Impacts of oxygen vacancies on the electrocatalytic activity of AuTiO2 nanocomposites towards oxygen reduction

Abstract

Functional nanocomposites based on gold nanoparticles deposited onto TiO 2 colloids were prepared by a simple wet chemistry method, and subject to hydrothermal treatment at a controlled temperature in the presence of ascorbic acid. Transmission electron microscopic measurements showed that the gold nanoparticles (10-30 nm in diameter) were embedded within the TiO 2 matrix consisting of colloids of 5-10 nm in diameter and anatase crystalline structures, as evidenced in x-ray diffraction studies. Interestingly, electron paramagnetic resonance measurements showed the formation of oxygen vacancies after hydrothermal treatment and the concentrations of oxygen vacancies increased with the amount of ascorbic acid added. Consistent results were obtained in x-ray photoelectron spectroscopic measurements, which suggested partial charge transfer from gold to oxygen-deficient TiO 2. The Au:Ti atomic ratio in the nanocomposites was estimated to be ca. 11% and consistent among the series of samples. Electrochemically, the nanocomposites exhibited apparent electrocatalytic activity towards oxygen reduction reactions in alkaline media, which showed a peak-shaped variation with the concentration of the oxygen vacancies. This was accounted for by the deliberate manipulation of the binding energy of oxygen species onto the nanocomposite surfaces. In addition, the AuTiO 2

Photocatalytic hydrogen evolution by co-catalyst-free TiO2/C bulk heterostructures synthesized under mild conditions

“…As suggested by a sharper slope change, SA1 apparently comprises two components with different relaxation rates, which are not observed for A1. The dependence on microwave power of the intensity of signals associated with oxygen vacancy defects in TiO 2 was described either as reaching a plateau 46 or decreasing aer a maximum, 53 indicating relatively long relaxation times for these radicals. The latter trend was also attributed to unpaired electrons in a point defect at the interface between particles.…”

In Situ Formation of Surface-Induced Oxygen Vacancies in Co9S8/CoO/NC as a Bifunctional Electrocatalyst for Improved Oxygen and Hydrogen Evolution Reactions

“…In spite of this distinctiveness, their poor intrinsic electronic conductivity and inferior bifunctionality for overall electrochemical water splitting have hindered their practical applications [22,23]. To resolve its intrinsic conductivity issue, it was reported while creating oxygen vacancies in these oxides has altered the electronic environment that acted critically to induce conductivity [24][25][26]. Xu et al has fabricated plasma-engraved oxygen vaccines in Co 3 O 4 nanosheets and reported its improved OER performance (η of 300 mV at J OER = 10 mA cm −2 ) over pristine Co 3 O 4 nanosheets (η of 540 mV at J OER = 10 mA cm −2 ).…”

Ethanol Oxidation Reaction Catalyzed by Palladium Nanoparticles Supported on Hydrogen‐Treated TiO2 Nanobelts: Impact of Oxygen Vacancies

“…Yet, a well‐defined resonance emerged at ca . 3370 G after hydrogen treatment, and the resonance became increasingly intensified with increasing thermal treatment temperature from 400 to 600 °C (aqua blue, magenta, and blue curves), with the corresponding g value estimated to be 2.001 . A similar profile was observed without the deposition of Pd nanoparticle (green curve).…”