Abstract
Massive industrial and agricultural developments have led to adverse effects of environmental pollution resisting conventional treatment processes. The issue can be addressed via heterogeneous photocatalysis as witnessed recently. Herein, we have developed novel metal/semi-conductor/polymer nanocomposite for the catalyzed degradation and mineralization of model organic dye pollutants in darkness. RuO2-TiO2 mixed oxide nanoparticles (NPs) were modified with diphenyl amino (DPA) groups from the 4-diphenylamine diazonium salt precursor. The latter was reduced with ascorbic acid to provide radicals that modified the NPs and further served for in situ synthesis of polyaniline (PANI) that resulted in RuO2/TiO2-DPA-PANI nanocomposite catalyst. Excellent adhesion of PANI to RuO2/TiO2-DPA was noted but not in the case of the bare mixed oxide. This stresses the central role of diazonium compounds to tether PANI to the underlying mixed oxide. RuO2-TiO2/DPA/PANI nanocomposite revealed superior catalytic properties in the degradation of Methyl Orange (MO) compared to RuO2-TiO2/PANI and RuO2-TiO2. Interestingly, it is active even in the darkness due to high PANI mass loading. In addition, PANI constitutes a protective layer of RuO2-TiO2 NPs that permitted us to reuse the RuO2-TiO2/DPA/PANI nanocomposite nine times, whereas RuO2-TiO2/PANI and RuO2-TiO2 were reused seven and five times only, respectively. The electronic displacements at the interface of the heterojunction metal/semi-conductor under visible light and the synergistic effects between PANI and RuO2 result in the separation of electron-hole pairs and a reduction of its recombination rate as well as a significant catalytic activity of RuO2-TiO2/DPA/PANI under simulated sunlight and in the dark, respectively.
Highlights
The development of photocatalytic materials that are active both under visible light and in the dark constitute the subject of numerous studies targeted for environmental applications [1]
RuO2 -TiO2 /PANI nanocomposites were prepared in four steps: (i) sol-gel synthesis of TiO2 followed by (ii) RuO2 doping, the mixed oxide was (iii) grafted with diphenyl amino (DPA)
A novel catalytic support based on RuO2 -TiO2 mixed oxide NPs coated PANI was prepared by in situ oxidative polymerization of aniline on diazonium-modified RuO2 -TiO2 heterostructure
Summary
The development of photocatalytic materials that are active both under visible light and in the dark constitute the subject of numerous studies targeted for environmental applications [1]. Titanium dioxide (TiO2 ) has attracted much attention due to its great potential applications and its physico-chemical and catalytic properties [2,3,4,5] It is a multifunctional semiconductor and one of the most promising materials for heterogeneous photocatalysis under UV irradiation. Catalysts 2019, 9, 578 of visible light [6,7,8,9] In this challenging context, efforts have been focused on the development of new materials with a lower electron-hole pair recombination rate and a strong absorption of sunlight. Efforts have been focused on the development of new materials with a lower electron-hole pair recombination rate and a strong absorption of sunlight This involves combining the TiO2 with another material that has a narrow band gap [10]. RuO2 and TiO2 have the same tetravalent cations; the different electron configurations between Ti and Ru create different physico-chemical properties in the oxides
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