Lithium-O2 (Li-O2) batteries are currently limited by a large charge overpotential at practically relevant current densities, and the origin of this overpotential has been heavily debated in the literature. This paper presents a series of electrochemical impedance measurements suggesting that the increase in charge potential is not caused by an increase in the internal resistance. It is proposed that the potential shift is instead dictated by a mixed potential of parasitic reactions and Li2O2 oxidation. The measurements also confirm that the rapid potential loss near the end of discharge ("sudden death") is explained by an increase in the charge transport resistance. The findings confirm that our theory and conclusions in ref 1, based on experiments on smooth small-area glassy carbon cathodes, are equally valid in real Li-O2 batteries with porous cathodes. The parameter variations performed in this paper are used to develop the understanding of the electrochemical impedance, which will be important for further improvement of the Li-air battery.

Increased use of natural gas as a fuel in efficient, lean-burning engines could offer environmental advantages, but this necessitates a catalytic oxidation of methane escaping from the engine. The challenge for the catalytic oxidation of CH4 is that the catalyst must operate in the exhaust, which contains H2O (5–15 vol %) and SO2 (∼1 ppm), and both components cause a severe inhibition of the catalyst. Here, we report that a 2 wt % Rh/ZSM-5 catalyst offers great promise by showing that high methane conversion can be reached at practically achievable conditions and high space velocities also in the presence of H2O and SO2. Rh-based catalysts, which are in the form of Rh2O3 under reaction conditions, become superior to the state-of-the-art Pd-based catalysts in an atmosphere with both H2O and SO2. Although both H2O and SO2 inhibit Pd and Rh catalysts, water is found to have a destabilizing effect on rhodium sulfate that enables a partial decomposition of the sulfate below 400 °C. We propose that this partly alleviates the sulfur poisoning of Rh catalysts; wherefore, the combined inhibition from H2O + SO2 is weaker for Rh than that for Pd.

A joint large-scale biogas plant treats animal manure together with organic industrial and household solid waste and produces biogas and organic fertilizers. In the presentation we will discuss the importance of combined treatment of manure and organic waste. Furthermore, data will be shown on the effects of addition of lipid- and protein- containing wastes to thermophilic digesters treating cattle manure.

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