Abstract
The friction between nanomaterials and Teflon magnetic stirring rods has recently drawn much attention for its role in dye degradation by magnetic stirring in dark. Presently the friction between TiO2 nanoparticles and magnetic stirring rods in water has been deliberately enhanced and explored. As much as 1.00 g TiO2 nanoparticles were dispersed in 50 mL water in 100 mL quartz glass reactor, which got gas-closed with about 50 mL air and a Teflon magnetic stirring rod in it. The suspension in the reactor was magnetically stirred in dark. Flammable gases of 22.00 ppm CO, 2.45 ppm CH4, and 0.75 ppm H2 were surprisingly observed after 50 h of magnetic stirring. For reference, only 1.78 ppm CO, 2.17 ppm CH4, and 0.33 ppm H2 were obtained after the same time of magnetic stirring without TiO2 nanoparticles. Four magnetic stirring rods were simultaneously employed to further enhance the stirring, and as much as 30.04 ppm CO, 2.61 ppm CH4, and 8.98 ppm H2 were produced after 50 h of magnetic stirring. A mechanism for the catalytic role of TiO2 nanoparticles in producing the flammable gases is established, in which mechanical energy is absorbed through friction by TiO2 nanoparticles and converted into chemical energy for the reduction of CO2 and H2O. This finding clearly demonstrates a great potential for nanostructured semiconductors to utilize mechanical energy through friction for the production of flammable gases.
Highlights
Mechanical energy is abundant in ambient environments and is widely harvested as electricity on large scale through hydroelectric generation, wind power generation, and tidal power generation, etc
These results clearly demonstrate that through friction, mechanical energy of low-frequency motions can be effectively converted by some nanomaterials to chemical energy, which has been termed as tribocatalysis [17] and should be highly interesting from the viewpoint of harvesting mechanical energy in ambient environments
As a matter of fact, TiO2 nanoparticles are usually magnetically stirred in photocatalytic experiments, in which they are stable in themselves in the course of magnetic stirring and can be used repeatedly
Summary
Mechanical energy is abundant in ambient environments and is widely harvested as electricity on large scale through hydroelectric generation, wind power generation, and tidal power generation, etc. As ultrasonic vibrations are not common in ambient environments, piezocatalysis driven by low-frequency motions should be explored from the viewpoint of energy harvest [12] For this reason, magnetic stirring has often been adopted to stimulate piezoelectric nanomaterials for piezocatalysis. As the friction between nanoparticles and Teflon magnetic stirring rods can be dramatically enhanced through increasing contents of nanoparticles and through employing multiple magnetic stirring rods simultaneously, highly accelerated degradation of organic dyes has been observed for BST nanoparticles [17], BiOIO3 nanoparticles [18], zinc oxide nanorods [19], CdS nanowires [20], and Bi2WO6 nanoflowers [21] under magnetic stirring These results clearly demonstrate that through friction, mechanical energy of low-frequency motions can be effectively converted by some nanomaterials to chemical energy, which has been termed as tribocatalysis [17] and should be highly interesting from the viewpoint of harvesting mechanical energy in ambient environments. The finding in this study as well as those previous ones should suggest a great potential for nanostructured semiconductors to harvest mechanical energy through friction for environmental governing and clean energy production
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