POM@TM-MOFs prism-structures as a superior bifunctional electrocatalyst for overall water splitting

In order to meet the application needs of electrochemical water splitting, it is extremely important but challenging to develop efficient, cost-effective, long-lasting bifunctional catalysts. Herein, three POM@TM-MOFs composites were synthesized to K6[P2W18O62] encapsulating into TM-BTC (TM = Fe, Co or Ni, BTC = 1,3,5-benzenetricarboxylic acid) by a well-established impregnation method. The TM-MOFs with internal diameters of 16.08 Å and 6.95 Å apertures are largely enclosed by BTC ligands that act as switches that open and close the channel to allow leaching and immersing of POM, which can solve the problem of POM agglomeration and poor stability and maintain the original porous structure of MOFs. POM@Ni-MOF showed excellent bifunctional electrocatalytic performance with overpotentials of 68 mV and Tafel slopes of 77.3 mV/dec for HER, overpotentials of 107.3 mV and Tafel slopes of 61 mV/dec for OER, respectively. More importantly, POM@Ni-MOF/CC∥POM@Ni-MOF/CC was obtained by POM@Ni-MOF for overall water splitting and required a low cell voltage of only 1.51 V at 10 mA cm−2, which is slightly lower than the Pt–C/CC//RuO2–C/CC system.