Tailoring oxygen vacancies in ThO2 for improved light emission and ORR electrocatalysis

The role of defects in multifunctional materials and defect engineering are fascinating to scientific com-munity. To understand the role of oxygen vacancies in photoluminescence (PL) and oxygen reduction re-action (ORR), thoria samples were prepared with Eu3+ doping and Nb5+ codoping. The positron annihilation lifetime spectroscpy (PALS) showed the increase in the oxygen vacancies in thoria upon trivalent Eu3+ doping and their removal upon codoping with Nb5+. This is in concordance with increase in nearest oxygen neighbours to Eu3+ and Th4+ upon Nb5+ codoping as revealed by Extended X-ray Ab-sorption Fine Structure (EXAFS). Oxygen vacancy removal on Nb5+ codoping manifested in restoration of symmetry around Eu3+ and enhanced photoluminescence (PL) intensities giving very bright red emission while the oxygen vacancy rich thoria samples aided the electrochemical ORR. The studies showed that the concentration of the oxygen vacancies can be tuned upon the judicious choice and concentration of the aliovalent dopant and codopant depending on the envisaged functionality of the material. & COPY; 2023 Elsevier Ltd. All rights reserved.

Automated summary

The role of defects in multifunctional materials and defect engineering is intriguing. Oxygen vacancies in thoria samples were found to play a role in photoluminescence (PL) and oxygen reduction reaction (ORR) with the introduction of Eu3+ doping and removal upon codoping with Nb5+. The concentration of oxygen vacancies can be adjusted by the choice and concentration of aliovalent dopant and codopant to determine the desired functionality of the material.