Navneet Kumar Gupta’s research while affiliated with Indian Institute of Science Bangalore and other places

Artificial photosynthesis, which mimics the natural process used by plants, offers a promising strategy for harnessing solar energy to produce valuable fuels. One intriguing approach is the photocatalyst-enzyme attached system, where a photocatalyst captures light energy and transfers it to an enzyme to drive specific chemical reactions. This study describes the synthesis of a novel photocatalyst (MWCNTCEBr) formed by coupling multiwall carbon nanotubes (MWCNTs) with a dye ethidium bromide (EBr) via a condensation reaction. The resulting photocatalyst exhibits excellent charge separation and migration abilities, leading to enhanced photocatalytic activity. Notably, MWCNTCEBr photocatalyst successfully converts α-Ketoglutarate to L-Glutamate (81.9%) and photo-regeneration of NADH (76.20%) under the influence of solar radiation. Therefore, the study demonstrates the development and the application of MWCNTCEBr photocatalyst for impressive NADH regeneration and bio-transformation.

Utilizing a catalytic approach for producing biodiesel from non‐edible oils holds promise as a solution for the next generation of fuels. Therefore, the emerging research on replacing conventional catalysts and developing new waste‐derived heterogeneous catalysts with acid–base properties in the intensified biodiesel production process aims to achieve significant scientific outcomes including developing a low‐cost biorefinery and mitigating the increasing energy demand. Hence, a prospective replacement of green renewable solid acid catalysts over conventional or regularly used catalysts in the production of biodiesel using hydrodynamic cavitation‐assisted reactors has been discussed in this review. The synthesis and importance of different solid acid catalysts zeolite‐based and heteropolyacids is also discussed in this review. It is concluded that, to date, these catalysts are well used in biomass pyrolysis and very minimal in the pretreatment of lignocellulosic biomass, but there is no proper report on their application in the biodiesel synthesis from various non‐commercial feedstocks. In this study, it is also reported that the hydrodynamic cavitation‐assisted synthesis of biodiesel represents a novel approach with the potential to significantly boost yield and serve as a breakthrough method for industrial applications. The economic survey, circular economy, and life‐cycle assessment studies concerning the proposed study are also presented in this study, from which it is concluded that the complete replacement of these green catalysts in the production of biodiesel will aid in the development of a clean and green sustainable environment.

Due to its layered structure and appropriate electronic configuration, two-dimensional MoS2 has been considered a reliable and inexpensive electrocatalyst and electrode material for the oxygen reduction reaction (ORR). Additionally, the MoS2 and reduced graphene oxide (rGO) structure can act as a good host for other nano-catalysts. However, the catalytic activity of pristine MoS2 is not as effective as the industrial targeted values. In this work, nickel-MoS2 (Ni/MoS2) and Ni/MoS2-rGO composites are synthesized and evaluated as catalysts for ORR at the cathode. Electrochemical studies using a rotating disk electrode system confirmed that the as-synthesized catalyst exhibits good electrocatalytic activity to ORR in alkaline media (0.1 M KOH) and followed the desirable 4-electron transfer process. Ni/MoS2-rGO composite displays a current density of − 11.1 mA/cm² and half-wave and onset potentials of 0.74 V and 0.87 V, respectively, at 2400 rpm, whereas the bare MoS2 shows the values of limiting current density, half-wave potential, and onset potential of − 5.8 mA/cm², 0.61 V, and 0.79 V, respectively. Numerous highly active Mo sites, high conductivity, and high specific surface area in MoS2-rGO make it a novel catalyst material for ORR. Ni further enhances conductivity and is involved in electrochemical reactions. The onset potential slightly shifts towards the lower value after the potential cycling, whereas the limiting current density decreases by ≈9.0% for Ni/MoS2-rGO, which shows its good stability in alkaline media. Therefore, Ni/MoS2-rGO composite can be a good candidate for electrode catalyst material for alkaline fuel cells. Graphical Abstract

The circular economy and the depletion of Earth's resources highlight the need to transform waste into value‐added emerging materials like carbon quantum dots (CQDs), which show great promise in energy storage, catalysis, and other applications. The production of catalytically active CQDs from biomass garners significant attention due to their unique advantages, such as ease of availability, natural abundance, renewability, low cost, and environmental friendliness. This review addresses the synthesis of CQDs from biomass, the factors influencing their properties and performance, and their diverse applications in catalytic hydrogenation reactions, selective reduction of nitroaromatic compounds, and azo dyes. Recent studies demonstrate that biomass‐derived CQDs exhibit significantly improved catalytic activity, selectivity, and stability, effectively addressing the long‐standing challenges of low activity and poor stability in catalysts derived from conventional sources.

The sustainable development of energy has always been a concern. Upgrading biomass catalysis into hydrocarbon liquid fuels is one of the effective methods. In order to upgrade biomass derivative guaiacol by Hydrodeoxygenation (HDO) catalysis, this article report a three‐dimensional honeycomb structure biochar loaded with Ni nanoparticles and phosphomolybdic acid demonstrating excellent catalytic performance in a short period of time. This is due to the porous structure of biochar, which allows Ni metal nanoparticles to be highly uniformly dispersed on the support, which enhances the catalytic hydrogenation of guaiacol in terms of both rate and efficiency. Furthermore, it was observed that the added phosphomolybdic acid dissolved within the temperature range of 78–90 °C, functioning as a homogeneous catalyst in the process. This proves advantageous, as the phosphomolybdic acid becomes accessible at any location within the porous Ni/C catalyst. The detailed characterization data revealed that the carbon support prepared in this study has a high specific surface area of up to 1375.61 m²/g. Additionally, the phosphomolybdic acid exhibited rich acidity, with Brønsted and Lewis acid contents of 2.55 μmol/g and 21.45 μmol/g, respectively. Reaction data demonstrated that at 240 °C for 180 min, 100 % conversion and 97.9 % cyclohexane selectivity were achieved. This study introduces a bifunctional catalyst with an unique catalyst's structure, facilitating a heterogeneous‐homogeneous catalytic reaction and delivering an efficient catalytic effect.