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V Navakoteswara Rao, Speaker at Catalysis Conferences
National Nanofab Center, Korea, Republic of
Title : Monodispersed core/shell nanospheres of ZnS/NiO with enhanced H2 generation and quantum efficiency at versatile photocatalytic conditions


Hydrogen gas is a cleaner fuel and generates electrical energy in proton exchange membrane fuel cells with high efficiency and the best alternative energy for alternative 1. The present investigation is the 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 was varied to be 8.2, 12.4, 18.2, and 24.2 nm, while the ZnS-core diameter was fixed as 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 optical properties 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 showed1.42 times higher H2 generation (162.1 mmol.h-1.g-1cat) than the pristine ZnS-core (113.2 mmol.h-1.g-1cat) and 64.5 times higher than the pristine NiO-shell (2.5 mmol.h-1.g-1cat) owning to the many reasons (a) uniform core-shell structure (b) monodispersed nanospheres, (c) high surface area and more number of active sites and (d) Vacant 3d orbital. 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 was also performed without adding any additives, which resulted in an enhanced H2 gas evolution of 1.6 mmol.h-1.g-1cat under sunlight illumination. Photo-electrochemical measurements revealed a stable current 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. Based on the characterization properties we proposed the plausible photocatalytic water splitting mechanism for superior photocatalytic hydrogen generation under solar light irradiation as shown in Figure, here majorly three steps occur i.e, (i) photon energy absorption (ii) charge carrier migration, and (iii) redox reaction NiO shell thickness protects from the photo-corrosion and charge carrier recombination, finally give good yield hydrogen fuel conversion efficiency.

Keywords: Hetero junction, Nanohybrid, photocatalyst, Wurtzite, and cubic.


Dr. V. Navakoteswara Rao was awarded a Bachelor of Science (Maths, Physics, and Chemistry) in April 2011 from Sri Venkateshwara Arts College, Tirupati affiliated with Sri Venkateshwara University, Tirupati. He has obtained a Master of Science in the Department of Chemistry in April 2014 from Sri Venkateshwara University, Tirupati. Further, He has received a Bachelor of Education in Physical Science and Mathematics Methodology in November 2015 from Sri Krishna Devaraya University. He qualified Council of Scientific Industrial Research (CSIR-UGCNET) All India Rank 43rd rank in chemical sciences 2014 and Graduate Aptitude Test in Engineering (GATE-2018) with a GATE score is 340. He was selected and MNRE: YVU-CECRI Project worked as a Junior Research Fellow as well as enrolled Ph.D. on “Hierarchical Composite Nanostructure Photocatalyst For Water Splitting Under Solar Light Irradiation” under the supervision of Prof. M.V. Shankar in Nanocatalysis and Solar Fuels Research laboratory during March 2016 to April 2018 as a Junior Research Fellow. Later he was upgraded from Junior Research Fellow to Senior Research Fellow (May 2018 to March 2019). To continue doctoral research V. Navakoteswara Rao was awarded Senior Research Fellowship by the Council of Scientific Industrial Research (CSIR-SRF) Pusa; New Delhi, India. In order to, he has selected prestigious followership which is the Brain pool program-2021 working as a senior scientist at the Korea Advanced Institute of Science & Technology (KAIST), Daejeon, Republic of Korea.  He has authored 40 publications, 1 book (Monograph), 2 book chapters, and presented papers in 27 international and national conferences he won two best poster presentation awards in National/International conferences and a cumulative Impact factor is 315.5 with H-Index 19, I-10 Index-25, and Cite score is 1255 (Various journals Had been cited).