Electrochemical dissolution of metallic platinum in ionic liquids

The electrochemical dissolution of Pt in several ionic liquids (IL’s) was studied. Different IL’s were tested assessing their potential to dissolve Pt. Dissolution rate and current efficiency were evaluated. The main focus was on Cl containing IL’s: first generation, eutectic based IL’s and second generation IL’s with discrete anions. Pt dissolution only occurred in type 1 eutectic-based IL’s with a max. dissolution rate of 192.2 g m^?2 h^?1 and a max. current efficiency of 99 % for the ZnCl₂-1-ethyl-3-methylimidazolium chloride IL, and 9.090 g m^?2 h^?1 and 96 % for the 1:1 ZnCl₂–choline chloride ionic liquid. The dissolution occurred via the formation of [PtCl _x ] ^y? complexes. To form these complexes, addition of a metal chloride was necessary. Furthermore, an IL with an electrochemical window of 1.5 V, preferably 2.0 V is required to achieve Pt dissolution. The added metal salt needed to have a higher decomposition potential than 1.5 V or should be a Pt salt.     

Nitrous oxide and methane emissions from cultivated seasonal wetland (dambo) soils with inorganic,organic and integrated nutrient management

In many smallholder farming areas southern Africa, the cultivation of seasonal wetlands (dambos) represent an important adaptation to climate change. Frequent droughts and poor performance of rain-fed crops in upland fields have resulted in mounting pressure to cultivate dambos where both organic and inorganic amendments are used to sustain crop yields. Dambo cultivation potentially increases greenhouse gas (GHG) emissions. The objective of the study was to quantify the effects of applying different rates of inorganic nitrogen (N) fertilisers (60, 120, 240 kg N ha^?1) as NH₄NO₃, organic manures (5,000, 10,000 and 15,000 kg ha^?1) and a combination of both sources (integrated management) on GHG emissions in cultivated dambos planted to rape (Brassica napus). Nitrous oxide (N₂O) emissions in plots with organic manures ranged from 218 to 894 µg m^?2 h^?1, while for inorganic N and integrated nutrient management, emissions ranged from 555 to 5,186 µg m^?2 h^?1 and 356–2,702 µg m^?2 h^?1 respectively. Cropped and fertilised dambos were weak sources of methane (CH₄), with emissions ranging from ?0.02 to 0.9 mg m^?2 h^?1, while manures and integrated management increased carbon dioxide (CO₂) emissions. However, crop yields were better under integrated nutrient management. The use of inorganic fertilisers resulted in higher N₂O emission per kg yield obtained (6–14 g N₂O kg^?1 yield), compared to 0.7–4.5 g N₂O kg^?1 yield and 1.6–4.6 g N₂O kg^?1 yield for organic manures and integrated nutrient management respectively. This suggests that the use of organic and integrated nutrient management has the potential to increase yield and reduce yield scaled N₂O emissions.     

VOLATILE ORGANIC COMPOUND (VOC) REMOVAL BY ADSORPTION ONTO ACTIVATED CARBON FIBER CLOTH AND ELECTROTHERMAL DESORPTION: AN INDUSTRIAL APPLICATION

ABSTRACT

Previous studies have shown good adsorption of volatile organic compounds (VOC) present in air onto activated carbon fiber cloths (ACFCs). In a chemical plant, a treatment process was carried out to control a gaseous emission (flow close to 100 m³ h^?1) loaded with methylene chloride at concentrations ranging between 3 and 30 g m^?3. A final mass flow lower than 100 g h^?1 was required in the outlet emission. Two identical cylindrical ACFC modules worked alternately in an adsorption-desorption cycle. The outlet pollutant mass flow was found to be less than 4 g h^?1. After saturation of the adsorbent, the module was electrothermally regenerated. Desorbed methylene chloride was recovered in a cryogenic trap and reused in the chemical processes of the plant. This system worked continuously for more than 18 months (24 h per day) with no operating problems and giving good performance in terms of VOC outlet emission concentrations.     

