Copper-doped ZrO2 nanoparticles as high-performance catalysts for efficient removal of toxic organic pollutants and stable solar water oxidation

doi:10.1016/j.jenvman.2020.110088

Journal of Environmental Management

Volume 260, 15 April 2020, 110088

https://doi.org/10.1016/j.jenvman.2020.110088 Get rights and content

Highlights

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Doping effect on efficient removal of organic dyes and the PEC water splitting are reported.
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The band gap values reduced from 5.02 to 2.1 eV as the doping concentration increased.
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The optimal doped sample achieved 90% methyl orange dye degradation under solar light.
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The EIS analysis revealed the optimal doped sample exhibited the lower charge resistance.
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The optimal photocatalysts showed 50-fold enhancement in photocurrent density over pure sample.

Abstract

Doping effect on the photoelectrochemical (PEC) water splitting efficiency and photocatalytic activities of ZrO₂ under visible light are reported. The XRD analysis revealed that pure, 0.1 and 0.3 mol% doped samples showed mixed crystal phases (tetragonal and monoclinic) and 0.5 mol% doped sample showed a pure tetragonal phase. Under visible light, 90% of methyl orange dye degradation was achieved with in 100 min. Moreover, the optimal doped sample showed a significant degradation rate constant over other samples. The doped photoelectrodes display a better PEC water oxidation performance over pure photoelectrode. Furthermore, the optimal doped (0.3 mol %) electrode shows 0.644 mAcm⁻² photocurrent density, corresponding to an approximate 50-fold enhancement over pure electrode (0.013 mAcm⁻²). The optimized doped sample achieved 98% degradation of methyl orange within 100 min of light irradiation. The superior PEC water oxidation and photocatalytic activity of optimal doped samples under visible light are credited to suitable doping content, crystalline size, greater surface area, suitable bandgap, a lower charge carrying resistance, surface properties and the ability for decreasing the charge carrier's recombination rate.

Introduction

In recent years, the goal of scientific research community is to develop renewable energy and clean power source that fulfil the severe issues of energy shortage and environmental deterioration (Liu et al., 2019a, Reddy et al., 2019, Mazur et al., 2018). The photoelectrochemical (PEC) conversion of water into hydrogen energy and CO₂ reduction into chemical energy using a solar light has involved significant attention (Roger et al., 2017, Song et al., 2016). Moreover, the greatest benefit for PEC activity is the active combination of solar energy transformation and electrolysis of water on a photoelectrode and also improve semiconductors with outstanding separation of charge carriers (Wang et al., 2019). Among the different semiconductors, zirconia (ZrO₂) has been extensively used in numerous applications because of its remarkable physio-chemical properties, being a harmless element with good stability, cheap and eco-friendly material. But, due to its bandgap (~5 eV), visible region light-capturing capability is weak, the separation of photo-excited charge carrier's capability is low and quick recombination rate of photo-generated charge carriers weaken its usage as an effective solar photocatalyst material.

In order to overcome the above-mentioned problems and to improve its photocatalytic performance, doping with transition metal ions is an effective method. Furthermore, it is wellknown that structural defects show a significant role in physico-chemical properties. The addition of dopant ions can introduce structural defects, and change the oxygen vacancy into the host structure. In addition, the alteration of bandgap energy takes place to enhance its photocatalytic performance under visible light (Zhao et al., 2014, Poston et al., 2014, Agorku et al., 2015, Zhang et al., 2015). Furthermore, addition of dopant ions can facilitate adsorption of organic contaminants onto the surface of semiconductor, which is an improvement in the catalytic activity of host material. In addition, crystallite size, phase purity, dopant type and synthesis procedure can also influence photocatalytic performance of the oxides (Lopez et al., 2006, Zhao et al., 2015). Among the transition metal ions, copper (Cu) has been chosen as a dopant to over whelm the above-stated limits due to its better charge carriers separation efficiency. To the best of our understanding, a systematic study of Cu (0.1, 0.3, and 0.5 mol %)-doping ZrO₂ on photoelectrochemical (PEC) water oxidation performance and removal of organic dyes from wastewater has not been previously reported. Therefore, the present study focuses on the synthesis of highly efficient Cu-doped ZrO₂ catalysts following an inexpensive, eco-friendly and template-free hydrothermal method for solar PEC water oxidation and toxic dye degradation. Furthermore, the proposed work focuses on the dopant content influence on its optical properties.

