Morphology controlled synthesis of 2D heterostructure Ag/WO3 nanocomposites for enhanced photoelectrochemical CO2 reduction performance

doi:10.1016/j.jcou.2020.101284

Journal of CO2 Utilization

Volume 41, October 2020, 101284

https://doi.org/10.1016/j.jcou.2020.101284 Get rights and content

Highlights

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In-situ hydrothermal synthesis of silver supported tungstate oxide.
•
Highly dispersed 2−10 nm Ag nanoparticles over the tungsten oxide nanorod.
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Efficient CO₂RR with high current density of 0.4 mA cm⁻².
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Selective product formation of formic acid.

Abstract

Supporting nanomaterials having strong metal-support interaction is the key to an efficient catalyst. The present paper describes a morphology-controlled synthesis of silver (Ag) nanoparticles supported on nanostructured tungsten oxide (WO₃) for selective photoelectrocatalytic carbon dioxide reduction reactions (CO₂RR) under visible light irradiation. Highly dispersed Ag on WO₃ nanorod was synthesized by a one-pot preparation method in the presence of cetyltrimethylammonium bromide (CTAB). The synthesis strategy remained intact and reproduced by varying loading of Ag, which was further confirmed by various characterization techniques like XRD, SEM, TEM, STEM elemental mapping, Raman, XPS, FT-IR, and BET analysis. The morphological growth of the WO₃ nanorod (NR) and the related mechanism was studied and discussed in the paper. 1.5 wt % Ag showed optimum loading for high dispersion over WO₃-NR and efficient CO₂RR with high current density (0.4 mA cm⁻²), towards the desired selective product formation (formic acid). The efficiency of the catalyst was further correlated with cluster vacancies on the interface of Ag particle and WO₃ nanorod by positron doppler broadening (DB) spectroscopy.

Graphical abstract

Introduction

The demand for advanced energy materials towards generating clean energy fuels from the rising global carbon dioxide (CO₂) has attracted enormous attention in recent decades [1,2]. Among the various known approaches, adequate photo-/electrochemical (PEC) conversion of CO₂ to fuels has become inevitable and addresses the CO₂ recycling with obtained solar fuels [3]. From the last few years, owing to the design & development of new energy materials, many researchers have devoted their efforts to synthesize nanostructures with increased charge transfer activity for high PEC performance [4,5]. Consequently, the numerous n-type semiconductor materials, including TiO₂ [6], ZnO [7], BiVO₄ [8], TiNT [9] and WO₃ [[10], [11], [12]] have been explored widely for solar energy conversions, mainly because of their high chemical stability, environmental benign nature, and reasonable abundance. In addition, WO₃ is well reported for favorable band edges (having high work function) with excellent optical/conductive properties for PEC water oxidation reactions [8]. However, these semiconductor materials have certain limitations, such as broad light absorption due to the large band gap (>2.6 eV), higher electron-hole recombination rate that limits their photoconversion efficiency [13,14].

In general, the functional properties of materials are dimensionally dependent, and their nanoscale heterostructures can enhance the optical, electronic, and morphological properties. Recently, the morphology-controlled synthesis of semiconductors and their modification with noble metals has acquired great research interests in photo-/electrocatalysis to resolve the above issues. Thus, rational design and synthesis of semiconductor nanostructures with well-controlled sizes and shapes are crucial tasks for their desired application [13,15,16]. Because of high intrinsic doping density and extensive potential applications of nanostructured WO₃ semiconductors proves to be interesting ultrafast kinetics enhance the electron/hole pair separation [14,17].

Many recent efforts have focused on two-dimensional (e.g., nanorods and nanowires) synthesis of nanomaterials due to their very high accessible surface to volume ratio and easily accessible of active sites [18,19]. A simple preparation method, which governs the nucleation and kinetics growth of the nanoparticles, is of paramount importance. Bimetallic nanoparticles are considered as emerging materials due to their potential activity and synergetic properties or capabilities of two metals as compared to the monometallic ones [20]. The catalytic efficiency of nanostructures is primarily governed by the size and shape of the nanocrystals and the composition of the metals as well as to the support used [21]. Nobel metal supported on various transitional and non-transitional metal oxide nanoparticles has been of interest owing to their very interesting size-dependent properties in various reactions [22]. Much research efforts have been made for the synthesis of uniformly dispersed Ag nanoparticles over WO₃-NR supports due to their excellent synergistic effect [23]. However, it remains a challenge among researchers to develop well-defined nanoarchitecture compositions [24,25].

In the view of above context, we examined the growth of morphology-controlled synthesis of 2D heterostructures (WO₃/Ag) nanocomposites for enhanced PEC CO₂ reduction reaction (CO₂RR). However, The positron doppler broadening (DB) spectroscopy is being used to investigate the interface defect (WO₃/Ag) related efficiency and the uniformity of the catalyst.

