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This study explores the use of biomass-based carbon aerogels from raspberry pulp as electrocatalysts for the hydrogen evolution reaction (HER). Producing hydrogen via alkaline water electrolysis, from renewable energy sources, is an attractive way to mitigate climate change; however, there still exists challenges in achieving high efficiency without resorting to expensive noble metal catalysts. HER electrocatalysts from transition metal-doped biomass are promising, cost efficient, durable and renewable alternative materials. Freeze dried raspberry pulp with added iron salts was pyrolyzed, resulting in carbon aerogels containing iron oxide nanoparticles. These nanoparticles were later used to grow carbon nanotubes (CNTs) by chemical vapor deposition which enhanced HER activity with overpotential reaching only 408 mV at a current density of −10 mA cm−2, an increase in performance by 30% when compared to that of aerogels without CNTs. This shows that our synthetic approach is effective for catalysis applications, and its versatility means that efficiency could be improved further by tuning the properties of iron oxide nanoparticles and the three-dimensional interconnected porous network of the carbon aerogel.

Efficient electrocatalysts are vital for advancing sustainable fuel cell technology, and the use of affordable alternatives that enhance the reaction kinetics is key to progress. Although, tungsten diselenide (WSe2) is promising for electrocatalysis, it is not fully explored, especially in oxygen evolution and in applications such as polymer electrolyte membrane water electrolyzer. In this work, we use a simple approach to dope WSe2 with cobalt or nickel atoms. Both Co- and Ni-WSe2 exhibit excellent oxygen evolution reaction activity, with overpotentials of 370 and 400 mV at 10 mA/cm2, only 90 and 120 mV higher than those of RuO2, respectively. For hydrogen evolution reaction, the materials register low potentials at −10 mA/cm2, with −0.20 V and −0.22 V vs RHE for Ni- and Co-WSe2, respectively. The effective introduction of heteroatoms causes the retention of coordination vacancies, furnishing active catalytic sites that enhanced electrocatalytic performance, resembling this of noble metals in both activity and charge transfer. Moreover, both doped materials show excellent performance and stability as cathode electrocatalysts in the polymer electrolyte membrane water electrolyzer, with great promise for real-world applications. This study promotes sustainable fuel-cell technology through the development of cost-effective, doped WSe2 electrocatalysts that improve water splitting and hydrogen production efficiency.

Trimetallic nickel–iron–molybdenum oxides are excellent electrocatalysts for alkaline water electrolysis despite experiencing severe molybdenum dissolution. While the impact of molybdenum on fresh samples is well-understood, its substantial loss during operation without compromising performance presents a unique puzzle. Here, we show that the initial presence of molybdenum induces the formation of nickel vacancies and distorts octahedral nickel sites. This structural distortion induces charge transfer between lattice oxygen and nickel, inducing an early formation and stabilization of active nickel oxyhydroxides. Even after complete molybdenum leaching and transitioning into a bimetallic nickel-iron oxide, the catalyst retains its exceptional performance due to the persistence of distorted octahedral nickel sites. Understanding this process enables the exploration of alternative metals that could induce similar structural distortions, as well as inspire similar strategies in other electrocatalysts. (Figure presented.)

Nitrogen-doped sponge carbon nanotubes (SCNTs) are synthesized using catalytic chemical vapor deposition (CCVD). In the CCVD experiment, a catalyst precursor composed of hematite, silicon oxide, and copper is exposed to the pyrolysis of toluene and N, N-dimethylformamide solution for one hour at a growth temperature of 950 °C. The effect of Cu concentration in the catalyst on the yield and morphology of the SCNTs is investigated. The SCNTs are characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The synthesized SCNTs exhibit tangled carbon nanotubes (CNTs) with rough surfaces. The incorporation of Cu induces notable morphological changes in the SCNTs, increasing their surface roughness and diameter, reaching a maximum of 102 nm. Cyclic voltammetry measurements demonstrate that the electrochemical surface area for acid-treated SCNTs is 731.85 cm² cm⁻²geo, whereas pristine SCNTs exhibit 23.34 cm² cm⁻²geo. The catalytic performance of the SCNTs in the hydrogen evolution reaction (HER) is evaluated. Although the initial presence of Cu negatively affects the HER activity, acid treatment mitigates this drawback. The optimized sample reaches an overpotential of 368 mV at −10 mA cm⁻².

