MFC cathode using PVDF binder and an activated carbon catalyst
-------- Forwarded Message -------- Subject: Re: MFC's Date: Wed, 24 Nov 2021 17:49:38 -0300 From: Cristiano Krug cristiano.krug@ufrgs.br To: Enfitec Júnior enfitecjunior@gmail.com
Oi.
A meu ver estão concorrendo para o cátodo as 3 opções abaixo. Eu penso que as opções 1 e 3 deveriam ser abandonadas e todo esforço deveria ser direcionado para a opção 2. Penso que essa abordagem deveria ser sugerida para a Regenera.
Cristiano
Opção 1 (a que vocês estão orçando): tela de aço (com platina)
Microbial Fuel Cell Cathodes With Poly(dimethylsiloxane) Diffusion Layers Constructed around Stainless Steel Mesh Current Collectors https://doi.org/10.1021/es903009d
The SS mesh (type 304 SS, 90 × 90, woven wire diameter 0.0055 in., McMaster-Carr, OH) had 90 × 90 openings per square inch. PDMS was made using a 10:1 mixture of SYLGARD 184 silicone elastomer base and SYLGARD 184 silicone elastomer curing agent (Dow Corning, MI), that was further diluted to 10 wt % with toluene to decrease the solution viscosity. The PDMS (6.25 mg/cm2) was applied with carbon black (1.56 mg/cm2) to the side of the SS that faced the air. After applying this first PDMS/carbon black as a base layer, additional DLs (one to four layers) containing PDMS/carbon black or only PDMS were applied on top of this base layer at the same mass loading as the original layer. After applying each layer, cathodes were air-dried for 2 h, and then heated at 80 °C for 30 min to cross-link the PDMS oligomers. After applying these DLs, a Pt catalyst layer (5 mg/cm2 10% Pt on Vulcan XC-72 with 33.3 μL/cm2 of 5 wt % Nafion as binder) was applied to the SS mesh on the side facing the solution (see ref 22 for detailed procedures).
Opção 2 (a descoberta de ontem): tela de aço, procedimento simples e sem platina!!!
Method published in Environmental Science & Letters, 1, 10, 416-420 https://pubs.acs.org/doi/abs/10.1021/ez5002769 https://youtu.be/ltpNaUFuzwA https://youtu.be/Z8EEg6akDHw
A simple one-step, phase inversion process was used here to construct an inexpensive MFC cathode using a poly(vinylidene fluoride) (PVDF) binder and an activated carbon catalyst. The phase inversion process enabled cathode preparation at room temperatures, without the need for additional heat treatment, and it produced for the first time a cathode that did not require a separate diffusion layer to prevent water leakage. MFCs using this new type of cathode produced a maximum power density of 1470 ± 50 mW m–2 with acetate as a substrate, and 230 ± 10 mW m–2 with domestic wastewater. These power densities were similar to those obtained using cathodes made using more expensive materials or more complex procedures, such as cathodes with a polytetrafluoroethylene (PTFE) binder and a poly(dimethylsiloxane) (PDMS) diffusion layer, or a Pt catalyst.
PVDF solutions with different concentrations of 5%, 7.5%, and 10% (w/v) were prepared by dissolving PVDF powder (∼534 000 Da; Sigma-Aldrich) in N,N-dimethylacetamide (DMAc), with vigorous stirring using a stir bar at room temperature (23 ± 1 °C) for over 8 h to completely dissolve the polymer. AC powder (Norit SX plus, Norit Americas Inc., TX) was applied at an optimum AC loading of 26.5 mg cm–2, based on previous experiments. Catalyst mixtures were prepared with different PVDF loadings (all mass ratios) of (1) 8.8 mg cm–2, AC/CB (Vulcan XC-72, Cabot Corporation, USA)/PVDF (10% as prepared) = 30:3:10; (2) 6.6 mg cm–2, AC/CB/PVDF (7.5%) = 30:3:7.5; (3) 4.4 mg cm–2, AC/CB/PVDF (7.5%) = 30:3:5. The mixtures were spread directly onto an 11.3 cm2 circular section of stainless steel mesh (50 × 50, type 304, McMaster-Carr, USA) with a spatula (except as noted). The cathodes were then immersed into deionized (DI) water for 15 min at room temperature to induce phase inversion. Cathodes were then air-dried in a fume hood for >6 h and stored in DI water prior to tests.
Opção 3: a novidade anterior, pyrolyzed iron(II) phthalocyanine (pyr-FePc) and cobalt tetramethoxyphenylporphyrin (pyr-CoTMPP)) ao invés de platina, mas ainda usando carbon cloth ao invés de tela de aço
Challenges and Constraints of Using Oxygen Cathodes in Microbial Fuel Cells https://doi.org/10.1021/es060332p
Microbial fuel cell performance with non-Pt cathode catalysts https://doi.org/10.1016/j.jpowsour.2007.07.010
(Esses compostos pyr-FePc e CoTMPP é que eu propus procurarmos no Instituto de Química.)