{"title":"Tunable oxygen vacancies in CeO2 nanorods via one-step NaBH4-assisted synthesis for enhanced visible-light photocatalytic water splitting","authors":"Srinath Ranjan Tripathy, Saroj Sundar Baral","doi":"10.1007/s40243-026-00359-5","DOIUrl":null,"url":null,"abstract":"<div><p>CeO<sub>2</sub> nanorod photocatalysts with systematically tuned oxygen vacancy concentrations were synthesized via a one-step NaBH<sub>4</sub>-assisted hydrothermal method to elucidate the role of defect engineering in photocatalytic water splitting. A series of reduced samples (Ce1–Ce5) and pristine CeO<sub>2</sub> were thoroughly characterized. Increasing NaBH<sub>4</sub> dosage induced XRD peak broadening with crystallite size reduction (5.37–4.44 nm) and a UV–Vis DRS red shift with bandgap narrowing (2.89–2.72 eV). Urbach energy increased (0.36–0.41 eV), reflecting mid-gap state formation. Raman, FTIR, and EPR (g ≈ 2.002) confirmed rising oxygen vacancy and Ce<sup>3+</sup> content, consistent with XPS, which revealed enhanced oxygen vacancy-related O 1s contribution (16.7–43%) and Ce<sup>3+</sup> fraction. Valence-band XPS and secondary electron cut-off showed band-edge shifts and reduced work function, promoting charge transfer. PL and TCSPC indicated prolonged carrier lifetimes in Ce3 (τ<sub>i</sub> − τ<sub>a</sub> = 1.1087 ns), while Ce4–Ce5 exhibited deep traps. CDB and S-parameter analyses identified Ce3 as optimal, balancing shallow and deep traps for efficient carrier dynamics. BET and BJH confirmed Ce3’s highest surface area (~ 1465 m<sup>2</sup>/g) and mesoporosity. Morphological analysis showed smooth rods (Ce, Ce1) evolving to porous, defect-rich rods (Ce2–Ce3) and partial amorphization (Ce4–Ce5). Ce3 delivered the highest H<sub>2</sub> evolution under visible light without sacrificial agents, highlighting the critical role of controlled oxygen vacancy engineering in advancing CeO<sub>2</sub>-based solar hydrogen production.</p></div>","PeriodicalId":692,"journal":{"name":"Materials for Renewable and Sustainable Energy","volume":"15 1","pages":""},"PeriodicalIF":5.5000,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s40243-026-00359-5.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Materials for Renewable and Sustainable Energy","FirstCategoryId":"1085","ListUrlMain":"https://link.springer.com/article/10.1007/s40243-026-00359-5","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
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Abstract
CeO2 nanorod photocatalysts with systematically tuned oxygen vacancy concentrations were synthesized via a one-step NaBH4-assisted hydrothermal method to elucidate the role of defect engineering in photocatalytic water splitting. A series of reduced samples (Ce1–Ce5) and pristine CeO2 were thoroughly characterized. Increasing NaBH4 dosage induced XRD peak broadening with crystallite size reduction (5.37–4.44 nm) and a UV–Vis DRS red shift with bandgap narrowing (2.89–2.72 eV). Urbach energy increased (0.36–0.41 eV), reflecting mid-gap state formation. Raman, FTIR, and EPR (g ≈ 2.002) confirmed rising oxygen vacancy and Ce3+ content, consistent with XPS, which revealed enhanced oxygen vacancy-related O 1s contribution (16.7–43%) and Ce3+ fraction. Valence-band XPS and secondary electron cut-off showed band-edge shifts and reduced work function, promoting charge transfer. PL and TCSPC indicated prolonged carrier lifetimes in Ce3 (τi − τa = 1.1087 ns), while Ce4–Ce5 exhibited deep traps. CDB and S-parameter analyses identified Ce3 as optimal, balancing shallow and deep traps for efficient carrier dynamics. BET and BJH confirmed Ce3’s highest surface area (~ 1465 m2/g) and mesoporosity. Morphological analysis showed smooth rods (Ce, Ce1) evolving to porous, defect-rich rods (Ce2–Ce3) and partial amorphization (Ce4–Ce5). Ce3 delivered the highest H2 evolution under visible light without sacrificial agents, highlighting the critical role of controlled oxygen vacancy engineering in advancing CeO2-based solar hydrogen production.
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Energy is the single most valuable resource for human activity and the basis for all human progress. Materials play a key role in enabling technologies that can offer promising solutions to achieve renewable and sustainable energy pathways for the future.
Materials for Renewable and Sustainable Energy has been established to be the world''s foremost interdisciplinary forum for publication of research on all aspects of the study of materials for the deployment of renewable and sustainable energy technologies. The journal covers experimental and theoretical aspects of materials and prototype devices for sustainable energy conversion, storage, and saving, together with materials needed for renewable fuel production. It publishes reviews, original research articles, rapid communications, and perspectives. All manuscripts are peer-reviewed for scientific quality.
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1. MATERIALS for renewable energy storage and conversion: Batteries, Supercapacitors, Fuel cells, Hydrogen storage, and Photovoltaics and solar cells.
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