Air-breathing bio-cathodes based on electro-active biochar from pyrolysis of Giant Cane stalks. (15th February 2019)

• Record Type: Journal Article
• Authors: Marzorati, S.; Goglio, A.; Fest-Santini, S.; Mombelli, D.; Villa, F.; Cristiani, P.; Schievano, A.
• Is Part Of: International journal of hydrogen energy. Volume 44:Number 9(2019)
• Page Start: 4496
• Page End: 4507
• Publication Date: 2019-02-15
• Subjects: Electroactive biochar -- e-biochar -- Bio-electrochemical systems -- Air-cathode -- Wastewater treatment -- Pyrolysis; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2018.07.167
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: An innovative low-tech solution to fabricate electro-active biochar ( e- biochar) electrodes for bio-electrochemical systems (BES) is proposed. Ligno-cellulosic stalks of Giant Cane ( Arundo Donax L.) were subjected to pyrolysis treatment at 900 °C for 1 h. The material kept its original hollow cylindrical shape, rigid morphology and porous texture, as confirmed by 3DX-ray micro-computed tomography. These characteristics are suitable for its use at the air-water interface in BES, as air-breathing bio-cathodes. BET (Brunauer-Emmett-Teller) specific surface area was equal to 114 ± 4 m 2 g −1, with more than 95% of pores in the microporosity range (pore diameter < 1 nm). Surface electrocatalytic activity was sufficient to sustain oxygen reduction reaction at pH 7, in terms of both onset potential (−0.02 V vs Ag/AgCl) and reduction limiting current density (1 A m −2 ). Electrical resistivity measurements confirmed sufficient conductivity (8.9 × 10 −3 ± 1 × 10 −4 Ω m) of the material and Raman spectroscopy allowed to estimate a graphitization degree in relation to the ID /IG, equal to 2.26. In parallel, the e -biochar were tested as air-exposed bio-cathodes in BES, coupled to carbon cloth bio-anodes. After inoculation with wastewater from swine-farming, current densities were generated in the range of 100–150 mA m −2, along more than 2 months of operation, under sodium acetate feeding. Confocal laser scanning imaging revealed consistent biofilm formation on the water-side surface of the cathodes, while a nearly-complete absence of it at the air-side. These e- biochar electrodes might open innovative perspectives to scale-up BES for different applications. Here, consistent salts depositions on the material after 70 days of exposure to the wastewater, suggest that e- biochar biocathodes might serve to recycle nutrients to agricultural soils, through minerals-enriched biochar. Highlights: Rigid carbonaceous cylinders were obtained by 900 °C pyrolysis of Giant Canes. Pyrolysed Giant Canes possess a microporous texture and are conductive. Pyrolysed cylinders were used as electro-active biochar-based cathodes ( e- biochar). The need of technological materials in bio-electrochemical systems is reduced. Salts deposition clogged the porous texture and enriched e- biochar of minerals.