Electrochemical CO₂ reduction (CO₂R) to chemicals and fuels has made tremendous progress since the introduction of gas diffusion electrodes (GDEs) to overcome mass-transfer limitations and enable industrial-scale current densities. The advancement in the field, however, has come with new challenges that are related to the stability and degradation of the GDE due to flooding issues, which currently hinder the scale-up. Here, we investigated the effect of six different binding materials (Nafion, polytetrafluoroethylene, Fumion, Pention, poly(vinyl alcohol), and polypyrrole) on the stability and performance of Ag-based GDEs for CO₂R to CO in alkaline media. All binders show a decrease in the Faraday efficiency (FE) of CO and increase in hydrogen evolution reaction over time. The most hydrophilic GDE based on polypyrrole can uphold a higher FE of CO for longer times, which is contrary to a common belief that low wettability is required for long-term stability. By using a range of tools (SEM-EDX, SEM-FIB, X-ray diffraction, and contact angle measurements) for the postelectrolysis characterization of the GDEs, we show that the performance loss is related to flooding, bi(carbonate) precipitation, and catalyst agglomeration. These results contribute to a better understanding of the stability issues in GDE-based CO₂ electrolyzers.

There is no denying that the world is heading towards an era powered by green energy resources. The need for highly efficient devices for sustainable energy storage and utilization is vital in transitioning towards the full-time realization of renewable energy for our society. In the last four decades, there have been groundbreaking developments in the large-scale commercialization of Li-ion batteries, electric vehicles, and solar power, all made possible by an in-depth understanding of the science of materials. Theoretically, there exists no problem in the production of green hydrogen, as oxides of Ir, Rh, and Pt, and the elements themselves, are excellent catalysts for the electrochemical hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) with fast kinetics. Thus, more work remains to be done in the area of green energy material technology. The problem lies with the critical availability and cost of these materials, which is the underlying motivation for finding alternative energy materials and technologies. This energy transition era presents us with an opportunity to expand our horizons and knowledge in chemical engineering, materials science, and allied fields through two-dimensional (2D) nanomaterials. These materials exhibit intriguing characteristics in contrast to their bulk counterparts, coupled with interchangeable electronic properties depending on the synthesis methodologies employed. The chapter begins by introducing the family of graphene nanosheets and expands into a discussion of advanced 2D families, such as transition metal dichalcogenides (TMDs), MXenes, transition metal oxides (TMOs), and hexagonal boron nitride (h-BN).

The pursuit of scalable and efficient electrode materials is essential for advancing lithium-ion battery (LIB) technologies. Among the anode candidates, spinel-structured ZnMn2O4 (ZMO) is attractive due to its high theoretical capacity (∼1008 mAhg−1), environmental friendliness, and cost-effectiveness. However, large volume expansion during lithium insertion/extraction and poor electrical conductivity limit its long-term performance. Conventional ZMO nanostructure synthesis involves complex, multi-step processes requiring high-temperature calcination, making them time-consuming and unsuitable for large-scale production. To overcome these challenges, we developed a rapid, one-pot microwave-assisted hydrothermal synthesis technique to fabricate a ZnMn2O4/α-MnO2 (ZMO/α-MO) nanocomposite. This method reduces processing time and enables in-situ formation of a mixed morphology. The composite consists of nano-polyhedral ZnMn2O4 integrated with 1D α-MnO2 nanowires, which buffer volume changes and enhance structural stability during cycling. The synergistic architecture improves electron transport, reduces lithium-ion diffusion paths, and provides superior mechanical resilience. Electrochemical results showed that the ZMO/α-MO nanocomposite as an anode material in the Li half-cell delivered a high discharge capacity of 891.6 mAhg−1 at 100 mAg−1 after 100 cycles. The electrode exhibited stable cycling across varying current densities and self-adaptive capacity recovery at different rates. These performance enhancements are attributed to improved reaction kinetics enabled by its porous structure, high surface area, and controlled volume expansion of ZMO nanoparticles composited with α-MnO2 nanowires. This green, scalable, and time-saving synthesis strategy offers promising potential for next-generation high-performance LIBs.

