Dr Gurwinder Singh

Transition-metal nitrides have attracted significant attention because of their unique electronic and surface properties and superior chemical and mechanical stability. Although various metal nitrides nanostructures have been realized, it remains challenging to introduce porosity and the high specific surface in these nanostructures, but they are required to expand the application possibility of these materials in energy storage and conversion. Here, we report the preparation of nanoporous titanium carbonitride using a high-nitrogen-containing mesoporous carbon nitride, C3N6 (MCN-4), as a reactive template and titanium tetrachloride as the titanium source. Nitrogen adsorption and microscopic results reveal that the prepared samples are highly nanoporous in nature, and the optimized sample exhibits a specific surface area of 700 m2/g and a high specific pore volume of 1.3 cm3/g. With the slight variation of the amount of MCN-4 in the synthesis mixture, the composition and the crystal structure of the nanoporous titanium carbonitride can be finely controlled. Near-edge X-ray absorption fine structure and Raman spectroscopic analyses of these samples confirm that the titanium atoms are strongly bonded with both carbon and nitrogen. The electrochemical hydrogen evolution reaction measurements of the optimized nanoporous titanium carbonitride loaded with 5 wt % of platinum in acidic medium reveal a high electrocatalytic performance with the overpotential of 27 mV at the current density of 10 mA cm-2, which is similar to that of commercially available Pt/C which contains 20 wt % of Pt. The combination of nanoporous structure together with the highly conducting carbon matrix in these metal carbonitride samples really helps to enhance the electrocatalytic activity. This research reveals a great opportunity for the design of porous metal nitride-based nanostructures with different composition and the potential for these materials to be used in energy storage and conversion technologies.

We demonstrate a synthesis of copper nanoparticles decorated over nitrogen-doped mesoporous carbon with different N and Cu contents which exhibit conducting, redox, basic, adsorption, and excellent textural properties. These materials are prepared through a nanotemplating approach by simultaneously encapsulating sucrose, guanidine hydrochloride, and Cu(NO3)2 into the porous channels of mesoporous SBA-15 at a low carbonization temperature of 600 °C. The prepared materials exhibit an ordered mesoporous carbon framework with bimodal pores, decorated with nitrogen and Cu functionalities on the surface of the pores and in the wall structure. The presence of nitrogen functionalities in the porous carbon matrix not only helps to reduce the Cu ions but also stabilizes the nanoparticles and offers redox sites, which are beneficial for adsorption and electrochemical applications. The optimized sample exhibits the highest adsorption capacity of different gases such as CO2 ¿ 22.5 mmol/g at 273 K, H2 -13.5 mmol/g at 77 K at 30 bar and CH4 - 5 mmol/g at 298 K and 50 bar. We also demonstrate that the prepared material shows a high selectivity of adsorption towards CO2 in a mixture of CO2/H2 and CO2/CH4 and it also registers a high supercapacitance of 209 F g-1 at a current density of 1 A g-1 with excellent cyclic stability.

One of the key focuses of the agricultural industry for preventing the decline in crop yields due to pests is to develop effective, safe, green, and sustainable pesticide formulation. A key objective of industry is to deliver active ingredients (AIs) that have minimal off site migration and non-target activity. Nanoporous materials have received significant attention internationally for the efficient loading and controlled, targeted delivery of pesticides. This is largely made possible due to their textural features including high surface area, large pore-volume, and tunable pore size. Additionally, the easier manipulation of their surface chemistry and stability in different environments are added advantages. The unique features of these materials allow them to address the solubility of the active ingredients, their efficient loading onto the porous channels, and slow and controlled delivery over time. One of their major advantages is the wide range of materials that could be suitably designed via different approaches to either adsorb, encapsulate, or entrap the active ingredient. This review is a timely presentation of recent progress made in nanoporous materials and discusses critical aspects of pesticide formulation and delivery.

Reversible polymer electrolyte membrane (PEM) fuel cells have attracted significant research attention in the last decade due to the associated benefits. However, flow-field design of the bipolar end plates, among various other parameters, largely affects its performance. Thus, the present paper focuses on determining hydrogen storage capacity of a typical activated carbon (aC) electrode employed in a reversible modified PEM fuel cell with varied designs of flow-field. Three flow-field orientations - pin-type, parallel, and interdigitated - are used and their performance is evaluated. The fabrication method of the electrode, reversible modified PEM fuel cell, and different orientations of micro flow channels is disclosed. The characterization of the employed aC electrode is done using scanning electron microscopy (SEM), x-ray diffraction analysis (XRD), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). The fabricated cells are tested by linear voltage sweep and results are recorded. The result analysis revealed that the interdigitated flow-field design leads to better distribution of the reactants and encourages higher hydrogen adsorption in the carbon electrode compared to the other flow-field designs under consideration. The electrochemical hydrogen storage capacity of the carbon electrode with interdigitated flow-field design is found to be 1.47 weight percentage (wt. %), whereas for parallel and pin-type designs, it stands at 1.40 wt. % and 1.36 wt. %, respectively. The obtained energy storage density is comparable with the commercially available metal hydride based compressed hydrogen canisters. It is surely a step forward toward developing a reversible PEM fuel cell with enhanced performance capable of storing the charge, like a battery, with many potential applications.

