Direct CO2 capture and conversion to fuels on magnesium nanoparticles under ambient conditions simply using water

Converting CO₂ directly from the air to fuel under ambient conditions is a huge challenge. Thus, there is an urgent need for CO₂ conversion protocols working at room temperature and atmospheric pressure, preferentially without any external energy input. Herein, we employ magnesium (nanoparticles and bulk), an inexpensive and the eighth-most abundant element, to convert CO₂ to methane, methanol and formic acid, using water as the sole hydrogen source. The conversion of CO₂ (pure, as well as directly from the air) took place within a few minutes at 300 K and 1 bar, and no external (thermal, photo, or electric) energy was required. Hydrogen was, however, the predominant product as the reaction of water with magnesium was favored over the reaction of CO₂ and water with magnesium. A unique cooperative action of Mg, basic magnesium carbonate, CO₂, and water enabled this CO₂ transformation. If any of the four components was missing, no CO₂ conversion took place. The reaction intermediates and the reaction pathway were identified by ¹³CO₂ isotopic labeling, powder X-ray diffraction (PXRD), nuclear magnetic resonance (NMR) and in situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and rationalized by density-functional theory (DFT) calculations. During CO₂ conversion, Mg was converted to magnesium hydroxide and carbonate, which may be regenerated. Our low-temperature experiments also indicate the future prospect of using this CO₂-to-fuel conversion process on the surface of Mars, where CO₂, water (ice), and magnesium are abundant. Thus, even though the overall process is non-catalytic, it could serve as a step towards a sustainable CO₂ utilization strategy as well as potentially being a first step towards a magnesium-driven civilization on Mars.

We demonstrated the use of magnesium nanoparticles (and bulk) to convert CO₂ (pure & also from the air) to methane, methanol, formic acid and green cement without external energy within a few minutes, using only water as the sole hydrogen source.

Comparison of Thermal Annealing versus Hydrothermal Treatment Effects on the Detection Performances of ZnO Nanowires

A comparative investigation of the post-electroplating treatment influence on the gas detecting performances of single ZnO nanorod/nanowire (NR/NW), as grown by electrochemical deposition (ECD) and integrated into nanosensor devices, is presented. In this work, hydrothermal treatment (HT) in a H₂O steam and conventional thermal annealing (CTA) in a furnace at 150 °C in ambient were used as post-growth treatments to improve the material properties. Herein, the morphological, optical, chemical, structural, vibrational, and gas sensing performances of the as-electrodeposited and treated specimens are investigated and presented in detail. By varying the growth temperature and type of post-growth treatment, the morphology is maintained, whereas the optical and structural properties show increased sample crystallization. It is shown that HT in H₂O vapors affects the optical and vibrational properties of the material. After investigation of nanodevices based on single ZnO NR/NWs, it was observed that higher temperature during the synthesis results in a higher gas response to H₂ gas within the investigated operating temperature range from 25 to 150 °C. CTA and HT or autoclave treatment showed the capability of a further increase in gas response of the prepared sensors by a factor of ∼8. Density functional theory calculations reveal structural and electronic band changes in ZnO surfaces as a result of strong interaction with H₂ gas molecules. Our results demonstrate that high-performance devices can be obtained with high-crystallinity NWs/NRs after HT. The obtained devices could be the key element for flexible nanoelectronics and wearable electronics and have attracted great interest due to their unique specifications.