Morpholinium-based ionic liquid mixtures as electrolytes in electrochemical double layer capacitors

Butyl-Methyl-Morpholinium bis(trifluoromethanesulphonyl)imide [ButMetMor][TFSI] and Ethyl-Methyl-Morpholinum bis(trifluoromethanesulphonyl)imide [EtMetMor][TFSI] and their mixtures with propylene carbonate (PC) were investigated as potential electrolytes in an electrochemical double layer capacitor (EDLC). Temperature dependencies of conductivity and electrochemical stability windows of ionic liquids (ILs) as well as their mixtures were determined. PC mixtures give higher conductivity with maximum ca. 1:4 (IL:PC) molar rate. Temperature dependencies of conductivity follow the Arrhenius type, showing higher energy activation for neat ILs rather than for mixtures. The EDLC was constructed based on activated carbon cloth (ACC, Kynol^®) ca. 2000 m² g^?1 and IL:PC mixture giving specific capacitance of ca. 100–120 F g^?1.     

Zinc(II) Extraction from Hydrochloric Acid Solutions using Amberlite XAD-7 Impregnated with Cyphos IL 101 (Tetradecyl(Trihexyl)Phosphonium Chloride)

Abstract

Cyphos IL 101 (tetradecyl(trihexyl)phosphonium chloride) was immobilized on Amberlite XAD-7. The extractant impregnated resin (EIR) was very efficient at removing Zn(II) from HCl solutions (optimum found between 2 and 4 M HCl). Metal ions were removed as anionic chlorocomplexes (ZnCl₄ ^2?) by ion exchange mechanism. The sorption strongly depended on the Cyphos IL 101 concentration in the EIR. The maximum sorption capacity was close to 20 mg Zn(II) g^?1 EIR (i.e. 0.40 mol Zn(II) mol^?1 Cyphos IL 101). The uptake kinetics were controlled by intraparticle diffusion (D_e: 1.2 10^?11 ? 6 10^?11 m² min^?1). Zn(II) can be easily desorbed using a number of eluents (including water and 0.1 M solution of HNO₃, H₂SO₄, and Na₂SO₄), which maintained performance levels over 5 cycles.     

Influence of metal salts in reaction medium on performance enhancement of novel aliphatic–aromatic-based polyamide thin-film composite osmosis membranes

In this study, we report an easy and novel way to develop high flux aliphatic–aromatic-based thin-film composite (TFC) polyamide osmosis membranes by addition of inorganic metal salts with amine reactants in the reaction system of polyethylene imine (PEI) and 1,3-benzene dicarbonyl chloride. Inorganic metal salts like CuSO₄, NiSO₄, MgSO₄, and Al₂(SO₄)₃ added to block some of the amine groups of PEI through complexation which in turn changes the polycondensation reaction kinetics of amine acid chloride reaction. The prepared membranes were characterized using water contact angle and atomic force microscopy studies and the performances were evaluated both in reverse osmosis and forward osmosis mode. In presence of metal salts in reaction interface, the performance of TFC membranes was greatly enhanced and the optimum metal salt concentration was identified for individual metal salts for maximum performance enhancement. The effects of different anions for same metal ion and different molecular weight of PEI were evaluated on composite polyamide membrane performances. Water permeability (flux) of 63.48 L m^?2 h^?1 was achieved upon inorganic salt addition compared to the unmodified TFC membranes with flux of 42.1 L m^?2 h^?1 at similar salt rejection of ~95%. Based on the new findings, a conceptual model was proposed to explain the role of metal ion in amine solution on the resulting characteristics of aromatic–aliphatic type polyamide–polysulfone composite membrane.     

Soil N<Subscript>2</Subscript>O fluxes in integrated production systems,continuous pasture and Cerrado

The objective of this study was to evaluate N₂O fluxes from integrated crop-livestock (ICL) and integrated crop-livestock forest (ICLF) systems, continuous pasture and native Cerrado. The experiment was conducted at Embrapa Cerrados, Planaltina-DF, in a Red Oxisol, between February 2012 and April 2014, following the transition of crop to livestock, which began in March 2012, with the sowing of Brachiaria brizantha cv. Piatã, intercropped with sorghum. The experimental design was a randomized block with three replications. The treatments were: cultivated area intercropped with rows of Eucalyptus, spaced 2 × 2 m between plants and 22 m between rows (ICLF); and an area cultivated without tree species (ICL), and also two adjacent reference areas: native Cerrado and continuous pasture. N₂O productions were characterized by fluxes below 20 μg N m^?2 h^?1. The ICL system had the highest cumulative flux with 2.84 kg N ha^?1, while the ICLF system obtained cumulative fluxes of 2.05 kg N ha^?1. The native Cerrado showed a negative balance, with –0.05 kg N ha^?1. The dry season was mostly characterized by low N₂O fluxes ranging between 10 μg N m^?2 h^?1 and negative values, whereas higher N₂O fluxes were observed after precipitation events, especially those following a long drought period. The water filled pore space was the factor that best explained N₂O fluxes, but higher fluxes were observed after the application of nitrogen fertilizer. There was a positive correlation between microbial biomass carbon and N₂O fluxes in the ICL and ICLF systems.     