Section snippets

ZrO₂ photocatalyst preparation

Pure ZrO₂ photocatalysts were synthesized according to a procedure previously reported (Venkata Reddy et al., 2020). In order to synthesize copper-doped ZrO₂ photocatalysts, 9 g of ZrCl₂·8H₂O and Cu (NO₃)₃.6H₂O (different molar ratios; 0.1, 0.3 and 0.5 mol%) were mixed with DI water and ammonia solution (100 ml) was added slowly under stirring. Then, the mixture was transferred to autoclave (200 mL), heated for 10 h at 230 °C and the obtained material was repeatedly cleaned, desiccated at

XRD analysis

Fig. 1(a) illustrates XRD patterns of the undoped and Cu-doped samples. As can be seen both tetragonal (JCPDS No.89-7710) and monoclinic (JCPDSNo. 65-1024) phases of ZrO₂ coexist in pure, 0.1 Cu–Zr and 0.3 Cu–Zr samples. The peaks observed at 30.26°, 34.95°, 50.41°, 59.83°, 62.96° and 74.31° are related to the (101), (110), (112), (211), (202) and (220) planes of tetragonal phase and the peaks observed at 24.1°, 28.1°, 38.8°, 45.1° and 55.4° are associated to monoclinic phase, and these peaks

Conclusions

In this investigation, Cu-doped ZrO₂ photocatalysts were prepared using the hydrothermal method and their PEC water oxidation and photocatalytic properties were studied. The optimal doped photocatalyst showed the superior photocatalytic activity over other samples under 100 min of visible light irradiation. The doped photoelectrodes exhibited greater photo-activity and improvement in both photocurrent densities and onset potential over the pure electrode. The XPS analysis revealed that dopant

CRediT authorship contribution statement

Ch Venkata Reddy: Writing - original draft, Writing - review & editing. I. Neelakanta Reddy: Writing - review & editing. K. Ravindranadh: Writing - review & editing. Kakarla Raghava Reddy: Writing - review & editing. Nagaraj P. Shetti: Writing - review & editing. D. Kim: Formal analysis, Writing - review & editing. J. Shim: Supervision, Writing - review & editing. Tejraj M. Aminabhavi: Supervision, Writing - review & editing.

Declaration of competing interest

The authors report no conflict of interest.

Acknowledgments

This work was supported by the National Research Foundation of Korea (NRF) and funded by the Ministry of Science of the Korean government (MEST) (NRF- 2017R1A4A1015581&-2019R1F1A1060655).

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Research articleCopper-doped ZrO2 nanoparticles as high-performance catalysts for efficient removal of toxic organic pollutants and stable solar water oxidation

Highlights

Abstract

Introduction

Section snippets

ZrO2 photocatalyst preparation

XRD analysis

Conclusions

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgments

Mol. Catal.

Compd

Chem. Eng. J.

Electrochim. Acta

J. Environ. Manag.

J. Environ. Manag.

J. Environ. Manag.

Mater. Des.

J. Solid State Chem.

Mater. Lett.

Enhanced visible light photocatalytic activity of multi-elements-doped ZrO2 for degradation of indigo carmine

J. Rare Earths

Formation of three-dimensional ordered hierarchically porous metal oxides via a hybridized epoxide assisted/colloidal crystal templating approach

ACS Appl. Mater. Interfaces

Synthesis, characterization and electrochemical properties of iron-zirconia solid solution nanoparticles prepared using a sol-gel technique

Phys. Chem. Chem. Phys.

Influence of oxygen atmosphere on the photoluminescence properties of sol–gel derived ZrO2 thin films

J. Sol. Gel Sci. Technol.

Synthesis, characterization, and photocatalytic activity of Y-doped CeO2 nanorods

ACS Catal.

Photocatalytic degradation of 2,4-dichlorophenoxiacetic acid and 2,4,6-trichlorophenol with ZrO2 and Mn/ZrO2 sol-gel materials

J. Sol. Gel Sci. Technol.

Preparation and physicochemical properties of ZrO2and Fe/ZrO2prepared by a Sol-Gel technique

Langmuir

Research article
Copper-doped ZrO₂ nanoparticles as high-performance catalysts for efficient removal of toxic organic pollutants and stable solar water oxidation

ZrO₂ photocatalyst preparation

Enhanced visible light photocatalytic activity of multi-elements-doped ZrO₂ for degradation of indigo carmine

Influence of oxygen atmosphere on the photoluminescence properties of sol–gel derived ZrO₂ thin films

Synthesis, characterization, and photocatalytic activity of Y-doped CeO₂ nanorods

Photocatalytic degradation of 2,4-dichlorophenoxiacetic acid and 2,4,6-trichlorophenol with ZrO₂ and Mn/ZrO₂ sol-gel materials