A novel one-step chemical vapor deposition approach is introduced for synthesizing high-density vertical molybdenum disulfide (MoS2) nanoflakes and molybdenum dioxide (MoO2) structures using pelletized MoO3/S precursors and abrupt thermal cycling. Unlike conventional multi zone sulfurization methods, the process compacts alternating MoO3/S/MoO3/S/MoO3 layers into 10-ton pressure pellets, ensuring uniform precursor distribution and phase selectivity. Rapid thermal cycling, with an abrupt transition from 25 to 750 °C, followed by rapid cooling after a 5-min deposition under an Ar/H2 flow, critically influences the crystallization dynamics. A sulfur-to-MoO3 molar ratio of 2:1 promotes vertical MoS2 growth (≈100 flakesµm−2), whereas a 1.16:1 ratio induces MoO2 formation with elongated hexagonal morphologies, sizes between (0.70–1.36 µm). This scalable synthesis method offers a reproducible and efficient alternative for nanomaterial fabrication, allowing the production of vertical MoS2 flakes and enlarged MoO2 for transfer onto various substrates, as well as uniform vertical structures directly deposited on the substrate. The findings offer key insights into precursor structuring and thermal modulation for the tailored synthesis of 2D materials with applications in catalysis, energy storage, and nanoelectronics.

The increasing demand for green hydrogen is driving the development of efficient and durable electrocatalysts for the hydrogen evolution reaction (HER). Nickel-molybdenum (NiMo) alloys are among the best HER electrocatalysts in alkaline electrolytes, and here we report a scalable solution precursor plasma spraying (SPPS) process to produce the highly active Ni4Mo electrocatalysts directly onto metallic substrates. The NiMo coating coated onto inexpensive Ni mesh revealed an excellent HER performance with an overpotential of only 26 mV at −10 mA cm⁻² with a Tafel slope of 55 mV dec⁻¹. Excellent operational stability with minimum changes in overpotential were also observed even after extensive 60 hour high-current stability test. In addition, we investigate the influence of different substrates over the catalytic performance and operational stability. We also proposed that a slow, but consistent, dissolution of Mo is the primary degradation mechanism of NiMo-based coatings. This unique SPPS approach enables the scalable production of exceptional NiMo electrocatalysts with remarkable activity and durability, positioning them as ideal cathode materials for practical applications in alkaline water electrolysers.

Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) were synthesized via aerosol-assisted catalytic chemical vapor deposition (AAC-CVD) using earth-abundant catalysts composed of hematite, quartz, and varying amounts of nickel. The effects of nickel concentration and synthesis temperature (750–950 °C) were systematically evaluated to optimize the structural, morphological, and electrochemical properties of the resulting nanomaterials. The CT2-Ni catalyst (9 wt % Ni) demonstrated the highest production efficiency, reaching ∼280 %, and promoted the growth of thin entangled nanotubes with average diameters as low as 35.5 nm. Raman spectroscopy revealed significant structural disorder at lower temperatures (ID/IG = 0.93 for CT1-750), which correlated with enhanced catalytic activity. Electrochemical measurements showed that N-MWCNTs synthesized at 750 °C delivered high current densities of >100 mA cm−2 at −0.6 V vs. RHE, supported by favorable electrochemical parameters such as low charge-transfer resistance (22.9 Ω) and high double-layer capacitance (5.25 mF cm−2). These results highlight the synergistic effect between Ni doping and defect engineering in optimizing the HER activity. The materials developed in this study offer a scalable and cost-effective alternative to noble-metal-based catalysts, bridging the gap between fundamental research and industrial hydrogen production. This study confirms that a strategic catalyst design using common oxides can drive sustainable energy solutions.

