Reduction of CO2 by TiO2 nanoparticles through friction in water

Abstract

The friction between some nanomaterials and teflon magnetic stirring rods has recently been found responsible for dye degradation by magnetic stirring in dark. In this work, a study is conducted on the reduction of CO₂ by TiO₂ nanoparticles under magnetic stirring in water. In a 100-mL reactor filled with 50-mL water, 1.00-g TiO₂ nanoparticles and 1-atm CO₂, 50-h magnetic stirring results in the formation of 6.65 × 10^–6 (volume fraction) CO, 2.39 × 10^–6 CH₄ and 0.69 × 10^–6 H₂; while in a reactor without TiO₂ nanoparticles, the same magnetic stirring leads only 2.22 × 10^–6 CO and 0.98 × 10^–6 CH₄ to form. Four magnetic stirring rods are used simultaneously to further enhance the stirring, and 50-h magnetic stirring can form 19.94 × 10^–6 CO, 2.33 × 10^–6 CH₄, and 2.06 × 10^–6 H₂. A mechanism for the catalytic role of TiO₂ nanoparticles in the reduction of CO₂ and H₂O is established, which is based on the excitation of electron-hole pairs in TiO₂ by mechanical energy absorbed through friction. This finding clearly demonstrates that nanostructured semiconductors are able to utilize mechanical energy obtained through friction to reduce CO₂, thus providing a new direction for developing and utilizing the mechanical energy harvested from ambient environment.