Bimetallic, nanostructured materials hold promise for improving catalyst activity and selectivity, yet little is known about the dynamic compositional and structural changes that these systems undergo during pretreatment that leads to efficient catalyst function. Here we use ozone-activated silver-gold alloys in the form of nanoporous gold as a case study to demonstrate the dynamic behaviour of bimetallic systems during activation to produce a functioning catalyst. We show that it is these dynamic changes that give rise to the observed catalytic activity. Advanced in situ electron microscopy and X-ray photoelectron spectroscopy are used to demonstrate that major restructuring and compositional changes occur along the path to catalytic function for selective alcohol oxidation. Transient kinetic measurements correlate the restructuring to three types of oxygen on the surface. The direct influence of changes in surface silver concentration and restructuring at the nanoscale on oxidation activity is demonstrated. Our results demonstrate that characterization of these dynamic changes is necessary to unlock the full potential of bimetallic catalytic materials.

The protonic ceramic electrochemical cell (PCEC) is an emerging and attractive technology that converts energy between power and hydrogen using solid oxide proton conductors at intermediate temperatures. To achieve efficient electrochemical hydrogen and power production with stable operation, highly robust and durable electrodes are urgently desired to facilitate water oxidation and oxygen reduction reactions, which are the critical steps for both electrolysis and fuel cell operation, especially at reduced temperatures. In this study, a triple conducting oxide of PrNi 0.5 Co 0.5 O 3-δ perovskite is developed as an oxygen electrode, presenting superior electrochemical performance at 400~600°C. More importantly, the selfsustainable and reversible operation is successfully demonstrated by converting the generated hydrogen in electrolysis mode to electricity without any hydrogen addition. The excellent electrocatalytic activity is attributed to the considerable proton conduction, as confirmed by hydrogen permeation experiment, remarkable hydration behavior and computations.

Sleep control is ascribed to a two-process model, a widely accepted concept that posits homoeostatic drive and a circadian process as the major sleep-regulating factors. Cognitive and emotional factors also influence sleep–wake behaviour; however, the precise circuit mechanisms underlying their effects on sleep control are unknown. Previous studies suggest that adenosine has a role affecting behavioural arousal in the nucleus accumbens (NAc), a brain area critical for reinforcement and reward. Here, we show that chemogenetic or optogenetic activation of excitatory adenosine A2A receptor-expressing indirect pathway neurons in the core region of the NAc strongly induces slow-wave sleep. Chemogenetic inhibition of the NAc indirect pathway neurons prevents the sleep induction, but does not affect the homoeostatic sleep rebound. In addition, motivational stimuli inhibit the activity of ventral pallidum-projecting NAc indirect pathway neurons and suppress sleep. Our findings reveal a prominent contribution of this indirect pathway to sleep control associated with motivation.

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A series of zirconia-supported copper oxide catalysts synthesized by decomposition of the oxalate precursors formed by oxalate gel-coprecipitation in alcoholic solution were extensively investigated in relation to their performance in methanol steam reforming. The combination of different techniques (N 2 adsorption, X-ray diffraction (XRD), N 2 O titration, H 2 -TPR, diffuse reflectance Fourier transform infrared, Raman, and X-ray photoelectron spectroscopy) in the characterization of Cu/ZrO 2 catalysts shows that the surface and structural characteristics of the zirconia phase as well as the dispersion and nature of the copper species depend strongly on the calcination temperature. Temperature-programmed reduction patterns reveal the presence of three types of copper species on the ZrO 2 support. XRD results indicate that, depending on the calcination temperature, a substantial incorporation of Cu species into the zirconia lattice leading to a strong Cu-ZrO 2 metal-support interaction may occur. The N 2 O titration reveals that the 550 °C calcined material exhibits the highest metallic copper surface area as compared to other samples, as opposed to in situ XRD analysis showing that the lower the calcination temperature the higher the copper dispersion. Spectroscopic measurements reveal that the phase transformation of zirconia from tetragonal to monoclinic takes place initially at the surface regions of the Cu-ZrO 2 sample, as evidenced from the fact that the monoclinic phase can be detected first by Raman spectroscopies for the samples calcined at a lower temperature than by XRD. The highest activity was achieved for the 550 °C calcined material, illustrating that the creation of monoclinic phase enriched on the surface of tetragonal zirconia in Cu/ZrO 2 are beneficial for the generation of copper catalyst with enhanced activities.