Wanping Chen’s research while affiliated with Wuhan University and other places

Coating disk-shaped materials on the bottoms of containers has become a highly effective method for tribocatalysis enhancement. Here, the effects of Ti coatings on the tribocatalytic degradation of organic dyes by CdS nanoparticles were systematically studied. For both 50 mg/L rhodamine B (RhB) and 20 mg/L methyl orange (MO) solutions, the tribocatalytic degradation by CdS nanoparticles was dramatically enhanced in Ti-coated beakers compared to as-received glass-bottomed beakers, with the degradation rate constant increased by 4.77 and 5.21 times, respectively. Moreover, for tribocatalytic degradation of MO using CdS, two quite different MO degradation modes were identified between Ti and Al2O3 coatings. Electron paramagnetic resonance (EPR) spectroscopy analyses showed that more radicals were generated when CdS nanoparticles rubbed against the Ti coating than against the glass bottom, and boron nitride nanoparticles were employed to verify that the enhancement associated with the Ti coating resulted from the interactions between Ti and CdS. These findings underscore the importance of catalyst and coating material selection in tribocatalytic systems, offering valuable insights for the development of efficient environmental purification technologies.

Pt–SnO2 composite nanoceramics recently have drawn much attention for their strong responses to CO at room temperature and a remarkable long-term stability. To further improve their microstructure and performance, in this study, a solution reduction Pt-loading method was used to deposit Pt nanoparticles (~ 5 nm) on SnO2 nanoparticles, from which Pt–SnO2 composite nanoceramics were prepared through pressing and sintering. Not only a much improved Pt distribution was revealed for the nanoceramics according to field emission scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy analyses, their room-temperature responses to CO were also greatly enhanced. To 0.04% CO–20%O2–N2, a room-temperature response as high as 2427 was obtained for 1 wt% Pt–SnO2 composite nanoceramics, which was increased by more than 20 times from that shown by Pt–SnO2 composite nanoceramics prepared previously. A room-temperature CO-sensing mechanism has been first established for Pt–SnO2 system, in which Pt catalyzes not only the chemisorption of oxygen molecules on SnO2 at room temperature but also the reaction between CO and chemisorbed oxygen at room temperature. These results clearly demonstrate a promising prospect for Pt–SnO2 composite nanoceramics in realizing reliable and convenient CO detection.

Coating disk-shaped materials on the bottoms of containers has become a highly effective method for tribocatalysis enhancement. Presently, the effects of Ti coatings on the tribocatalytic degradation of organic dyes by CdS nanoparticles have been systematically studied. For both 50 mg/L rhodamine B (RhB) and 20 mg/L methyl orange (MO) solutions, the tribocatalytic degradation by CdS nanoparticles was dramatically enhanced in Ti-coated beakers than in as-received glass-bottomed beakers, with the degradation rate constant increased by 4.77 and 5.21 times, respectively. Moreover, for tribocatalytic degradation of MO using CdS, two quite different MO degradation modes have been identified between Ti and Al2O3 coatings. Electron paramagnetic resonance (EPR) spectroscopy analyses showed that more radicals were generated when CdS nanoparticles rubbed against Ti coating than glass bottom, and boron nitride nanoparticles had been employed to verify that the enhancement associated with Ti coatings resulted from the interactions between Ti and CdS. These findings underscore the importance of catalysts and coating materials selection in tribocatalytic systems, offering valuable insights for the development of efficient environmental purification technologies.

As a newly emerging catalysis, tribocatalysis is receiving more and more attention with regard to the criteria to fabricate or choose materials as catalysts for it. In this study, two different commercial silicon (Si) powders, Si30 and Si300, were adopted as catalysts in tribocatalytic degradation of organic dyes. Only round nanoparticles from 30 to 100nm were observed in Si30, while some highly large and irregular particles, as large as 1000nm × 500nm and with a roughly flat major surface, could be observed in Si300. Stimulated through magnetic stirring using Teflon magnetic rotary disks, as much as 95% of 20 mg/L rhodamine B (RhB) solution and 97% of 20 mg/L methyl orange (MO) solution were degraded by Si300 after 3h and 50min, respectively; while only 73% of RhB and 83% of MO were degraded by Si30 after 5h and 4h, respectively. EPR spectra showed that more superoxide and hydroxyl radicals were generated by Si300 under magnetic stirring. It is proposed that in those large particles in Si300, their large flat major surfaces dramatically enhance their absorption of mechanical energy through friction and there are much less lattice defects to hinder electrons and holes from diffusing to the surface, which both results in the contrasting tribocatalytic degradations of organic dyes between Si300 and Si30. These findings reveal a huge difference in tribocatalytic performance among different materials of the same composition.

Balancing the piezoelectric coefficient and carrier concentration of materials is key in the field of piezocatalysis. In this work, Bi2WO6 material with both piezoelectric and semiconductor properties was chosen as a model material. A one-step ethylene glycol (EG)-assisted solvothermal method was used to synthesize Bi2WO6 with oxygen vacancies. By controlling the solvothermal time and temperature, the oxygen vacancy concentration (COV) was regulated. As COV increases, the piezoelectric coefficient decreases, the carrier concentration increases, and the hydrogen production rate first increases but then decreases. When COV reaches 1.45×10¹² spins·mg⁻¹, the corresponding piezoelectric coefficient and carrier concentration are 13.9 pm·V⁻¹ and 2.90×10²⁰ cm⁻³, respectively. The optimal hydrogen production rate per power of 2.21 μmol·g⁻¹·h⁻¹·W⁻¹ is equivalent to or even better than that of most reported piezocatalysts. The piezoelectric coefficient and carrier concentration, as two factors, jointly determine the piezocatalytic performance. The findings of this research can provide important and deep-seated insights for better piezocatalysts in the future.