The development of advanced catalysts with innovative nanoarchitectures is critical for addressing energy and environmental challenges such as the electrochemical CO₂ reduction reaction (CO₂ RR). Herein, the synthesis of an innovative copper–sulfur planar structure, Cu–S–BDC, within a metal–organic framework (MOF) catalyst is presented, which demonstrates 100% selectivity toward formate as the sole carbon product. Structural analysis and surface characterizations reveal that Cu–S–BDC exhibits quasi-2D inorganic building units, with Cu bonded to two S-CH (Formula presented.) groups and one BDC linker, while carboxylate groups adopt a bridging coordination mode. This unique arrangement not only imparts remarkable structural stability but also enhances the electronic properties of the MOF, as evidenced by a narrow bandgap of 1.203 eV that facilitates efficient charge transfer and increased electrochemical current density in CO (Formula presented.) RR. Notably, it offers a Faradaic efficiency of 92% for formate at an overpotential as low as −0.4 V versus the reversible hydrogen electrode (RHE) in an aqueous electrolyte of 1 m KOH, as well as a current density of −25.8 mA cm² at −0.9 V versus RHE, averaged over 24 h of electrolysis. This study highlights a fresh perspective in the field of MOF electrocatalysts by demonstrating that engineering the metal coordination environment can significantly enhance the electronic properties and consequently improve the electrocatalytic performance of these materials.

This research presents a novel investigation into the intricate relationship between temperature and the performance of polymeric triboelectric nanogenerators experimentally and theoretically. A comprehensive investigation has been conducted to delve into the underlying mechanisms governing the temperature dependence of a triboelectric nanogenerator. The study centers on a meticulously fabricated triboelectric nanogenerator using a polyimide (PI) nanofiber membrane and encompasses a broad temperature spectrum, analyzing behavior at both room temperature and elevated temperatures. The developed PI nanofiber membrane functions as a versatile platform for converting mechanical energy into electrical with potential to harvest energy even from ultra-low frequency movements like the human pulse or the act of scratching. Additionally, the material boasts a sophisticated triboelectric response strategy. This means it exhibits its peak performance within a specific temperature range, optimizing energy conversion efficiency under these conditions. Open circuit voltage (VOC) reaches 11.76 V at 160 °C, an 84.4 % improvement compared to room temperature. A Kelvin probe force microscopy (KPFM) and fast Fourier transform (FFT) analyses have been performed for the first time to decouple the energy conversion mechanism, confirming its primary dependence on triboelectricity. A comprehensive theoretical study explores the working mechanisms of contact electrification (CE) and the triboelectric effect (TE) during temperature elevation in these nanogenerators (TENGs). This work highlights the potential of PI nanofibers as high-performance, flexible nanogenerators, particularly for applications requiring operation in smart, high-temperature environments. The emphasis on decoupling the mechanism through novel techniques and a theoretical framework on the temperature dependence strengthens the originality and contribution of the study.

Nickel coatings are widely used for corrosion and wear resistance, often undergoing post-treatment to enhance performance. Depending on their final application, Ni-coated steel may be subjected to mechanical forming processes to produce cylindrical can shapes, commonly used as battery cases or food storage containers where corrosion resistance is critical. Before mechanical forming, a key thermomechanical process called temper rolling is applied to improve coating adhesion, reduce residual stress, and minimize surface defects. This study systematically investigates the corrosion mechanisms of Ni-electroplated steel after annealing and temper rolling, demonstrating that both processes enhance localized corrosion resistance by modifying microstructure, surface morphology, and surface oxide evolution. These treatments promote passivity by increasing NiO content relative to Ni(OH)₂, significantly improving charge transfer resistance. Additionally, iron diffusion from the steel substrate generates an electrical surface potential gradient within the coating, affecting nobility variations across different regions. Post-corrosion analysis of temper-rolled samples reveals that corrosion initiation occurs at submicron grains, where structural gaps facilitate substrate exposure, underscoring the role of processing routes in enhancing coating durability.