SEPARATION OF MOLYBDENUM SPECIES BY ELECTRODIALYSIS

Lab-scale tests have been carried out in order to assess the possibility of separating molybdenum from aqueous solutions by means of electrodialysis (ED). Mo-containing sodium hydroxide, sulfuric acid, ammonium hydroxide, and hydrochloric acid solutions were tested at 25°C in a five-compartment ED cell. Cell voltages were markedly lower in ammonium hydroxide and chloride solutions, but separation in the latter electrolyte was limited by the low solubility of Mo species. Best results were achieved for Mo separation by ED from an aqueous alkaline solution with 21.8 g L^?1 Mo and 3.4 M ammonium hydroxide and a cell current density of 120 A m^?2. Under these conditions, the Mo transport rate from the working solution was 5.6 mol m^?2 h^?1 and the specific energy consumption for Mo separation was 2.2 kWh kg^?1. These results suggest that this operation should be further studied at pilot scale.     

3D Electrodes from aluminium foams prepared by replication process

Aluminium foams with pores displaying both regular size and distribution have been prepared by replication methods. Their volumetric density and electrical conductivity were 0.65 g cm^?3 and 2.44 MS m^?1, respectively. This method represents a simple way to produce 3D metal macroporous electrodes. In addition, the aluminium foam has been employed as support to produce 3D platinum electrodes (Pt/Al foam) by electrodeposition. The conditions for platinum electrodeposition have been established, and the electrodes were characterized by scanning electron microscopy and cyclic voltammetry. The electrocatalytic behaviour of the Pt/Al foam electrodes to methanol oxidation has been tested in 1 M CH₃OH + 0.5 M H₂SO₄ solutions.     

Enhanced gravimetric CO2 capacity and viscosity for ionic liquids with cyanopyrrolide anion

Ionic Liquids (ILs) are considered as alternative solvents for the separation of CO₂ from flue gas due mainly to their CO₂ affinity and thermal stability. The cation architecture in a matrix of ammonium and mostly phosphonium‐based ILs with 2‐cyanopyrrolide as the anion to evaluate its impact on gravimetric CO₂ absorption capacity, viscosity, and thermal stability and the three fundamental properties vital for application realization are systematically investigated. Among the investigated ILs, [P2,2,2,8][2‐CNpyr] demonstrated the lowest viscosity, 95 cP at 40°C, and highest CO₂ uptake, 114 mg CO₂ per g IL at 40°C. Combined effects of asymmetry and the optimized chain lengths also resulted in improved thermal stability for [P2,2,2,8][2‐CNpyr], with a mass loss rate of 1.35 × 10^?6 g h^?1 (0.0067 mass % h^?1) at 80°C. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2280–2285, 2015     

Preparation,characterization and application of iron (III)-loaded chitosan hollow fiber membranes as a new bio-based As (V) sorbent

Fe (III)-loaded chitosan (CS) hollow fibers (CS-Fe (III) HF) were successfully prepared according to the dry-wet spinning technique. The CS-Fe (III) HFs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA). Removal of pentavalent arsenic was studied through biosorption on CS-Fe (III) HF adsorptive membranes. The response surface methodology (RSM) was applied to investigate the influence of the main operating parameters such as contact time, pH, initial As (V) concentration and HFs dosage on the adsorption capacity of As (V). From the Pareto analysis, pH, [As (V)]_o, [CS-Fe (III) HF membranes] and squared effect of [As(V)]_o were found to produce the largest effect on biosorption of As (V). Kinetic studies showed that the pseudo-second-order kinetic model provides the best correlation to the experimental results. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 3,703 μg g^?1. A laboratory scale glass membrane module consisting of three CS-Fe(III) HFs has also been prepared and tested for biosorption of As (V) at a real scale. Permeability of As (V) ions through the CS-Fe (III) HF membranes was 0.145 μmol m^?2 h^?1 bar ^?1.     

