One-step electrodeposition of chitosan/phosphonate iron(III) hybrids film and its pH-controlled switchable electrocatalytic behavior

The switchable/tunable electrocatalysis is of great importance in both fundamental and application research. In this work, we synthesize the CS−Fe(notpH3) hybrids film by the simple one-step electrodeposition technique (CS: chitosan; Fe(notpH3): 1,4,7-triazacyclononane-1,4,7-triyl-tris methylene-phosphonic acid iron(III) complex). The stable immobilization of Fe(notpH3) in CS polymer originates from the strong electrostatic and/or hydrogen bonding interactions between Fe(notpH3) and CS, which also enhances the insolubility of CS in acidic solution. The immobilized Fe(notpH3) complex undergoes an effective direct electron transfer reaction and shows a particular pH-sensitive electrochemical property. Based on the particular formal potential hopping mechanism of Fe(notpH3) complex, the CS–Fe(notpH3) hybrids film can be further used to realize pH-controlled switchable electrocatalysis toward H2O2 reduction.