Photocatalytic reduction of levulinic acid using thermally modified niobic acid

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-12, Vol.450, p.137935, Article 137935
• Main Authors: Filho, José B.G., Gomes, Gustavo H.M., Silva, Ingrid F., Rios, Regiane D.F., Victória, Henrique F.V., Krambrock, Klaus, Pereira, Marcio C., Oliveira, Luiz C.A.
• Format: Article
• Language: English
• Subjects: Biomass conversion; Niobium oxide; Oxide defects; Oxygen vacancies; Photocatalysis; Structural defects
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.137935

[Display omitted] •The niobic acid HY-340 was thermally modified at 200 °C, 400 °C and 600 °C.•These materials were applied in the photocatalytic reduction of levulinic acid.•The best performance was obtained by the photocatalyst synthesized at 600 °C.•Oxygen vacancies were made in this same Nb2O5 and further improved its activity.•The properties of photocatalysts with and without vacancies were studied in depth. After the discovery that commercial niobic acid (H0) is able to reduce the levulinic acid in value added molecules, H0 was thermally treated at 200 °C, 400 °C, and 600 °C, generating the niobium oxides H1, H2 and H3 and the photocatalytic improvement towards reduction was investigated. Although the higher temperatures significantly decreased the specific surface area, it was important to remove surface hydroxyl groups and create the T and TT-Nb2O5 phase mixture in H3 which were responsible for its best performance (36.4% of conversion and almost 99% of selectivity for reduced products). To further improve the H3 photoactivity, an identical synthesis was performed in H2 flow to produce oxygen vacancies in the structure of the new photocatalyst (H3OV). This simple modification method increased ∼7% of products yield, which is the best photocatalytic result obtained for pure niobium oxides so far, and proved that it is possible to significantly increase photocatalytic performance without laborious modifications. The electronic and structural differences between H3 and H3OV were investigated by XRD Rietveld refinement, EPR, HR-TEM, DRS and SAED analyses.