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Catalytic oxidation of methane to methanol over oxo-doped ZIF-204 can occur with negligible transition energy barriers. High charge of the doped oxo is effective for methane capturing via hydrogen bonds and for C–H σ-bond weakening.

Transparent-flexible thermoelectric materials are attractive for future small-sized consumer electronics, the internet of things, and wearable devices. The microstructural evolution and subsequent thermoelectric properties of Ti 1%.at-doped ZnO thin films, grown on polyimide flexible substrates, are presented. The thin films were grown using radio frequency a magnetron sputtering method followed by annealing for 60 min at temperatures of 200–400 °C under vacuum atmosphere. Post-annealed films demonstrate a hexagonal Wurtize structure. It is found that the annealing helped to relax residual stresses in the thin films, subsequently leading to enhanced charge concentration, carrier mobility, mean free path, and density-of-states effective mass. The thin film, annealed at 300 °C, illustrates the highest power factor of the films measured at room temperature at 19.10 μW m−1 K−2. Further increases in the annealing temperature suggest Ti2+ diffuses into the ZnO lattice and in turn disturbs the crystalline structure; this results in a reduction of the power factor to 9.32 μW m−1 K−2 at an annealing temperature of 350 °C.

In this paper, thermoelectric performance of the ZnO thin films were investigated via doping (Gallium - Ga and Indium - In) and post-thermal treatment. Various kinds of defects, such as zinc (Zn) vacancies, Ga substitute for Zn, zinc interstitials, oxygen vacancies, oxygen interstitials, oxygen antisite, were induced in the ZnO thin films by doping with Ga, In and post-thermal treatment. Annealed thin films have better thermoelectric performance than unannealed thin films. The figure of merit ZT values at 300 °C were 0.114 and 0.186 for the single Ga-doped ZnO (GZO@500) and dually In, Ga doped ZnO (IGZO@500) thin films annealed at 500 °C, respectively. Higher concentration of zinc interstitial led the GZO@500 thin film to have larger power factor and larger total thermal conductivity, resulting in lower ZT than the IGZO@500 thin film. To the best of our knowledge, the ZT value of 0.186 at 300 °C obtained from our IGZO@500 thin films is the highest ever reported for n-type ZnO based thin films.

ZnO/CuO nanocomposites were derived from a metal-organic framework (MOF) using a simple precipitation method. The mesoporous nature, crystallinity, and fine particle size of the synthesized ZnO/CuO nanocomposites varied with CuO amounts, affecting the gas sensing ability of different gases (H2S, CO, C6H6, and C7H8 gases). It was found that the ZnO/CuO (40 mol%) gas sensor showed the highest sensing capacity in terms of response, selectivity, and repeatability on low concentrations of H2S gas (10 ppm). The strong sensing performance, short response time (58 s) and recovery time (273 s) were explained in terms of the texture coefficients (phase percentage, crystal size, and crystallinity) of the ZnO and CuO phase compositions, resulting in the formation of a high number of p-n junctions and quantum confinement effects in the nanocomposite, as well as the lower binding energy of H2S. The fast sensing ability of a low H2S concentration highlights the practical importance of these MOF-derived ZnO/CuO nanocomposites.

Mg-doped CuCrO2 material has emerged as a p-type semiconductor, especially, in the field of thermoelectric materials because of its lowest resistivity in delafossite material family. In this work, CuCr0.95Mg0.05O2 bulk materials were prepared in a series of sintering temperatures including 1000, 1200, and 1400°C using solid-state reaction method. From XRD results, all samples exhibit the significant existence of delafossite phase CuCrO2, and a small portion belongs to the spinel phase MgCr2O4. An interesting finding in this study is that the Vickers hardness is mainly governed by the crystallite size of (110) plane. Besides, the change in the crystallite size of (110) plane also indirectly affects the carrier concentration of the compounds with increasing sintering temperature. The highest power factor (PF) was reached for the sample prepared at the sintering temperature 1400°C with the value of 193 μW/mK2 along with the Seebeck coefficient value of 600 μV/K measured at 400°C.

Introduction: Harvesting the waste heat emitted from the activities of humanity based on thermoelectric devices is an appropriate way to reduce the overconsumption of fossil fuel nowadays. Methods: In this work, CuCr0:85Mg0:15O2 compounds prepared by conventional solid-state reaction method were investigated to find out that the short sintering time is enough for thermoelectric applications, directly low the cost of the devices. Results and Conclusion: We find out that there is a significant change in the crystal structure, the chemical state, and thermoelectric properties along with the increase of the sintering time, but eventually, the dimensionless figure of merit ZT is almost constant regardless of the long or short sintering time which means that the increase of electrical conductivity will compromise the increase of thermal conductivity. The highest ZT value is 0.03 measured at 500 oC for both samples prepared at the sintering time of 3 and 12 hours.