The production of hydrogen and the utilization of biomass for sustainable concepts of energy conversion and storage require gas sensors that discriminate between hydrogen (H 2 ) and carbon monoxide (CO). Mesoporous copper−ceria (Cu−CeO 2 ) materials with large specific surface areas and uniform porosity are prepared by nanocasting, and their textural properties are characterized by N 2 physisorption, powder XRD, scanning electron microscopy, transmission electron microscopy, and energydispersive X-ray spectroscopy. The oxidation states of copper (Cu + , Cu 2+ ) and cerium (Ce 3+ , Ce 4+ ) are investigated by XPS. The materials are used as resistive gas sensors for H 2 and CO. The sensors show a stronger response to CO than to H 2 and low cross-sensitivity to humidity. Copper turns out to be a necessary component; copper-free ceria materials prepared by the same method show only poor sensing performance. By measuring both gases (CO and H 2 ) simultaneously, it is shown that this behavior can be utilized for selective sensing of CO in the presence of H 2 .

Hydrothermal carbonization of trehalose, in contrast to other saccharides, leads to the formation of microspheres with a bimodal size distribution. The microspheres develop hierarchical porosity with micro-, meso-, and macro-pores after pyrolysis.