Optimizing the deposition parameters in the fabrication of passivating contacts for crystalline silicon solar cells is critical for improving efficiency. This study explored the influence of varying RF power of Plasma-Enhanced Chemical Vapor Deposition (PECVD) on the quality of hydrogenated intrinsic amorphous silicon ( a-Si:H) films. The aim is to manufacture in-situ phosphorous-doped poly-Si/SiO_x/c-Si passivating contacts with a-Si:H as buffer layer between the tunnelling oxide and the n-type poly-Si. The microstructure factor of our intrinsic layers increases from 0.176 to 0.804, that is from higher to lower film density, as the RF power increases from 5 W to 55 W. Analysis using X-ray Photoelectron Spectroscopy and Optical Microscopy indicates that the Si content in SiO_x is correlated with the formation of pinholes. Our detailed analysis showed that varying the RF power when depositing a-Si:H contacting layer is crucial in altering both the Si⁴⁺ content in SiO_x and the pinhole density, due to the interplay between the plasma etching and the buffering effects during of the a-Si:H layer growth. Notably, the sample processed with 25 W exhibited the maximum pinhole density, the lowest Si⁴⁺ content in SiO_x and the deepest phosphorus in-diffusion, potentially yielding superior results in passivation quality and contact resistivity under optimized PECVD conditions.

Titanium dioxide (TiO₂) has been widely used as a photocatalyst in CO₂ reduction reaction (CO₂RR) due to its low cost, high stability, and strong absorption in the close-to-visible ultra-violet (UV) range. However, TiO₂ films suffer from poor selectivity in CO₂ reduction due to their unfavorable electronic properties. In this work, we address this challenge by fabricating ultra-thin (14 nm) defective TiO₂ films (TiO₂-DTF) to enhance the selectivity of CO₂RR towards formate. TiO₂ sol was prepared using a facile and reproducible sol-gel method and directly deposited onto the surface of the electrode, forming a uniform, ultra-thin TiO₂ layers with a high number of defects. The activity of the TiO₂-DTF catalyst was studied in both photochemical and photoelectrochemical CO₂RR, indicating that the applied potential increases both the yield and selectivity of CO₂RR to formate. The TiO₂-DTF photocathode exhibited remarkable formate production during CO₂ reduction, achieving exceptional Faradaic efficiencies of up to 45 %. To elucidate the mechanism of photoelectrochemical CO₂RR on TiO₂-DTF, an in-situ attenuated total reflection Fourier-transform infrared spectroscopy (in-situ ATR-FTIR) was used and experimental results were supported by density functional theory (DFT) calculations. This study demonstrates that ultra-thin highly defective TiO₂ film, prepared using the cost-effective and environmentally friendly sol-gel method, can be used as photoelectrocatalyst for CO₂ reduction.

