Design of a novel “ON-OFF” switchable enzymatic biofuel cell based on pH-sensitive PS-b-P4VP diblock copolymer

A novel enzymatic biofuel cell (EBFC) mediated by pH change of solution has been designed with an amphiphilic polystyrene-block-poly(4-vinylpyrdine) (PS-b-P4VP) as “ON” and “OFF” switch and laponite-supported enzyme hybrids as biocatalyst. The bioanode and biocathode were successfully established by sequential assembly of PS-b-P4VP and laponite-supported glucose oxidase or laccase on glassy carbon electrode, respectively. Consecutively switching of the solution pH below and above the pKa of P4VP, the reversible electrostatic interaction transformation between repulsion and attraction of PS-b-P4VP toward electrochemical probe was realized to control the “ON” and “OFF” behavior of EBFC. When the pH of reaction solution below the pKa (such as pH 4.5), the protonated copolymer could allow negatively charged probe access to the catalytic centers of enzymes, leading to the enhanced electrochemical reaction and electron transfer of EBFC (set as “ON” state); Above the pKa (such as pH 7.0), the cell reaction was blocked because the lone pair electron of pyridine unites resulted from PS-b-P4VP could effectively inhibit the reactant transmission of electrochemical probe (set as “OFF” state). The developed EBFC exhibited an obvious “ON-OFF” switching property at both pH values. At “ON” state, the open circuit potential (Ecellocp) and maximal power output density (Pmax-ON) reached to 0.42 V and 3.49 μW cm−2, while at “OFF” state, the corresponding Ecellocp and Pmax-OFF were only 0.22 V and 0.39 μW cm−2. Moreover, this rapidly repeated switching behavior could open an alternative way for the fabrication of tunable EBFC, and showed great prospect in biomedical field.