Electrochemical oxidation of tannery wastewater

Tannery wastewater was treated by an electrochemical oxidation method using Ti/Pt, Ti/PbO₂ and Ti/MnO₂ anodes and a Ti cathode in a two‐electrode stirred batch reactor. The changes in colour concentration, chemical oxygen demand (COD), ammonia (NH₄⁺), sulfide and total chromium have been determined as a function of treatment time and applied current density. Gas chromatography–mass spectrometry (GC–MS) analysis, performed on the wastewater samples before and after treatment, as well as on foam samples, is reported. Anode efficiency, rate constants and energy consumption were estimated and discussed. The efficiency of Ti/Pt was 0.802 kgCOD h^?1 A^?1m^?2 and 0.270 kgNH₄⁺ h^?1 A^?1m^?2, and the energy consumption was 5.77 kWh kg^?1 COD and 16.63 kWh kg^?1 of NH₄⁺. The order of efficiency of anodes was found to be Ti/Pt ? Ti/PbO₂ > Ti/MnO₂. The results indicate that the electro‐oxidation method could be used for effective oxidation of tannery wastewater and a final effluent with substantially reduced pollution load can be obtained. © 2001 Society of Chemical Industry     

Nanoarchitectonics of Nanoporous Carbon Materials from Natural Resource for Supercapacitor Application

Nanoarchitectonics of nanoporous carbon materials (NCMs) derived from natural resource; Areca Catechu Nut (ACN) with enhanced electrochemical supercapacitance properties is reported. ACN powder is chemically activated in a tubular furnace at 400?°C and the effect of activating agent sodium hydroxide (NaOH), zinc chloride (ZnCl₂) and phosphoric acid (H₃PO₄) on the textural properties, surface functional groups and electrochemical supercapacitance properties was thoroughly examined. We found that ACN derived NCMs are amorphous in nature comprising of macropores, micropores and hierarchical micro- and mesopore architecture depending on the activating agent. Surface area and pore volume are found in the range 25–1985 m² g^?1 and 0.12–3.42 cm³ g^?1, respectively giving the best textural properties for H₃PO₄ activated NCM. Nevertheless, despite the different chemical activating agent used, all the prepared NCMs showed similar oxygen-containing surface functional groups (carboxyl, carboxylate, carbonyl and phenolic groups). The H₃PO₄ activated NCM showed excellent supercapacitance properties giving a high specific capacitance of ca. 342 F g^?1 at a scan rate of 5 mV s^?1 together with the high cyclic stability sustaining capacitance retention of about 97% after 5000 charging/discharging cycles. Electrochemical supercapacitance properties have demonstrated that the ACN derived novel nanoporous carbon material would be a potential material in energy storage application.     

Gold Recovery from HCl Solutions using Cyphos IL‐101 (a Quaternary Phosphonium Ionic Liquid) Immobilized in Biopolymer Capsules

Tetraalkyl phosphonium chloride (Cyphos IL‐101), an ionic liquid (IL), was tested for gold recovery from HCl solutions: first in liquid/liquid extraction systems (using toluene and hexane as solvent) and in a second step, after being immobilized in a biopolymer composite matrix. SEM‐EDAX analysis was used for the characterization of the resins. The sorption capacity reached up to 140 mg Au(III) g^?1 in 1 M HCl solutions. Base metals that do not form anionic chlorocomplexes and nitrate or chloride ions (at 5 g L^?1) did not interfere with Au(III) binding. Gold binding probably occurs through the interaction of R₃R'P⁺ with AuCl₄ ^?. The kinetics of sorption was carried out varying agitation speed, metal concentration, IL content, and resin drying. Intraparticle diffusion played an important role on the control of sorption kinetics. Gold could be desorbed from the loaded IL‐impregnated resin using thiourea (in HCl solutions). The resin could be re‐used for at least 4 cycles. The resins are specially adapted for the recovery of gold from low metal concentrations.     

