Synthesis, characterization and application of tangerine peel-derived Fe3C/Fe-encapsulated biochar for electrochemical removal of environmental pollutant

Abstract

Conforming to the principles of green chemistry and sustainable environmental progress, this work demonstrated the concept of “treating waste with waste”, i.e. treating atmospheric pollutant sulfur dioxide (SO2) with agricultural waste of tangerine peel. SO2 electro-catalytic oxidation is the key technique in this endeavor, which utilizes SO2 as reaction raw material in the anode to remove it. The anodic SO2 electro-catalytic oxidation could be coupled to the cathodic hydrogen evolution to achieve the simultaneous SO2 removal and hydrogen production. Anodic catalyst plays a vital role in this SO2 transformation. In this work, tangerine peel has been re-utilized to afford tangerine peel-derived biochar (TPB) to prepare TPB/CNT-derived Fe3C/Fe/C (N-doped) as a capable anodic catalyst to achieve this goal. With help of various characterization techniques and electrochemical testing, the optimal iron mass fraction and pyrolysis temperature were found to be 16 wt% Fe under 800 °C, with carboxylated carbon nanotube as carbon additive. Transmission electron microscopy (TEM) image showed that the as-prepared TPB/CNT-derived Fe3C/Fe/C (N-doped) featured a unique morphology to encapsulate Fe3C/Fe with a layer of protecting carbon, which should contribute to the enhanced electro-catalytic performances. A flow electrolyzer was also assembled to illustrate practical application of the anodic catalyst in the real scenario. Owing to its lower cost, the as-prepared TPB/CNT-derived Fe3C/Fe/C (N-doped) will be advantageous to replace precious metals to mediate SO2 electro-catalytic oxidation as one of promising environmental treatment techniques in the future.