NiO has been found to be highly outstanding in producing H2 and O2 from H2O through magnetic stirring, while its capability for the reduction of CO2 through mechanical stimulation has not been investigated. Presently, NiO particles have been employed to promote the conversion of H2O and CO2 enclosed in reactors into flammable gases through magnetic stirring. For a 150 mL glass reactor filled with 50 mL water, 1.00 g of NiO particles, and 1 atm of CO2, 24 h of magnetic stirring using a home-made Teflon magnetic rotary disk resulted in the formation of 33.80 ppm CO, 10.10 ppm CH4, and 12,868.80 ppm H2. More importantly, the reduction of CO2 was found to be substantially enhanced through coating some polymers and metals on the reactor bottoms, including 25.64 ppm CO and 70.97 ppm CH4 obtained for a PVC-coated reactor and 30.68 ppm CO, 52.78 ppm CH4, 3.82 ppm C2H6, and 2.18 ppm C2H4 obtained for a stainless steel-coated reactor. Hydroxyl radicals were detected using fluorescence spectroscopy for NiO particles under magnetic stirring in water. A tribo-catalytic mechanism has been proposed for the conversion of H2O and CO2 into flammable gases by NiO particles under magnetic stirring that is based on the excitation of electron-hole pairs in NiO by mechanical energy absorbed through friction. These findings not only reveal a great potential for mechanical energy to be utilized for CO2 conversion but are also valuable for fundamental studies.

Copper rotary disks were fabricated through mounting copper disks and magnets on opposite surfaces of Teflon disks separately, and quartz glass reactors (150 mL) were modified through covering their bottoms with Al 2 O 3 , copper, and titanium disks separately. For a glass-bottomed reactor placed with a copper rotary disk and filled with 50 mL water and 1 atm CO 2 , flammable gases of 670.96 ppm H 2 , 22.21 ppm CO, 3.98 ppm CH 4 , 0.96 ppm C 2 H 4 , and 0.66 ppm C 2 H 6 were surprisingly produced after the copper rotary disk was driven to rotate for 5 h; flammable gases were obtained in comparable amounts for reactors with Al 2 O 3 , copper, and titanium bottoms separately. A tribo-catalytic mechanism has been proposed, in which water at micro-holes in friction surfaces is squeezed by elastically deformed copper of rotating copper disks, and under increased pressure CO 2 and H 2 O are catalyzed to react to form flammable gases by copper.

X-ray detectors based on conventional semiconductors with large atomic numbers are suffering from the poor stability under a high dose rate of ionizing irradiation. In this work, we demonstrate that a wide band gap ceramic–boron nitride with small atomic numbers could be used for sensitive X-ray detection. Boron nitride samples showed excellent resistance to ionizing radiation, which have been systematically studied with the neutron- and electron-aging experiments. Then, we fully analyzed the influence of these aging effects on the fundamental properties of boron nitride. Interestingly, we found that the boron nitride samples could maintain relatively good charge transport properties even after large dose of neutron irradiation. The fabricated X-ray detectors showed decent performance metrics, and the neutron-aged boron nitride even showed improved operational stability under continuous X-ray irradiation, suggesting the great potential for real applications.

More and more metal oxide nanomaterials are being synthesized and investigated for degradation of organic pollutants through harvesting friction energy, yet the strategy to optimize their performance for this application has not been carefully explored up to date. In this work, three commercially available ZnO powders are selected and compared for tribocatalytic degradation of organic dyes, among which ZnO-1 and ZnO-2 are agglomerates of spherical nanoparticles around 20 nm, and ZnO-3 are particles of high crystallinity with a regular prismatic shape and smooth surfaces, ranging from 50 to 150 nm. Compared with ZnO-1 and ZnO-2, ZnO-3 exhibits a much higher tribocatalytic degradation performance, and a high degradation rate constant of 6.566 × 10−2 min−1 is achieved for RhB, which is superior compared with previous tribocatalytic reports. The stability and universality of ZnO-3 were demonstrated through cycling tests and degradation of different types of dyes. Furthermore, the mechanism of tribocatalysis revealed that h+ was the main active species in the degradation process by ZnO. This work highlights the great significance of high crystallinity rather than a large specific surface area for the development of high-performance tribocatalysts and demonstrates the great potential of tribocatalysis for water remediation.