Catalysis of oxygen reduction in PEM fuel cell by seawater biofilm

The catalysis of oxygen reduction on metallic materials has been widely studied in the domain of aerobic corrosion. In this framework, it has been stated that seawater biofilms are able to catalyse efficiently oxygen reduction on stainless steels. This capacity was transferred here to the catalysis of the cathodic reaction of a proton exchange membrane fuel cell. A laboratory-scale fuel cell was designed with a stainless steel cathode, a platinum anode, and two separated liquid loops. The cathodic loop was air-saturated, while the anodic loop was hydrogen saturated. Seawater biofilm was previously grown on the stainless steel cathode, which was then set up into the fuel cell. The presence of the seawater biofilm on the stainless steel surface led to efficient catalysis of oxygen reduction. The biofilm-covered cathode was able to support current density up to 1.89 A/m2. Power density of 0.32 W/m2 was supplied with 1.34 A/m2 current density

Microbial catalysis of the oxygen reduction reaction for microbial fuel cells: a review.

The slow kinetics of the electrochemical oxygen reduction reaction (ORR) is a crucial bottleneck in the development of microbial fuel cells (MFCs). This article firstly gives an overview of the particular constraints imposed on ORR by MFC operating conditions: neutral pH, slow oxygen mass transfer, sensitivity to reactive oxygen species, fouling and biofouling. A review of the literature is then proposed to assess how microbial catalysis could afford suitable solutions. Actually, microbial catalysis of ORR occurs spontaneously on the surface of metallic materials and is an effective motor of microbial corrosion. In this framework, several mechanisms have been proposed, which are reviewed in the second part of the article. The last part describes the efforts made in the domain of MFCs to determine the microbial ecology of electroactive biofilms and define efficient protocols for the formation of microbial oxygen-reducing cathodes. Although no clear mechanism has been established yet, several promising solutions have been recently proposed

Hydrogen production by electrolysis of a phosphate solution on a stainless steel cathode

The catalytic properties of phosphate species, already shown on the reduction reaction in anaerobic corrosion of steels, are exploited here for hydrogen production. Phosphate species work as a homogeneous catalyst that enhances the cathodic current at mild pH values. A voltammetric study of the hydrogen evolution reaction is performed using phosphate solutions at different concentrations on 316L stainless steel and platinum rotating disk electrodes. Then, hydrogen is produced in an electrolytic cell using a phosphate solution as the catholyte. Results show that 316L stainless steel electrodes have a stable behaviour as cathodes in the electrolysis of phosphate solutions. Phosphate (1 M,pH 4.0/5.0) as the catholyte can equal the performance of a KOH 25%w solution with the advantage of working at mild pH values. The use of phosphate and other weak acids as catalysts of the hydrogen evolution reaction could be a promising technology in the development of electrolysis units that work at mild pH values with low-cost electrodes and construction materials

Marine microbial fuel cell : use of stainless steel electrodes as anode and cathode materials

Numerous biocorrosion studies have stated that biofilms formed in aerobic seawater induce an efficient catalysis of the oxygen reduction on stainless steels. This property was implemented here for the first time in a marine microbial fuel cell (MFC). A prototype was designed with a stainless steel anode embedded in marine sediments coupled to a stainless steel cathode in the overlying seawater. Recording current/potential curves during the progress of the experiment confirmed that the cathode progressively acquired effective catalytic properties. The maximal power density produced of 4mWm−2 was lower than those reported previously with marine MFC using graphite electrodes. Decoupling anode and cathode showed that the cathode suffered practical problems related to implementation in the sea, which may found easy technical solutions. A laboratory fuel cell based on the same principle demonstrated that the biofilm-covered stainless steel cathode was able to supply current density up to 140mAm−2 at +0.05V versus Ag/AgCl. The power density of 23mWm−2 was in this case limited by the anode. These first tests presented the biofilm-covered stainless steel cathodes as very promising candidates to be implemented in marine MFC. The suitability of stainless steel as anode has to be further investigated

Checking graphite and stainless anodes with an experimental model of marine microbial fuel cell

A procedure was proposed to mimic marine microbial fuel cell (MFC) in liquid phase. A graphite anode and a stainless steel cathode which have been proven, separately, to be efficient in MFC were investigated. A closed anodic compartment was inoculated with sediments, filled with deoxygenated seawater and fed with milk to recover the sediment’s sulphide concentration. A stainless steel cathode, immersed in aerated seawater, used the marine biofilm formed on its surface to catalyze oxygen reduction. The cell implemented with a 0.02 m2-graphite anode supplied around 0.10 W/m2 for 45 days. A power of 0.02 W/m2 was obtained after the anode replacement by a 0.06 m2-stainless steel electrode. The cell lost its capacity to make a motor turn after one day of operation, but recovered its full efficiency after a few days in open circuit. The evolution of the kinetic properties of stainless steel was identified as responsible for the power limitation

Piles à combustible utilisant des enzymes et des biofilms comme catalyseurs.

