Composite‐modified anode by MnO2/polypyrrole in marine benthic microbial fuel cells and its electrochemical performance

Low power limits the application of microbial fuel cells (MFCs). Our research mainly focuses on the modification of the electrode and looking for new anode material for high‐power marine benthic microbial fuel cells(BMFCs). A MnO₂/PPy composite‐modified anode was fabricated by in situ chemical polymerization. Surface topography and properties were characterized by scanning electron microscopy and infrared spectroscopy, respectively, indicating that the MnO₂/PPy composite is of a ‘mosaic‐like’ microstructure. The electrochemical performance and wettability of different kinds of anode were investigated respectively. Cyclic voltammetry and linear sweep voltammetry tests show that MnO₂/PPy composite‐modified electrode has a typical capacitance feature; its capacitance is 3.1 times higher than that of unmodified electrode. Contact angle of the composite‐modified anode reduces to 46 ± 0.5°, and its kinetic activity increased for more than 1.1 times. The maximum output power density of MnO₂/PPy composite‐modified cell reached 562.7 ± 10 mW m^?2, which is 2.1‐fold of the unmodified one. Finally, the composite‐modified anode provides an alternative potential choice for high‐performance cell, and the possible influence mechanism of composite materials on the BMFCs was also analyzed. Copyright © 2016 John Wiley & Sons, Ltd.     

Oxygen‐modified multiwalled carbon nanotubes: physicochemical properties and capacitor functionality

Multiwalled carbon nanotubes (MWCNTs) have found numerous applications in energy conversion systems. The current work focused on the introduction of oxygen moieties onto the walls of MWCNTs by five different reagents and investigating the associated physicochemical properties. Oxygen‐containing groups were introduced onto MWCNTs using an ultrasound water‐bath treatment with HNO₃, HCl, H₂O₂ or HCl/HNO₃ solution. Physicochemical properties were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman, thermal gravimetric analysis, textural characteristics, cyclic voltammetry and electrochemical impedance spectroscopy. The study focus was mainly on linking the physicochemical properties of oxygen‐functionalised MWCNTs and suitability in electrochemical capacitors using group one sulfates. From the Fourier transform infrared spectroscopy KBr pellet protocol, peaks at 3400, 2370 and 1170 cm^?1 suggest oxygen‐containing functionalities on MWCNTs. HNO₃ treatment introduced highest oxygen‐containing moieties and achieved highest specific capacitance in Li₂SO₄ and Na₂SO₄ electrolytes of 36.200 F g^?1 (77 times better than pristine) and 45.100 F g^?1 (2.5 times enhancement), respectively. For K₂SO₄, it was 33.600 F g^?1 (4.9 times better) with HNO₃/HCl‐treated samples. Oxygen‐functionalised MWCNTs displayed both pseudo and electrochemical double‐layer mechanism of enhanced charge storage and cycle stability in group one sulfates electrolytes. The dominating charge storage mechanism was pseudo, and Na₂SO₄ was the best electrolyte amongst the three group one sulfates investigated. Copyright © 2017 John Wiley & Sons, Ltd.     

Comparative study on the electrochemical performance of coals and coal chars in a molten carbonate direct carbon fuel cell with a novel anode structure

Molten carbonate direct carbon fuel cells (MC-DCFCs) allow the efficient and clean use of coal. In this study, a novel anode structure is designed, and the performances of six coal-based fuels are investigated in MC-DCFC. The mechanisms of performance differences are investigated, as well as the effect of operating temperature on performance. The results reveal the fuel cell performance in the following order: meagre coal (109.8) ≈ bituminous coal (108.7) > bituminous coal char (98.1) > lignite coal (83.7) > lignite coal char (71.3) > meagre coal char (53.2) in mW cm^?2. Coal performs better because of its high carbon content, high volatile content, rich oxygen-containing functional groups, larger specific surface area, stronger thermal reactivity, and other factors. The electrochemical reactivity of coal fuel increased with higher reaction temperatures and varied throughout the temperature ranges. This study implies that using coal fuel to commercialize MC-DCFC could be a realistic alternative.