Synthesis, Characterization, and Humidity Detection Properties of Nb₂O₅ Nanorods and SnO₂/Nb₂O₅ Heterostructures

Nanostructured metal oxide semiconductors are ideally suited for their integration in different devices due to their high thermal and mechanical stability, unique electronic characteristics, and low-cost fabrication. The modification of their surface allows the design of heterostructures with novel properties. In this work, we have synthesized single-crystalline niobium pentoxide (Nb₂O₅) nanorods and niobium-pentoxide-coated tin oxide (Nb₂O₅/SnO₂) heterostructures by chemical vapor deposition. HR-TEM analysis and computer simulation studies showed the low density of defects and high crystallinity of the Nb₂O₅ nanorods, which exhibited high sensitivity toward humidity at low temperatures (60 °C). The fabrication of SnO₂/Nb₂O₅ core–shell heterostructures combines the high sensitivity of Nb₂O₅ shell toward moisture with the good electrical conductivity of SnO₂. The growth of the nanoscopic Nb₂O₅ overlayer on SnO₂ nanowires introduces defects in the structure, which influence the electronic properties of the material and enable the design of more efficient humidity sensors

High Electrocatalytic Response of a Mechanically Enhanced NbC Nanocomposite Electrode Toward Hydrogen Evolution Reaction

Resistant and efficient electrocatalysts for hydrogen evolution reaction (HER) are desired to replace scarce and commercially expensive platinum electrodes. Thin-film electrodes of metal carbides are a promising alternative due to their reduced price and similar catalytic properties. However, most of the studied structures neglect long-lasting chemical and structural stability, focusing only on electrochemical efficiency. Herein we report on a new approach to easily deposit and control the micro/nanostructure of thin-film electrodes based on niobium carbide (NbC) and their electrocatalytic response. We will show that, by improving the mechanical properties of the NbC electrodes, microstructure and mechanical resilience can be obtained while maintaining high electrocatalytic response. We also address the influence of other parameters such as conductivity and chemical composition on the overall performance of the thin-film electrodes. Finally, we show that nanocomposite NbC electrodes are promising candidates toward HER and, furthermore, that the methodology presented here is suitable to produce other transition-metal carbides with improved catalytic and mechanical properties