With a band gap of 2.4 eV, CdS has been extensively explored for photocatalytic applications under visible light irradiation. In this study, CdS nanoparticles have been investigated for the tribocatalytic degradation of concentrated Rhodamine B (RhB) and methyl orange (MO) solutions. For CdS nanoparticles in a glass beaker, 78.9% of 50 mg/L RhB and 69.8% of 20 mg/L MO solutions were degraded after 8 h and 24 h of magnetic stirring using Teflon magnetic rotary disks, respectively. While for CdS nanoparticles in a beaker with Al2O3 coated on its bottom, 99.8% of the RhB solution was degraded after 8 h of magnetic stirring and 95.6% of the MO solution was degraded after 12 h of magnetic stirring. Moreover, another contrast was observed between the two beaker bottoms—a new peak at 250 nm in UV–visible absorption spectra was only observed for the MO degradation by CdS in the as-received glass beaker, which indicates that MO molecules were only broken into smaller organic molecules in that case. These findings are meaningful for expanding the catalytic applications of CdS and for achieving a better understanding of tribocatalysis as well.

Triboelectrification, a process that transforms mechanical energy into electrical energy through friction, holds promise for eco-friendly wastewater treatment. This study delves into the enhancement of tribocatalytic dye degradation using SrTiO3, a material notable for its non-piezoelectric and centrosymmetric properties. The synthesis of uni- and bi-doped SrTiO3 particles, achieved through a solid-state reaction at 1000 °C, results in a high-purity cubic perovskite structure. Doping with rhodium (Rh) and carbon (C) causes crystal lattice contraction, internal stress, and significant oxygen vacancies. These changes notably improve tribocatalytic efficiency under solar irradiation, with Rh-doped SrTiO3 demonstrating an impressive degradation rate of approximately 88% for Rhodamine B (RhB), along with reaction rate constants near 0.9 h⁻¹ at 554 nm and a noticeable blueshift. This study highlights that defects introduced by doping are integral to this process, boosting catalytic activity through energy state modification and enhancing surface redox radical production. Additionally, these defects are instrumental in generating a flexoelectric field, which markedly influences the separation of electron–hole pairs under solar irradiation. Our findings illuminate the complex interplay between material composition, defect states, and environmental conditions, paving the way for advanced strategies in environmental remediation through optimized tribocatalytic activity.

GaN is more stable than most metal oxide semiconductors for the photocatalytic degradation of organic pollutants in harsh conditions, while its catalytic efficiency has been difficult to be substantially improved. In this study, the tribocatalytic degradation of organic dyes by GaN nanoparticles has been investigated. Stimulated through magnetic stirring using homemade Teflon magnetic rotary disks in glass beakers, the GaN nanoparticles were found to induce negligible degradation in rhodamine B (RhB) and methyl orange (MO) solutions. Surprisingly, the degradation was greatly enhanced in beakers with Ti and Al2O3 coatings on their bottoms: 99.2% and 99.8% of the 20 mg/L RhB solutions were degraded in 3 h for the Ti and Al2O3 coatings, respectively, and 56% and 60.2% of the 20 mg/L MO solutions were degraded in 24 h for the Ti and Al2O3 coatings, respectively. Moreover, the MO molecules were only broken into smaller organic molecules for the Ti coating, while they were completely degraded for the Al2O3 coating. These findings are important for the catalytic degradation of organic pollutants by GaN in harsh environments and for achieving a better understanding of tribocatalysis as well.

The Curie point of barium titanate (BaTiO3) has been a focal point of research since the discovery of its ferroelectric properties. Exploring methods to elevate the Curie point without relying on Pb as a dopant presents fresh opportunities for lead-free dielectric and/or piezoelectric materials. It is essential to avoid introducing ions like K+ and Na+, which could jeopardize the functional ceramic characteristics. This study delves into the stoichiometry of barium titanate, examining how impurities, point defects and doping techniques influence its Curie point, focus on the potential of doping and processing to enhance this property. BaTiO3 nanopowders were synthesized directly with varying Ba:Ti ratios in an ethanol–water solution at 60∘C, followed by sintering at 1280∘C and characterization through dielectric spectroscopy. A comparison was made with samples doped with Si, vapor-doped with Bi and vapor-doped with Pb. Results revealed that even minimal Si doping could boost the ferroelectric properties and elevate the Curie point, while vapor-doping with trace amounts of PbO or Bi2O3 significantly increased the Curie point, particularly in samples with higher Ti content. The impact of vapor dopants of PbO and Bi2O3 was similar, with a nominal doping level of 1mol% shifting the Curie point above 140∘C. Notably, in samples with a Ba:Ti ratio of 0.95 vapor-doped with PbO, the Curie point rose to 146∘C, a notable increase of 16∘C, surpassing the traditional doping efficiency. This study offers fresh insights into enhancing the Curie point of barium titanate-based materials, exploring the intricate connections among chemical stoichiometry, dopants, point defects and dielectric properties. It highlights the significant influence of chemical composition, impurities, defects and doping strategies on the dielectric characteristics of barium titanate.