Section snippets

Synthesis growth of Ag/WO₃-NR

The morphology-controlled synthesis and growth of Ag supported on WO₃ nanorod can be explained from Scheme 1. Herein, in the absence of silver ions, formation of the WO₃ nanorod was not observed. Whereas the presence of Ag⁺ ions directs the growth of nanorod in one direction by adhesion of atoms, ions, or molecules into certain crystal planes of tungsten, and it is prominent, which favors the growth of WO₃-NR. However the nanorod formation mechanism is not so precise [25]. However, as

Synthesis of WO₃/Ag heterostructures

Highly dispersed Ag supported on WO₃ nanorod with different loading of silver was synthesized by the modified reported method [24,34]. In a typical synthesis process, we used tungstic acid (H₂WO₄) and silver nitrate (AgNO₃) a precursor salt in the presence of cetyltrimethylammonium bromide (CTAB) as a surfactant. An aqueous solution of AgNO₃ was added to partially soluble H₂WO₄ in a two necked round bottom flask under vigorous stirring at 50 °C. Subsequently, CTAB was added to the reaction

Conclusion

In this report, we have illustrated the facile synthesis of Ag/WO₃-NR with their mechanism for the morphology-controlled growth of WO₃-NR. The synthesized Ag/WO₃-NR was used further for photoelectrocatalytic CO₂RR, where it exhibits the excellent selectivity for the conversion CO₂ into formate. Consequently, the 1.5 wt % Ag/WO₃ catalyst is the optimized loading amount of Ag for CO₂RR, which is also prudent by surface morphological characterizations, and positron doppler broadening spectra

CRediT authorship contribution statement

Bappi Paul: Conceptualization, Methodology, Validation, Investigation, Writing - original draft, Funding acquisition, Funding acquisition. Nilesh Manwar: Conceptualization, Methodology, Validation, Investigation, Writing - original draft, Funding acquisition. Piyali Bhanja: Writing - original draft, Methodology, Validation, Investigation. S. Sellaiyan: Conceptualization, Methodology, Validation, Investigation, Writing - original draft. Sachin K. Sharma: Methodology, Validation, Investigation.

Declaration of Competing Interest

Authors have no conflicts to declare.

Acknowledgments

B.P thanks SERB-DST New Delhi, India for financial support in the form of National Post-Doctoral fellowship of Project (PDF/2016/001948) and NM thankful to CSIR-HRDG, New Delhi for CSIR-Nehru Science Postdoctoral Research Fellowship.

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¹: Authors contributed equally.

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Morphology controlled synthesis of 2D heterostructure Ag/WO3 nanocomposites for enhanced photoelectrochemical CO2 reduction performance

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Synthesis growth of Ag/WO3-NR

Synthesis of WO3/Ag heterostructures

Conclusion

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgments

Catalysis research of relevance to carbon management: progress, challenges, and opportunities

Chem. Rev.

Transformation of carbon dioxide

Chem. Rev.

Solar carbon fuel via photoelectrochemistry

Catal. Today

Emerging renewable and sustainable energy technologies: state of the art

Renew. Sustain. Energy Rev.

A place in the sun for Arti fi cial photosynthesis?

ACS Energy Lett.

Noble metal–metal oxide nanohybrids with tailored nanostructures for efficient solar energy conversion, photocatalysis and environmental remediation

Energy Environ. Sci.

Two-dimensional ZnO for the selective photoreduction of CO2

J. Mater. Chem. A.

WO 3 mesocrystal-assisted photoelectrochemical activity of BiVO 4

NPG Asia Mater.

Photoelectrochemical reduction of CO2 with TiNT

Mater. Sci. Semicond. Process.

Controlled synthesis of novel Z-scheme iron phthalocyanine/porous WO3 nanocomposites as efficient photocatalysts for CO2 reduction

Appl. Catal. B Environ.

Photoelectrocatalytic reduction of CO2 into formic acid using WO3–x/TiO2 film as novel photoanode

Trans. Nonferrous Met. Soc. China.

Photocatalytic reduction of CO2 over a hybrid photocatalyst composed of WO3 and graphitic carbon nitride (g-C3N4) under visible light

J. CO2 Util.

Charge separation, band-bending and recombination in WO3 photoanodes

J. Phys. Chem. Lett.

Two-dimensional amorphous heterostructures of Ag/a-WO 3-x for high-efficiency photocatalytic performance

Appl. Catal. B Environ.

Shape-controlled nanoparticles as anodic catalysts in low temperature fuel cells

ACS Energy Lett.

Phase stability diagrams of group 6 magnéli oxides and their implications for photon-assisted applications

Chem. Mater.

Heterostructure Ag@WO3–x composites with high selectivity for breaking azo-bond

Chem. Res. Chinese Univ.

Morphology controlled synthesis of 2D heterostructure Ag/WO₃ nanocomposites for enhanced photoelectrochemical CO₂ reduction performance

Synthesis growth of Ag/WO₃-NR

Synthesis of WO₃/Ag heterostructures