapsulating dye molecules into the channels of MOF. In view of superior catalytic activity and excellent stability, dye@MOF is expected to be a bifunctional electrocatalyst for HER and OER.