Monodispersed core/shell nanospheres of ZnS/NiO with enhanced H2 generation and quantum efficiency at versatile photocatalytic conditions

Vempuluru Navakoteswara Rao; Parnapalle Ravi; Marappan Sathish; Nagappagari Lakshmana Reddy; Kiyoung Lee; Mohan Sakar; Pathi Prathap; Murikinati Mamatha Kumari; Kakarla Raghava Reddy; Mallikarjuna N Nadagouda; Tejraj M Aminabhavi; Muthukonda Venkatakrishnan Shankar

doi:10.1016/j.jhazmat.2021.125359

Monodispersed core/shell nanospheres of ZnS/NiO with enhanced H₂ generation and quantum efficiency at versatile photocatalytic conditions

J Hazard Mater. 2021 Jul 5:413:125359. doi: 10.1016/j.jhazmat.2021.125359. Epub 2021 Feb 9.

Affiliations

¹ Nanocatalysis and Solar Fuels Research Laboratory, Department of Materials Science & Nanotechnology, Yogi Vemana University, Kadapa 516005, Andhra Pradesh, India.
² Electrochemical Power Sources Division, Central Electrochemical Research Institute (CSIR-CECRI), Karaikudi 630003, Tamil Nadu, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
³ Department of Energy Chemical Engineering, School of Nano & Materials Science and Engineering, Kyungpook National University, 2559 Gyeongsang-daero, 37224 Sangju, Republic of Korea.
⁴ Department of Energy Chemical Engineering, School of Nano & Materials Science and Engineering, Kyungpook National University, 2559 Gyeongsang-daero, 37224 Sangju, Republic of Korea; Research Institute of Environmental Science & Technology, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu, South Korea.
⁵ Centre for Nano and Material Sciences, Jain University, Bangalore 562112, Karnataka, India.
⁶ Photovoltaic Metrology Laboratory, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012, India.
⁷ School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, NSW 2006, Australia.
⁸ Department of Mechanical and Materials Engineering, Wright State University, Dayton, OH 45324, USA.
⁹ Department of Pharmaceutics, SETs' College of Pharmacy, Dharwad 580007, Karnataka, India.
¹⁰ Nanocatalysis and Solar Fuels Research Laboratory, Department of Materials Science & Nanotechnology, Yogi Vemana University, Kadapa 516005, Andhra Pradesh, India. Electronic address: shankar@yogivemanauniversity.ac.in.

PMID: 33609871
DOI: 10.1016/j.jhazmat.2021.125359

Abstract

This investigation is first to elucidate the synthesis of mono-dispersed ZnS/NiO-core/shell nanostructures with a uniform thin layer of NiO-shell on the ZnS-nanospheres as a core under controlled thermal treatments. NiO-shell thickness varied to 8.2, 12.4, 18.2, and 24.2 nm, while the ZnS-core diameter remained stable about 96 ± 6 nm. The crystalline phase and core/shell structure of the materials were confirmed using XRD and HRTEM techniques, respectively. Optical properties through UV-vis spectroscopy analysis revealed the manifestation of red-shift in the absorption spectrum of core/shell materials, while the XPS analysis of elements elucidated their stable oxidation states in ZnS/NiO core/shell structure. The optimized ZnS/NiO-core/shell showed 1.42 times higher H₂ generation (162.1 mmol h^-1 g^-1_cat) than the pristine ZnS-core (113.2 mmol h^-1 g^-1_cat), and 64.5 times higher than the pristine NiO-shell (2.5 mmol h^-1 g^-1_cat). The quantum efficiency at wavelengths of 420, 365 nm, and 1.5 G air mass filters was found to be 13.5%, 25.0%, and 45.3%, respectively. Water splitting experiments was also performed without addition of any additives, which showed enhanced H₂ gas evolution of 1.6 mmol h^-1 g^-1_cat under the sunlight illumination. Photoelectrochemical measurements revealed the stable photocurrent density and minimized charge recombination in the system. The performed recyclability and reusability tests for five recycles demonstrated the excellent stability of the developed photocatalysts.

Keywords: Core-shell nanostructures; Hydrogen production; Photocatalysis; Quantum efficiency.