Graphene-TiO2 hybrids for photocatalytic aided removal of VOCs and nitrogen oxides from outdoor environment

abstract

Outdoor and indoor air pollution has become a global concern in modern society. Although many policies and regulations on air quality have been promulgated worldwide over the past decades, airborne pollution still negatively affects health and therefore the life-style of human beings. One of the strategies to challenge this problem might be reducing the amount of airborne pollutant by mineralising them via photoinduced reactions. Photocatalytic oxidation of gaseous pollutants via titanium dioxide is one of the most promising solar photochemical reactions. In this research work, by means of a green sol-gel procedure, we have coupled titania to graphene (0.5 and 1.0 wt%) aiming to increase the solar photocatalytic activity of the produced hybrid materials. Transient paramagnetic species formed upon UV-A irradiation were detected by means of EPR spectroscopy. The photocatalytic reactions were assessed by monitoring the removal of nitrogen oxides and two different volatile organic compounds (benzene and isopropanol), which has never been assessed before. Our results highlight the exceptional characteristics of the TiO2/graphene hybrid material synthesised with 1.0 wt% graphene, and its excellent suitability for multi-purpose applications in the field of environmental remediation. Compared to unmodified titania, it shows a clear enhancement in the photocatalytic removal of those hazardous pollutants, having a photocatalytic degradation rate twice higher. In addition, the same material is highly stable and shows fully recyclability over repeated tests. Hybrid titania-graphene materials could thus be exploited to grant safer outdoor and indoor environments, having thus a beneficial impact on public health and on the quality of our lives.

subject category

Engineering, Environmental; Engineering, Chemical

authors

Tobaldi, DM; Dvoranova, D; Lajaunie, L; Rozman, N; Figueiredo, B; Seabra, MP; Skapin, AS; Calvino, JJ; Brezova, V; Labrincha, JA

Groups

G4 - Renewable Materials and Circular Economy

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Graphenest’s New Engineered System and its Implementation Solutions (GNESIS)

acknowledgements

This work was partly developed within the scope of the bilateral project between Portugal and the Slovak Republic, FCT/484/15/01/2019/S and in the frame of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. This study was also financially supported by Scientific Grant Agency of the Slovak Republic (VEGA Project 1/0026/18) and Slovak Research and Development Agency under the contract No. SK-PT-2018-0007. David Maria Tobaldi is overly grateful to FCT and to Portuguese national funds (OE), through FCT, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19. This project has also received partial funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 823717 -ESTEEM3. Luc Lajaunie gratefully acknowledges the support from the Spanish Ministerio de Economia y Competitividad (PID2019-107578GA-I00). Authors wish to thank the European Structural and Investment Funds in the FEDER component, through the Operational Programme for Competitiveness and Internationalization (COMPETE 2020) under the Project GNESIS Graphenest's New Engineered System and its Implementation Solutions -Funding Reference: POCI-01-0247-FEDER-033566, European Regional Development Fund. Nejc Rozman and Andrijana Sever Skapin acknowledge the financial support provided by the Slovenian Research Agency (grant No. NC-0002 and No. P2-0273), and Slovenian Ministry of Education, Science and Sport for funding through the Promotion of the employment of young PhDs program. We are very much obliged to Miss Dafne Maria Glaglanon for proof-editing the English of the manuscript.