In the search for effective high-tech materials for energy conversion and storage devices, spinel-structured nickel ferrite (NiFe₂O₄) has been identified as a promising anode material for lithium-ion batteries (LIBs). However, the influence of different morphologies and surface properties of NiFe₂O₄ nanoparticles on battery performance is hardly addressed. To understand the effect of different morphologies and surface properties on the lithium-ion storage performance, NiFe₂O₄ nanoparticles were synthesized through four different synthesis conditions: NFO-S, NFO-U, NFO-G, and NFO-C. The formation of polycrystalline inverse spinel NiFe₂O₄ was confirmed through XRD, FTIR, and Raman spectroscopy. The morphologies of the obtained samples were studied using FESEM, and it was found that the four different synthesis conditions employed here enabled us to obtain NiFe₂O₄ with four different morphologies. The surface chemistry, surface area and porosity of the NiFe₂O₄ samples were respectively characterized using XPS and BET. The electrochemical performance of the four NiFe₂O₄ samples as anode material was studied by fabricating lithium-ion half-cells. NiFe₂O₄ sample obtained from surfactant-free synthesis condition (NFO-S) displayed a high initial discharge and charge capacity of 2258 mAh/g and 1815 mAh/g, respectively at the current density of 100 mA/g. Even after 100 cycles, NFO-S showed a better discharge capacity of 116 mAh/g at the current density of 100 mA/g, compared to the other samples studied here. The observed higher capacity of the NFO-S sample is attributed to the higher surface area (40.8 m²/g) and pore volume (0.190 cm³/g). The NiFe₂O₄ sample prepared with cationic CTAB surfactant (NFO-C) showed better cyclic stability with a stable coulombic efficiency of 98.5% at the 100th cycle, mainly attributed to its nanocube morphology with lower surface area (16.1 m²/g) and pore volume (0.087 cm³/g).

Hydrogen gained momentum as a viable alternative to crude-derived fuels. Scalable production of green hydrogen harnessing solar energy emerged as one of the promising sustainable options that can be facilitated by photocatalyst-assisted water splitting. One-step and two-step photoexcitation systems for overall water splitting (OWS) processes gained much importance because of the ease with which they can be scaled up. This chapter gives a profound insight into the fundamental aspects of these systems, along with a broader picture regarding their possible pathway for commercial implementation. Thermodynamic and kinetic requisites of these novel systems have been described in detail and a critical appraisal of the selectivity of co-catalysts in the photocatalytic OWS process is presented. Subsequently, this chapter provides a comprehensive focus on various novel scalability studies like thin film systems, baggie reactors and the solar hydrogen farm project. The ultimate motive of this chapter is to summarize the current state-of-the-art strategies for producing green hydrogen through heterogeneous photocatalysis and the various limitations it possesses that preclude the system from reaching the market so far. By this it will motivate people to develop innovative pathways that would rectify the problems associated with it.

Electrochemical reduction of carbon dioxide (CO₂) to useful products is an emerging power-to-X concept, which aims to produce chemicals and fuels with renewable electricity instead of fossil fuels. Depending on the catalyst, a range of chemicals can be produced from CO₂ electrolysis at industrial-scale current densities, high Faraday efficiencies, and relatively low cell voltages. One of the main challenges for up-scaling the process is related to (bi)carbonate formation (carbonation), which is a consequence of performing the reaction in alkaline media to suppress the competing hydrogen evolution reaction. The parasitic reactions of CO₂ with the alkaline electrolytes result in (bi)carbonate precipitation and flooding in gas diffusion electrodes, CO₂ crossover to the anode, low carbon utilization efficiencies, electrolyte carbonation, pH-drift in time, and additional cost for CO₂ and electrolyte recycling. We present a critical review of the causes, consequences, and possible solutions for the carbonation effect in CO₂ electrolyzers. The mechanism of (bi)carbonate crossover in different cell configurations, its effect on the overall process design, and the economics of CO₂ and electrolyte recovery are presented. The aim is to provide a better understanding of the (bi)carbonate problem and guide research directions to overcome the challenges related to low-temperature CO₂ electrolysis in alkaline media.

The development of an effective and reliable sensor with the capability to detect ammonia (NH₃) gas at room temperature exerts a significant influence on the sensor industry. The gas sensing performance is notably improved by the formation of a heterostructure between metal oxide with metal sulfides. In this study, pure ZnIn₂S₄ (ZIS), Cu₂O and heterostructures of ZIS with 5, 10 and 20 wt% of Cu₂O were successfully prepared using hydrothermal, co-precipitation and heat treatment methods, respectively. A thorough investigation has been carried out to examine the sensing capabilities of all the materials upon exposure to NH₃ with different concentrations (1, 5, 10, 15, 20, 25 and 50 ppm) at room temperature (RT). Impressively, the composite material 0.9ZnIn₂S₄/0.1Cu₂O (ZIS-10) has exhibited remarkable gas sensitivity compared to pristine ZIS and Cu₂O towards 25 ppm NH₃, low limit of detection (1 ppm) with fast response/recovery times (37/25 sec). The improved performance of the ZIS-10 composite sensor may be ascribed to the synergistic effect between ZIS and Cu₂O, which facilitates the electron transfer from ZIS to the Cu₂O at the interface. The plausible gas-sensing mechanism and the pathways responsible for enhanced sensing are also discussed in detail.

