Electrocatalytic and Enhanced Photocatalytic Applications of Sodium Niobate Nanoparticles Developed by Citrate Precursor Route (original) (raw)

Development of cost effective and efficient electrocatalysts is crucial to generate H 2 as an alternative source of energy. However, expensive noble metal based electrocatalysts show best electrocatalytic performances which acts as main bottleneck for commercial application. Therefore, non-precious electrocatalysts have become important for hydrogen and oxygen evolution reactions. Herein, we report the synthesis of high surface area (35 m 2 /g) sodium niobate nanoparticles by citrate precursor method. These nanoparticles were characterized by different techniques like X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Electrocatalytic properties of cost-effective sodium niobate nanoparticles were investigated for HER and OER in 0.5 M KOH electrolyte using Ag/AgCl as reference electrode. The sodium niobate electrode showed significant current density for both oeR (≈2.7 mA/cm 2) and HER (≈0.7 mA/cm 2) with onset potential of 0.9 V for OER and 0.6 V for HER. As-prepared sodium niobate nanoparticles show enhanced photocatalytic property (86% removal) towards the degradation of rose Bengal dye. Dielectric behaviour at different sintering temperatures was explained by Koop's theory and Maxwell-Wagner mechanism. The dielectric constants of 41 and 38.5 and the dielectric losses of 0.04 and 0.025 were observed for the samples sintered at 500 °C and 700 °C, respectively at 500 kHz. Conductivity of the samples was understood by using power law fit. With every passing day, demand for global energy is growing exponentially, which has sparked intense research to develop sustainable, efficient energy resources and better storage mechanisms. Recently researchers have focussed on to develop materials having diverse applications. So as a consequence, there is great surge in development of active materials for energy generation purposes and storage applications. In view of the energy generation, hydrogen is considered as an alternative energy source for next generations which could replace conventional fossil energy sources 1,2. While as for energy storage and energy transfer processes, materials with high and stable value of dielectric constant and low dielectric loss are gaining interest 3. For energy generation, splitting of water through the processes like photocatalysis and electrocatalysis is considered as promising, non-toxic and environment friendly way for production of hydrogen 4-7. During electrocatalytic water splitting, hydrogen (H 2) is produced through hydrogen evolution half-cell reaction (HER) and oxygen (O 2) is evolved via oxygen evolution half-cell reaction (OER). However, the state-of-art platinum-based materials for HER and noble metal electrocatalysts like IrO 2 and RuO 2 for OER acts as bottleneck for large scale commercial application because of their scarcity and precious nature. Another important reason that hinders the practical application of electrocatalysis is that the OER needs large over potential due to complex four step proton coupled electron reaction mechanism. Even after the use of active catalysts like IrO 2 and RuO 2 , OER shows sluggish kinetics 8-10. In comparison to OER, HER is only two electron transfer process hence requires low energy (over potential) to overcome the kinetic barrier. To date, IrO 2 and RuO 2 are considered as most appropriate electro OER catalysts due to their low over potential,