Imine Gels Based on Ferrocene and Porphyrin and Their Electrocatalytic Property.

A series of porphyrin-based imine gels have been synthesized via dynamic covalent gelation between 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin (H2 TAPP) derivatives and various aldehyde compounds. The porphyrin-ferrocene imine gels based on MTAPP (M=H2 , Ni2+ , Co2+ , Pd2+ and Zn2+ ) and ferrocene-1,1'-dicarbaldehyde (NA) display efficient HER, OER and ORR activities in alkaline media. Among the gels, CoTAPP-NA shows an HER current density of 10 mA cm-2 at low overpotential of 470 mV and small Tafel slope of 110 mV decade-1 in alkaline media. CoTAPP-NA also exhibits OER catalytic activity with low overpotential (416 mV for 10 mA cm-2 ). CoTAPP-NA shows ability in overall water splitting in alkaline media. In addition, CoTAPP-NA exhibits onset potential (Ep ) of 0.95 V and half-wave potential (E1/2 ) of 0.84 V in 1.0 mol L-1 KOH solution for oxygen reduction. Moreover, the gel catalyst shows good stability.