The development of antibacterial coatings is a promising approach to preventing biofilm formation and reducing the overuse of systemic antibiotics. However, widespread antibiotic use has resulted in antibiotic-resistant bacteria, limiting the efficacy of antibiotic-based coatings. Herein, an antibacterial coating is developed by layer-by-layer (LbL) assembly of two polymers namely PDLG (poly (D,L-lactide-co-glycolide)) and gelatin methacryloyl (GelMA) while chicken cathelicidin-2 (CATH-2), a cationic and amphipathic peptide, is loaded between these polymer layers. The electrospray method is used to apply the coatings to achieve efficient peptide loading and durability. The CATH-2 bactericidal concentration ranges are first identified, followed by a study of their cytotoxicity to human mesenchymal stem cells (hMSCs) and macrophage cell lines. Later, different LbL electrospray coating assemblies loaded with the optimal peptide concentration are sought. Various coating strategies are investigated to identify an LbL coating that exhibits prolonged and biocompatible CATH-2 release. The resulting CATH-2-coated titanium surfaces exhibit strong antibacterial activity against both Staphylococcus aureus and Escherichia coli bacteria for 4 days and are biocompatible with hMSCs and macrophage cells. This coating can be considered as a versatile delivery system platform for the delivery of CATH-2 peptides while avoiding cytotoxicity, particularly for the prevention of infections associated with implants.

Fischer-Tropsch synthesis (FTS) is a catalytic reaction, which involves the production of liquid hydrocarbon fuel from synthesis gas obtained from natural gas, biomass or coal via gasification and steam reforming. From an industrial perspective, both Co and Fe based catalysts have been applied. However, Co-based catalysts are preferred in FTS particularly for gas-to-liquid (GTL) processes as they have high activity, high selectivity to linear hydrocarbons and low activity for the unwanted water-gas shift reaction. However, Co-based catalysts are relatively expensive and deactivate in time. To make the FTS process economically more effective, a stable performance of the catalyst is required. Therefore, studying the catalyst deactivation is an important topic in the development of better industrial catalysts. Oxidation, sintering of active phase and deposition of oxygenated compounds are potential causes for deactivation. The possible role of oxygenates and their effect of catalyst deactivation, however, is less understood. With the aim to investigate the deposition of oxygenated compounds, particularly carboxylates, as hypothetical deactivation mechanism, operando characterisation techniques were adapted to monitor the chemical and physical properties and structure-activity relationship of the catalyst during the reaction. Operando Diffuse Reflectance Infrared Fourier Transform (DRIFT) and Mössbauer emission spectroscopy setups were employed that can be operated at industrially relevant FTS conditions.

Operando spectroscopic techniques (Diffusive Reflective Infrared Fourier-Transform and Mössbauer emission spectroscopy) were combined to investigate the role of oxygenates deposition on deactivation of cobalt on titania Fischer-Tropsch catalysts at high pressure. Clear formation of carboxylates was seen for catalysts prepared via both impregnation and precipitation, but more and heavier carboxylates were seen on the impregnated catalyst. This effect is related to a higher olefin content in the products obtained with the impregnated sample, resulting to increased formation of oxygenates through the hydroformylation side reaction. The combined gas chromatography/infrared spectroscopy data demonstrated that the surface carboxylate species are not involved in the catalyst deactivation, being most likely spectator species on the titania support.