Preparation and characterization of nanosized Fe3O4-biochar electrocatalysts with large surface area for H2O2 sensing

Abstract

A nanoscale Fe3O4-biochar (Fe-BC) composite material was prepared using hazelnut shell (HNS) biochar and FeCl2. Biochar was prepared by phosphoric acid (H3PO4)-assisted pyrolysis (BCA) and H3PO4 + microwave (MW)-assisted pyrolysis (BCAMW) of HNS at 500 ◦C. Biochar produced in the presence of H3PO4 exhibited a larger surface area (almost 1300 m2/g) and total pore volume (1.29 cm3/g). Irrespective of activation with MW, Fe3O4 nanoparticles formed on the biochar and its surface area decreased weakly due to iron loading. Based on the temperature- programmed desorption of oxygen (O2-TPD) and temperature-programmed reduction with hydrogen (H2-TPR) results, the reduction of iron and desorption of oxygen from Fe3O4 can be facilitated by the presence of biochar. The estimated crystal size of Fe3O4 could be controlled by pores of biochar. A glassy carbon (GC) electrode coated with Fe-BC was used for the detection of H2O2. The highest H2O2 sensing was measured on Fe-BCAMW having mesoporous structure. After optimization, it was found that H2O2 detection of Fe-BC elec- trocatalysts is linear in the range of 0.5–10 mM. Interference effects of L-cystine, ascorbic acid and urea in H2O2 detection along with detection hydrogen peroxide in milk samples were studied and Fe-BCAMW showed excellent selectivity. Sensitivity and reproducibility results showed that Fe-BC samples produced are promising material in the measurement of H2O2.