Development of cost effective and efficient electrocatalysts is crucial to generate H₂ as an alternative source of energy. However, expensive noble metal based electrocatalysts show best electrocatalytic performances which acts as main bottle-neck 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 m²/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/cm²) and HER (≈0.7 mA/cm²) 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.

The energy crisis, dependence on non-renewable energy resources and environmental pollution pose a great threat to the ecosystem. Consequently, the generation and utilization of hydrogen as a renewable, pollution-free, sustainable energy resource has attracted significant attention. In this case, different approaches have been explored, among which the electrochemical production of hydrogen through HER provides an efficient, green and clean approach for the mass production of H₂. Besides HER, other reactions, such as OER and ORR, are core reactions involved in different electrochemical devices that are being developed to produce green energy technologies. In all these reactions, the development of low-cost materials with high electrochemical activity compared to the state-of-the-art noble metal electrocatalysts is important. Over the last few decades, different catalyst materials have been developed for HER, OER and ORR. Among them, graphene-based materials have been widely explored either as a support material or active catalyst for the above-mentioned electrochemical reactions. Specifically, the intrinsic electrochemical activity of graphene (G) is negligible, and therefore, different strategies, including heteroatom doping, composite development and development of heterojunctions, have been used to improve its electrochemical characteristics for HER/OER and ORR. However, although great advancements have been made using N-doped graphene (NG)-based heterostructures and composites as active electrocatalysts, there is still a lack of understanding of their reaction mechanism and the active sites responsible for the enhanced electrochemical performances are still under debate. Hence, considering the research interest over the past few years on NG-based electrocatalysts, herein we attempt to present a holistic summary of the recent advances made in the synthesis strategies and understanding of the role played by the interface, composite development and active sites in HER/OER and ORR over NG-based electrocatalysts.

NaTaO₃ nanoparticles with a high surface area of 46.2 m²/g have been successfully synthesized using a polymeric citrate precursor route. As-prepared nanoparticles were extensively characterized by X-ray diffraction, Fourier transform infrared, transmission emission microscopy, and scanning electron microscopy studies for the analysis of phase purity, crystallinity, and morphology. NaTaO₃ nanoparticles show efficient photo-induced removal of the methylene blue dye under sunlight, which were confirmed by using liquid chromatography–mass spectroscopy. 86% dye has been degraded in 200 min at neutral pH, whereas the same amount of dye was decolorized in only 80 min at alkaline pH. Also, the dielectric behavior of the as-prepared nanoparticles at different annealing temperatures was explained by the Maxwell–Wagner polarization mechanism. At 500, 600, and 700 °C annealing temperatures, the dielectric constant and dielectric loss at 500 kHz for the samples were found to be 21.5, 18, and 16 and 0.012, 0.022, and 0.029, respectively. The unsaturated hysteresis loop shows weak ferroelectric behavior of NaTaO₃ nanoparticles with remanent and saturation polarizations of 0.0013 and 0.21 μC/cm², respectively, and S-E hysteresis shows a bipolar strain of 0.10%.