La biocatalyse des réactions anodiques ou cathodiques est à l’origine des mécanismes de biocorrosion et fait partie des phénomènes redoutés par les utilisateurs de matériaux métalliques. Cette biocatalyse peut être utilisée de manière positive pour augmenter les vitesses des réactions électrochimiques qui se produisent à l’anode et à la cathode de piles à combustible. À l’heure où les piles à combustible font l’objet de nombreuses recherches pour diminuer leur coût et améliorer leurs performances, la mise en oeuvre de bactéries dans des biofilms ou l’utilisation d’enzymes comme catalyseurs deviennent des solutions alternatives crédibles et galvanisent les recherches en France et à l’étranger

Micro-Mechanical Analysis of Corrosion Products Formed During Long-Term Carbonation Induced Corrosion of Steel

During corrosion distinct types of corrosion products form, composed of different ratios of ferrous ions and oxide, hydroxides. Corrosion products have different physical and mechanical properties, mainly density, resistivity, volume and modulus of elasticity compared to iron. Knowing properties of corrosion products is indispensable for service life modelling of structures and can give valuable insight into the long-term corrosion propagation process. In this study micro-indentation method was used to evaluate mechanical properties of different layers formed during long-term carbonation induced corrosion of steel in concrete. Investigation was performed on three sets of reinforced concrete samples, that underwent corrosion during 50, 60 and 70 years. Raman microspectroscopy was performed locally to determine and locate the constitutive phases of the corrosion system and to correlate them to the results of micro-indentation. Using grid technique, spatial distribution of phases with different mechanical properties was obtained for samples of different age. Comparison of values of mechanical properties for the same phases obtained on different samples, allowed hypothesis on their long-term behaviour

Marine floating microbial fuel cell involving aerobic biofilm on stainless steel cathodes

Here is presented a new design of a floating marine MFC in which the inter-electrode space is constant. This design allows the generation of stable current for applications in environments where the water column is large or subject to fluctuations such as tidal effects. The operation of the first prototype was validated by running a continuous test campaign for 6 months. Performance in terms of electricity generation was already equivalent to what is conventionally reported in the literature with basic benthic MFCs despite the identification of a large internal resistance in the proposed design of the floating system. This high internal resistance is mainly explained by poor positioning of the membrane separating the anode compartment from the open seawater. The future objectives are to achieve more consistent performance and a second-generation prototype is now being developed, mainly incorporating a modification of the separator position and a stainless steel biocathode with a large bioavailable surface

Contribution of cellular automata to the understanding of corrosion phenomena

We present a stochastic CA modelling approach of corrosion based on spatially separated electrochemical half-reactions, diffusion, acido-basic neutralization in solution and passive properties of the oxide layers. Starting from different initial conditions, a single framework allows one to describe generalised corrosion, localised corrosion, reactive and passive surfaces, including occluded corrosion phenomena as well. Spontaneous spatial separation of anodic and cathodic zones is associated with bare metal and passivated metal on the surface. This separation is also related to local acidification of the solution. This spontaneous change is associated with a much faster corrosion rate. Material morphology is closely related to corrosion kinetics, which can be used for technological applications.Comment: 13 pages, 9 figure

Dispositif d’électrolyse de l’eau et son utilisation pour produire de l’hydrogène

Dispositif d’électrolyse destiné à produire de l’hydrogène par réduction de l’eau comprenant un compartiment cathodique, un compartiment anodique, un élément reliant lesdits compartiments et permettant la migration des ions entre eux, le dispositif étant caractérisé en ce que le compartiment cathodique contient au moins un acide faible apte à catalyser la réduction et une solution électrolytique dont le pH est dans la gamme comprise entre 3 et 9