Cobalt Containing Zeolitic Imidazolate Framework Incorporated Electrospun Carbon Nanofibers As Free-Standing Film Sensor for Electrochemical Detection of Hydrogen Peroxide

Hydrogen peroxide (H 2 O 2 ) is used as an oxidizer, bleaching agent and disinfectant in various fields such food processing, medicine and environment remediation. Further, H 2 O 2 is also produced as by-product of biochemical processes in human body. Thus, detecting the trace quantities of H 2 O 2 is of great significance. Among various detection techniques, electrochemical sensing offers relatively simple and fast detection where current signal generated from redox reaction of target analyte corresponds to its concentration. The performance of electrochemical sensors i.e. its sensitivity, lower limit and detection range depends on the type of materials utilized as electrocatalyst. Noble nanoparticles supported by nanocarbons are commonly used due to their higher sensitivity of detection, but their high cost and scarcity limit their widespread use [1]. Among low cost transition metals, cobalt nanoparticles derived from pyrolysis of metal organic framework (ZIF-67) are attractive materials for electrochemical H 2 O 2 sensing having superior properties such as high surface area, regular porous structure and conductive carbon matrix. Various conductive nanocarbon supports can be utilized to uniformly disperse ZIF-67 nanocrystals. Carbon nanofibers owing to low-cost scalable synthesis are ideal candidates for such conductive support. Their 1D structure offers highly conductive pathways for electron transport and they can form hierarchal porous structures with ZIFs where the micropores(<2nm) of ZIF contain active sites for reduction of H 2 O 2 and macropores (>50 nm) created by interconnection of carbon nanofibers minimizes mass transfer resistance of reactants and products to and from active sites. In this work, cobalt-carbon nanocomposites are synthesized by electrospinning of polymer precursor polyacrylonitrile (PAN) solution in dimethylformamide (DMF) solvent in which 30% ZIF-67 was uniformly dispersed. Electrospun polymer film was stabilized in air at 250 o C and carbonized in argon (Ar) at 900 o C to yield cobalt nanoparticles incorporated nitrogen-doped carbon nanofiber (ZIF-67/N-CNF) film. Amperometric tests on glassy carbon electrode (GCE) show that incorporation of ZIF-67 can improve sensitivity of N-CNF upto 3 times to 300 μA/ mM. cm 2 for H 2 O 2 detection. Carbonization of polymer film under 5% H 2 /Ar atmosphere resulted in further improvement of sensitivity to 475 μA/mM.cm 2 . Morphological and chemical properties were characterized to understand structure-property relationships. This sensor also demonstrated good stability and selectivity and was applied to milk and fruit juice samples to show their potential for real applications. ZIF-67/N-CNF film can be used as free standing sensor for H 2 O 2 detection which minimize the complicated steps of ink preparation typically required for powder based electrocatalysts for testing sensing performance on GCE. Further, miniaturized screen-printed electrodes (SPE) modified by ZIF-67/N-CNF, were fabricated as H 2 O 2 sensor to demonstrate low-cost portable detection. Reference: Riaz, Muhammad Adil, et al. "Ultralow-Platinum-Loading Nanocarbon Hybrids for Highly Sensitive Hydrogen Peroxide Detection." Sensors and Actuators B: Chemical (2019), 283, 304-311. (https://doi.org/10.1016/j.snb.2018.12.041)