RESUMO
Cathodic CO2 adsorption and activation is essential for high-temperature CO2 electrolysis in solid oxide electrolysis cells (SOECs). However, the component of oxygen ionic conductor in the cathode displays limited electrocatalytic activity. Herein, stable single Ruthenium (Ru) atoms are anchored on the surface of oxygen ionic conductor (Ce0.8 Sm0.2 O2-δ , SDC) via the strong covalent metal-support interaction, which evidently modifies the electronic structure of SDC surface for favorable oxygen vacancy formation and enhanced CO2 adsorption and activation, finally evoking the electrocatalytic activity of SDC for high-temperature CO2 electrolysis. Experimentally, SOEC with the Ru1 /SDC-La0.6 Sr0.4 Co0.2 Fe0.8 O3-δ cathode exhibits a current density as high as 2.39â A cm-2 at 1.6â V and 800 °C. This work expands the application of single atom catalyst to the high-temperature electrocatalytic reaction in SOEC and provides an efficient strategy to tailor the electronic structure and electrocatalytic activity of SOEC cathode at the atomic scale.
RESUMO
In proton exchange membrane fuel cells (PEMFCS), a Pt-based catalyst has been plagued by activity and durability, making it difficult to implement in large-scale commercial applications. In this paper, a composite material formed by titanium dioxide and carbon black containing oxygen vacancies (TiO2(OV)-C) was used as a functional support to successfully load Pt nanoparticles (NPS). The introduction of oxygen vacancies induces the formation of a connection between Pt and TiO2, which not only strengthens the fixation of Pt by the composite support but also optimizes the local charge density of Pt. Compared with Pt/C (0.842 V) and Pt/TiO2-C (0.841 V), the half-wave potential (E1/2) of Pt/TiO2(OV)-C (0.862 V) is increased by 20 mV and 21 mV, respectively. After a long-term durability test, the E1/2 of Pt/TiO2(OV)-C is only attenuated by 5 mV. In addition, the mass activity (MA) and specific activity (SA) decreased from 183.4 mA mg-1 and 0.565 mA cm-2 to 144.4 mA mg-1 and 0.483 mA cm-2 at 0.85 V, only decreasing by 21% and 17 %, showing good stability. X-ray photoelectron spectroscopies (XPS) and density functional theory (DFT) calculations show that the interaction between Pt and TiO2 reduces the d-band center of Pt, thereby improving the desorption of intermediates *OH, which in turn promotes the activity of alkaline ORR. This study not only shows that OV plays a key role in the process of inducing interaction, but also deeply studies the influence of this interaction on the active site Pt, which provides more choices for the design of excellent multiphase catalysts.
RESUMO
Recently, the use of semiconductor-based photocatalytic technology as an effective way to mitigate the environmental crisis attracted considerable interest. Here, the S-scheme BiOBr/CdS heterojunction with abundant oxygen vacancies (Vo-BiOBr/CdS) was prepared by the solvothermal method using ethylene glycol as a solvent. The photocatalytic activity of the heterojunction was investigated by degrading rhodamine B (RhB) and methylene blue (MB) under 5 W light-emitting diode (LED) light. Notably, the degradation rate of RhB and MB reached 97% and 93% in 60 min, respectively, which were better than that of BiOBr, CdS, and BiOBr/CdS. It was due to the construction of the heterojunction and the introduction of Vo, which facilitated the spatial separation of carriers and enhanced the visible-light harvest. The radical trapping experiment suggested that superoxide radicals (·O2-) acted as the main active species. Based on valence balance spectra, Mott-Schottky(M-S) spectra, and DFT theoretical calculations, the photocatalytic mechanism of the S-scheme heterojunction was proposed. This research provides a novel strategy for designing efficient photocatalysts by constructing S-scheme heterojunctions and introducing oxygen vacancies for solving environmental pollution.