Novel catalyst-support interaction for direct formic acid fuel cell anodes: Pd electrodeposition on surface-modified graphite felt

The electrodeposition of Pd on graphite felt (GF, thickness ~3 mm in uncompressed state) was studied and the resulting catalyst was compared with Pt-Ru/GF for the electro-oxidation of formic acid. A micellar solution composed of the non-ionic surfactant Triton X-102 and an aqueous phase containing PdCl₂ were utilized for the galvanostatic electrodeposition of Pd nanoparticles. The presence of the surfactant during electrodeposition coupled with pretreatment of the GF surface by a Shipley-type method (PdCl₂ + SnCl₂ solution) creating nucleation sites had a major impact on the Pd catalyst morphology and penetration throughout the electrode thickness, affecting, therefore, the electrocatalytic activity toward formic acid oxidation. It was found that large (~1,000 nm) Pd particles with smooth surface favored the indirect CO_ad pathway, while Pd nanoparticles (diameter <40 nm) with rough surface, formed with surfactant and pretreatment, were much more active leading to the direct non-CO_ad pathway. Due to pretreatment the GF surface has been modified and the effective catalytic system could be described as Pd/SnO₂–Pd(PdO)/GF with possible electronic interaction between support and catalyst. In direct formic acid fuel cell (DFAFC) experiments at 333 K and 1 M HCOOH, the peak power density using the Pd/GF anode reached 852 W m^?2 (57 g m^?2 Pd) compared to 392 W m^?2 (40 g m^?2 Pd) with a commercial Pd catalyst-coated membrane (CCM). The long-term stability of Pd-based anodes was poor and inferior to Pt–Ru (4:1 at. ratio) prepared and tested under identical conditions.     

Performance of wearable ionization air cleaners: Ozone emission and particle removal

Wearable ionization air cleaners are compact in size and marketed for personal respiratory protection by removing air pollutants from users' breathing zone. In this study, ozone emission and particle removal rates of four wearable ionization air cleaners (namely, AC1 through AC4) were evaluated inside a 0.46 m³ stainless steel chamber. Continuous measurements were conducted for ozone concentration, PM_2.5 concentration, and particle size distribution in the size range of 18.1–289 nm. Two of the four wearable air cleaners (i.e., AC1 and AC2) had detectable ozone emissions. The 10-h average ozone emission rates were quite different (i.e., 0.67 mg·h^?1 for AC1 and 3.40 × 10^?2 mg·h^?1 for AC2); however, the ozone emissions were negligible for AC3 and AC4. The number removal rates for particles within the measured size range were highly variable (i.e., 2.20 h^?1, 0.52 h^?1, 8.10 h^?1, and 27.9 h^?1 for AC1 through AC4, respectively). The corresponding mass removal rates of PM_2.5 were 1.85 h^?1, 0.48 h^?1_,1.52 h^?1, and 5.37 h^?1, respectively. Regulatory guidelines are needed to assure these devices can effectively remove particles without ozone emissions to protect public health.

Copyright © 2016 American Association for Aerosol Research     

Lewis acidity dependency of the electrochemical window of zinc chloride-1-ethyl-3-methylimidazolium chloride ionic liquids

Negative ion fast atom bombardment mass spectra (FAB-MS) recorded for ZnCl₂-1-ethyl-3-methylimidazolium chloride (ZnCl₂-EMIC) ionic liquids with various compositions indicate that various Lewis acidic chlorozincate clusters (ZnCl₃⁻, Zn₂Cl₅⁻ and Zn₃Cl₇⁻) are present in ZnCl₂-EMIC ionic liquids depending on the percentage of ZnCl₂ used in preparing the ionic liquids; higher ZnCl₂ percentage favors the larger clusters. Cyclic voltammetry reveals that the potential limits for a basic 1:3 ZnCl₂-EMIC melt correspond to the cathodic reduction of EMI⁺ and anodic oxidation of Cl⁻, giving an electrochemical window of approximately 3.0 V which is the same as that observed for basic AlCl₃-EMIC ionic liquids. For acidic ionic liquids that have a ZnCl₂/EMIC molar ratio higher than 0.5:1, the negative potential limit is due to the deposition of metallic zinc, and the positive potential limit is due to the oxidation of the chlorozincate complexes. All the acidic ionic liquids exhibit an electrochemical window of approximately 2 V, although the potential limits shifted in the positive direction with increasing ZnCl₂ mole ratio. Underpotential deposition of zinc was observed on Pt and Ni electrodes in the acidic ionic liquids. At proper temperatures and potentials, crystalline zinc electrodeposits were obtained from the acidic ionic liquids.     