Solar water splitting, through electrocatalysis, photoelectrocatalysis, and photocatalysis, presents a promising pathway for converting abundant solar energy into clean hydrogen fuel. However, to meet the increasing demand for green hydrogen, catalysts for the water splitting reaction must not only achieve high efficiency but also be primarily composed of abundant materials with minimal environmental impact. Understanding the interplay between surface properties, optical properties, and chemical reactivity is crucial to identify suitable alternative materials capable of achieving high solar-to-hydrogen conversion. In this chapter, we discuss the fundamentals of electrochemical, photoelectrochemical, and photocatalytic water splitting. We explore how material’s properties and surface characteristics influence the hydrogen evolution reaction and oxygen evolution reaction. We revise their working principles and key concepts, from light absorption and charge separation to surface characteristics and adsorption energies. Additionally, we discuss key physical, chemical, and optical properties of electrodes and photoelectrodes that are crucial for an efficient water splitting, while presenting strategies for achieving high performance.

Fentanyls are synthetic opioids up to 10,000 times more potent than morphine. Although initially developed for medical applications, fentanyl and its analogues have recently grown synonymous with the ongoing opioid epidemic. To combat the continued spread of these substances, there is a need for rapid and sensitive techniques for chemical detection. Surface-enhanced Raman spectroscopy (SERS) has the potential for trace detection of harmful chemical substances. However, vibrational spectra obtained by SERS often differ between SERS substrates, as well as compared with spectra from normal Raman (NR) spectroscopy. Herein, SERS and NR responses from two fentanyl analogues, carfentanil (CF) and thiofentanil (TF), were measured and analysed with support from density functional theory (DFT) modelling. Using commercially available silver nanopillar SERS substrates, the SERS signatures of samples diluted in acetonitrile between 0.01 and 1000 µg/mL were studied. Relative SERS peak intensities measured in the range of 220–1800 cm−1 vary with concentration, while SERS and NR spectra largely agree for CF at higher concentrations ((Formula presented.) 100 µg/mL). For TF, three distinct NR peaks at 262, 366 and 667 cm−1 are absent or strongly suppressed in the SERS spectrum, attributed to the lone-pair electrons of the thiophene's sulphur atom binding to the Ag surface. The concentration dependence of the Raman peak at (Formula presented.) 1000 cm−1, assigned to trigonal bending of the phenyl ring, approximately follows a Langmuir adsorption isotherm. This work elucidates similarities and differences between SERS and NR in fentanyl detection and discusses the chemical rationale behind these differences.

Understanding “efficiency roll-off” (i.e., the drop in emission efficiency with increasing current) is critical if efficient and bright emissive technologies are to be rationally designed. Emerging light-emitting electrochemical cells (LECs) can be cost- and energy-efficiently fabricated by ambient-air printing by virtue of the in situ formation of a p-n junction doping structure. However, this in situ doping transformation renders a meaningful efficiency analysis challenging. Herein, a method for separation and quantification of major LEC loss factors, notably the outcoupling efficiency and exciton quenching, is presented. Specifically, the position of the emissive p-n junction in common singlet-exciton emitting LECs is measured to shift markedly with increasing current, and the influence of this shift on the outcoupling efficiency is quantified. It is further verified that the LEC-characteristic high electrochemical-doping concentration renders singlet-polaron quenching (SPQ) significant already at low drive current density, but also that SPQ increases super-linearly with increasing current, because of increasing polaron density in the p-n junction region. This results in that SPQ dominates singlet-singlet quenching for relevant current densities, and significantly contributes to the efficiency roll-off. This method for deciphering the LEC efficiency roll-off can contribute to a rational realization of all-printed LEC devices that are efficient at highluminance.