Undesired bulk oxidation of LiMn2O4 increases overpotential of electrocatalytic water oxidation in lithium hydroxide electrolytes

Chemical and structural changes preceding electrocatalysis obfuscate the nature of the active state of electrocatalysts for the oxygen evolution reaction OER , which calls for model systems to gain systematic insight. We investigated the effect of bulk oxidation on the overpotential of ink casted LiMn2O4 electrodes by a rotating ring disk electrode RRDE setup and X ray absorption spectroscopy XAS at the K shell core level of manganese ions Mn K edge . The cyclic voltammogram of the RRDE disk shows pronounced redox peaks in lithium hydroxide electrolytes with pH between 12 and 13.5, which we assign to bulk manganese redox based on XAS. The onset of the OER is pHdependent on the scale of the reversible hydrogen electrode RHE with a Nernst slope of 40 4 mV pH at 5 amp; 956;A monitored at the RRDE ring. To connect this trend to catalyst changes, we develop a simple model for delithiation of LiMn2O4 in LiOH electrolytes, which gives the same Nernst slope of delithiation as our experimental data, i.e., 116 25 mV pH. From this data, we construct an ERHE pH diagram that illustrates robustness of LiMn2O4 against oxidation above pH 13.5 as also verified by XAS. We conclude that manganese oxidation is the origin of the increase of the OER overpotential at pH lower than 14 and also of the pH dependence on the RHE scale. Our work highlights that vulnerability to transition metal redox may lead to increased overpotentials, which is important for the design of stable electrocatalyst

Microsatellite diversity of the Nordic type of goats in relation to breed conservation: how relevant is pure ancestry?

In the last decades, several endangered breeds of livestock species have been re-established effectively. However, the successful revival of the Dutch and Danish Landrace goats involved crossing with exotic breeds and the ancestry of the current populations is therefore not clear. We have generated genotypes for 27 FAO-recommended microsatellites of these landraces and three phenotypically similar Nordic-type landraces and compared these breeds with central European, Mediterranean and south-west Asian goats. We found decreasing levels of genetic diversity with increasing distance from the south-west Asian domestication site with a south-east-to-north-west cline that is clearly steeper than the Mediterranean east-to-west cline. In terms of genetic diversity, the Dutch Landrace comes next to the isolated Icelandic breed, which has an extremely low diversity. The Norwegian coastal goat and the Finnish and Icelandic landraces are clearly related. It appears that by a combination of mixed origin and a population bottleneck, the Dutch and Danish Land-races are separated from the other breeds. However, the current Dutch and Danish populations with the multicoloured and long-horned appearance effectively substitute for the original breed, illustrating that for conservation of cultural heritage, the phenotype of a breed is more relevant than pure ancestry and the genetic diversity of the original breed. More in general, we propose that for conservation, the retention of genetic diversity of an original breed and of the visual phenotype by which the breed is recognized and defined needs to be considered separately