In order to overcome the current energy and environment crisis caused by fossil fuels depletion and greenhouse gas emission, it is indispensable to introduce new, eco-friendly, high-performance materials into energy conversion and storage applications. 2D transition metal oxides (TMOs) are regarded as the promising candidates due to their excellent electrochemical properties. However, their innate poor electronic conductivity greatly restricts their applications in energy conversion and storage. This review discusses and summarizes the developed strategies to overcome the limitation through surface modification including defect engineering, heteroatom incorporation and interlayer doping, as well as hybridization with conductive materials. In addition, a detailed summary of their synthesis and applications in supercapacitors, lithium ion batteries and electrocatalysis is included. Finally, future prospective such as opportunities and challenges is discussed for the successful implementation of 2D TMOs in the field of energy applications.

Highly efficient, low-cost electrocatalysts having superior activity and stability are crucial for practical electrochemical water splitting, which involves hydrogen and oxygen evolution reactions (HER and OER). The sustainable production of hydrogen fuel from electrochemical water splitting requires the development of a highly efficient and stable electrocatalyst with low overpotential that drives electrochemical redox reactions. Electrochemical water splitting using highly active nickel-iron layered double hydroxide (NiFe LDH) catalyst having a very high turnover frequency and mass activity is considered as a potential contender in the area of electrocatalysis owing to the practical challenges including high efficiency and long durability at low overpotential, which shows great potential in future hydrogen economy. This review includes certain recommendations on enhancing the electrocatalytic performance of NiFe LDH-based electrocatalyst, particularly through morphology engineering, construction of hierarchical/core-shell nanostructures, and doping of heteroatoms through combined experimental assessment and theoretical investigations, which in turn improve the electrocatalytic performance. Finally, emphasis is made on the bifunctional activity of the NiFe LDH catalyst for overall water splitting. At the end, the conclusions and future outlook for the design of the NiFe LDH catalyst towards scale-up for their use as electrolyzer at the industrial level are also discussed.

Aqueous film-forming foam, used in firefighting, and biowastes, including biosolids, animal and poultry manures, and composts, provide a major source of poly- and perfluoroalkyl substances (PFAS) input to soil. Large amounts of biowastes are added to soil as a source of nutrients and carbon. They also are added as soil amendments to improve soil health and crop productivity. Plant uptake of PFAS through soil application of biowastes is a pathway for animal and human exposure to PFAS. The complexity of PFAS mixtures, and their chemical and thermal stability, make remediation of PFAS in both solid and aqueous matrices challenging. Remediation of PFAS in biowastes, as well as soils treated with these biowastes, can be achieved through preventing and decreasing the concentration of PFAS in biowaste sources (i.e., prevention through source control), mobilization of PFAS in contaminated soil and subsequent removal through leaching (i.e., soil washing) and plant uptake (i.e., phytoremediation), sorption of PFAS, thereby decreasing their mobility and bioavailability (i.e., immobilization), and complete removal through thermal and chemical oxidation (i.e., destruction). In this review, the distribution, bioavailability, and remediation of PFAS in soil receiving solid biowastes, which include biosolids, composts, and manure, are presented.

Slags are a co-product produced by the steel manufacturing industry and have mainly been utilised for aggregates in concreting and road construction. The increased utilisation of slag can increase economic growth and sustainability for future generations by creating a closed-loop system, circular economy within the metallurgical industries. Slags can be used as a soil amendment, and slag characteristics may reduce leachate potential of heavy metals, reduce greenhouse gas emissions, as well as contain essential nutrients required for agricultural use and environmental remediation. This review aims to examine various slag generation processes in steel plants, their physicochemical characteristics in relation to beneficial utilisation as a soil amendment, and environmental implications and risk assessment of their utilisation in agricultural soils. In relation to enhancing recycling of these resources, current and emerging techniques to separate iron and phosphorus slag compositions are also outlined in this review. Although there are no known immediate direct threats posed by slag on human health, the associated risks include potential heavy metal contamination, leachate contamination, and bioaccumulation of heavy metals in plants, thereby reaching the food chain. Further research in this area is required to assess the long-term effects of slag in agricultural soils on animal and human health.

In this investigation, a hybrid of metal sulfide and carbon nitride (CN) is synthesized by in-situ chemical conversion between metallic species and a single precursor of carbon, nitrogen and sulfur elements through a strong p-d conjugation approach. It is observed that the local chemical alteration in the vicinity of N atom in the CN template triggers the formation of a highly p-conjugated CN system and efficient p-d hybridization at heterointerface. This is accelerated by partial substitution of the Fe atom for Mn ions in the MnS phase which significantly enhances the battery performance, delivering 2031 mA h g-1 after 500 cycles with inverse capacity growth. Via systematic in-depth characterizations, it is found that the gradual increase of Li-ion diffusion coefficients and charge transfer kinetics for repeated cycling is ascribed to the highly dispersed and uniform particles that are confined within the CN template through a strong p-d hybridization.