Symbiotic nitrogen fixation by legumes in two Chinese grasslands estimated with the 15N dilution technique

Symbiotic nitrogen (N) fixation by legumes was investigated using the ¹⁵N dilution technique in two Chinese grasslands: one in the north-eastern Tibetan Plateau and the other in Inner Mongolia in China. A small amount (0.03 g N m^?2) of ¹⁵N labelled (NH₄)₂SO₄ fertilizer was evenly distributed in two soils. One month after the ¹⁵N addition, four legumes (Astragalus sp., Gueldenstaedtia diversifolia, Oxytropis ochrocephala and Trigonella ruthenica) in the alpine meadow and two legumes (Thermopsis lanceolata and Melissitus ruthenica) in the temperate steppe were collected. Several non-legume plant species were harvested as the reference. Above-ground biomass of legumes ranged from 8 to 24 g m^?2 in the alpine meadow and from 11 to 35 g m^?2 in the temperate steppe. The reference plants showed distinctly higher ¹⁵N atom% excess than legumes (0.08% vs. 0.02% in the alpine meadow, 0.10% vs. 0.02% in the temperate steppe). The N derived from atmosphere (%Ndfa) ranged from 50 to 90% N in the alpine meadow, while it ranged from 85 to 92% in the temperate steppe. Based on the legume above-ground biomass, total symbiotic N₂-fixation rate was estimated to be 1.00 g N m^?2 year^?1 in the alpine meadow and 1.15 g N m^?2 year^?1 in the temperate steppe. These N inputs by legumes can account for 9% of the gap between the N demand and the seasonal N release by mineralization in the alpine Kobresia grassland and 20% in the temperate Leymus grassland, respectively. Considering additional contribution of the root biomass, we suggest that biological N₂-fixation by legumes plays an important role in the cycling of N in both Kobresia and Leymus grasslands on an annual scale.     

Net ecosystem CO2 exchange and carbon cycling in tropical lowland flooded rice ecosystem

The seasonal fluxes of CO₂ and its characteristics with relation to environmental variables were investigated under tropical lowland flooded rice paddies employing the open path eddy covariance technique. The seasonal net ecosystem carbon budget was quantified by empirical modelling approach. The integrated net ecosystem exchange (NEE), gross primary production (GPP) and ecosystem respiration (RE) in the flooded rice field was ?448, 811 and 363 g C m^?2 in wet season. Diurnal variations of mean NEE values during the season varied from +3.99 to ?18.50 μmol CO₂ m^?2 s^?1. The daily average NEE over the cropping season varied from +2.73 to ?7.74 g C m^?2 day^?1. The net ecosystem CO₂ exchange reached its maximum in heading to flowering stage of rice with an average value of ?5.67 g C m^?2 day^?1. On daily basis the flooded rice field acted as a net sink for CO₂ during most of the times in growing season except few days at maturity when it became a net CO₂ source. The rate of CO₂ uptake by rice as observed from negative NEE values increased proportionally with air temperature up to 34 °C. The carbon distribution in different component of soil-plant system namely, soil organic carbon, dissolved organic carbon, methane emission, rhizodeposition, carbon in algal biomass, crop harvest and residues were quantified and carbon balance sheet was prepared for the wet season in tropical rice. Carbon balance sheet for tropical rice revealed 7.12 Mg C ha^?1 was cycled in the system in wet season.     

A microbial fuel cell using manganese oxide oxygen reduction catalysts

Microbial fuel cells (MFCs) are a potential method for enhanced water and waste treatment, which offer the additional benefit of energy generation. Manganese oxide was prepared by a simple chemical oxidation using potassium permanganate. Carbon-supported manganese oxide nanoparticles were successfully characterised as cathode materials for MFCs. The manganese oxide particles when used in a two-chamber MFC, using inoculum from an anaerobically digested sewage sludge, were found to exhibit similar oxygen reduction performance to that in separate electrochemical tests. MFC tests were conducted in a simple two chamber cell using aqueous air-saturated catholytes separated from the anode chamber by a Nafion membrane. MFC peak power densities were ca. 161 mW m^?2 for MnO _x /C compared to 193 mW m^?2 for a benchmark Pt/C, in neutral solution at room temperature. The catalyst materials demonstrated good stability in the 7.0–10.0 pH range. Theoretical (IR free) peak power densities were 937 mW m^?2 for MnO _x /C compared with 1037 mW m^?2 for Pt/C in the same experimental conditions: showing the MFCs performances can easily be improved by using more favourable conditions (more conductive electrolyte, improved cathode catalyst etc.). Our studies indicated that the use of our low cost MnO _x /C catalysts is of potential interest for the future application of MFC systems.