Microstructure characterization of W-Ni-Cu heavy alloy fabricated by hydrogen reduction and pressureless sintering of WO3-NiO-CuO powder mixture

Solution combustion and four-stage hydrogen reduction enabling the low-temperature synthesis of ultrafine tungsten‑rhenium alloy powder with decreased rhenium loss

Heterometallic nanoparticles possess immense potential in catalysis and materials science; however, achieving precise structural control remains a major challenge. In this work, we report a facile co-reduction strategy for the preparation of gold-silver (Au-Ag) heterometallic nanoparticles stabilized by multidentate polyoxometalates, which act as functional inorganic ligands. Notably, core-shell-structured Au-Ag nanoparticles are preferentially obtained even under co-reduction conditions, and selective synthesis of either random alloy or core-shell particles is readily achieved by adjusting the Au:Ag precursor ratio. Metal-polyoxometalate interactions generate precursor complexes that direct nanoparticle growth, and metal-specific affinities of polyoxometalate ligands stabilize the resulting structures. The obtained Au-Ag core-shell nanoparticles can be immobilized on carbon supports without significant structural changes and exhibit superior catalytic activity and selectivity in 4-nitrophenol hydrogenation and electrochemical CO2 reduction, outperforming random alloy and monometallic analogues. These findings demonstrate the versatility of polyoxometalate ligands in the structural engineering of heterometallic nanoparticles, opening new directions for the design of advanced catalysts and functional nanomaterials.

Although red phosphorus (RP) is a promising photocatalyst, its performance in simultaneous benzyl alcohol (BA) oxidation and H2 evolution is constrained by undesirable carrier recombination and sluggish surface reaction kinetics. The d-p orbital hybridization, serving as a crucial mechanism for electronic structure regulation, offers an effective strategy to address the aforementioned challenges. Hence, RP is synergistically regulated by defect-rich nickel oxide (NiOx) and Co single atoms (CoSA) to construct a dual d-p orbital hybridized photocatalyst (NiOx@RP@CoSA). In the NiOx@RP@CoSA system, the Ni 3d-P 2p orbital hybridization optimizes the BA adsorption at Ni sites and reducing the C─H bond activation energy barrier. Meanwhile, the Co 3d-P 2p orbital hybridization is conducive to balancing the hydrogen reduction reaction. In situ characterization combined with density functional theory (DFT) calculations confirms that precise regulation of dual d-p orbital hybridization not only enhances charge separation efficiency but also promotes surface reaction kinetics. The 5NiOx@RP@0.2CoSA exhibited superior photocatalytic performance, which is approximately a 15.48-fold enhancements compared to RP. This work not only elucidates the mechanism of dual d-p orbital hybridization but also establishes a novel paradigm for the design of efficient and multifunctional solar-driven catalytic systems.

HighlightsWhat are the main findings?SnS successfully synthesised via ultrasonic spray pyrolysis and H2 reduction.Unique synthesising method that is not replicable via simple solid-gas reaction.Thermochemical calculations of the hydrogen reduction of SnSO4.SnSO4 precursor enables clean, single-step conversion without substrate deposition.XRD confirmed SnS formation with minor SnO2 under 600–800 °C conditions.What are the implications of the main findings?Demonstrates novel powder synthesis for SnS materials.Offers alternatives to conventional thin-film deposition routes.Provides insight into phase evolution during SnSO4-H2 reduction.Simplicity and controllable conversion route.This study presents a novel approach for the synthesis of tin(II) sulphide (SnS) by integrating ultrasonic spray pyrolysis (USP) with hydrogen reduction (HR), using tin(II) sulphate (SnSO4) as a precursor. The method combines aerosol droplet generation using ultrasonic atomisation at 1.7 MHz with gas-phase reduction in a tube reactor under H2-N2 mixed gas flow. Thermochemical assessment indicated that SnS formation is thermodynamically favourable from 400 to 1000 °C, in reasonable agreement with experimental results. XRD analysis confirmed the formation of SnS as the main phase accompanied by SnO2 as a secondary product without SnSO4 when conducting USP-HR at 1000 °C. SEM images revealed flake-like, spherical, and agglomerated morphologies, with EDS confirming distinct Sn-S regions. This study demonstrates the feasibility of producing SnS powder using a simple precursor system and a clean reducing environment. The process offers a scalable and controllable synthesis route for SnS materials, providing an alternative to conventional substrate-based deposition techniques. Further optimisation of reaction temperature and residence time is expected to enhance phase purity and reduce agglomeration.

The growing need for sustainable and efficient energy conversion has driven the development of advanced catalytic materials. In this quest, nanozymes-nanomaterials that mimic the catalytic functions of natural enzymes emerge as promising candidates due to their tunable catalytic properties, high operational stability, and cost-effectiveness. This review presents recent advancements in the applications of nanozymes for clean energy technologies, focusing on their mechanistic roles and engineering strategies within the scope of key reactions, including hydrogen evolution reaction (HER), oxygen evolution and reduction reactions (OER, ORR), CO2 reduction, biofuel production, and methane-to-methanol conversion. The fundamental classes of nanozymes, their structure-activity relationships, and how their fine-tuned properties aid energy conversion in systems such as biofuel cells, electrolyzers, and fuel cells are also discussed. To underscore their practical advantages, nanozymes are benchmarked against conventional catalysts using key performance metrics such as turnover frequency, cost, and stability. Additionally, the review addresses challenges associated with limited selectivity, incomplete mechanistic understanding, and scalability while also highlighting emerging technologies such as nanostructuring, doping, hybridization, and 3D printing. By mapping recent advances and identifying critical research gaps, this review underscores the potential of established nanozymes and nanozyme-inspired catalytic systems as next-generation catalysts for clean energy applications and their role in advancing the transition toward a carbon-neutral and circular energy economy.

We demonstrate that in situ impedance spectroscopy is a marker method to follow LaNiO3 decomposition upon hydrogen reduction and is highly potent for the in situ detection of bulk- and surface-located chemical and structural transitions. Combined with in situ X-ray diffraction (XRD), it simultaneously proved the possibility to assess the electrochemical properties of oxygen-deficient phases and the full decomposition products La2O3 and Ni. In situ correlation of impedance and differential thermoanalytic data allows quantitatively pinpointing distinct exothermic peaks to LaNiO2.5 and La2O3 + Ni formation. The initial impedance increase at low temperatures is related by in situ near-ambient pressure X-ray photoelectron spectroscopy to near-surface redox transformations. Equilibrium impedance investigations revealed a pronounced kinetic delay in the structural transformations at low temperatures. In situ impedance spectroscopy upon redox cycling between reductive (H2) and oxidative (O2) conditions allowed us to clearly discriminate between reversible and irreversible transformations and demonstrated exceptional sensitivity to surface reorganization, including the reoccupation of oxygen vacancies and recompensation of structural defects. Frequency-dependent investigations demonstrate that LaNiO3 exhibits an inductive reactance in O2. Formation of oxygen-deficient LaNiO2.5 and irreversible decomposition into La2O3 + Ni are reflected in the frequency-dependent investigations and expressed via increasing capacitance. p-type semiconduction profoundly influences the impedance behavior of NiO in oxidative and reductive atmospheres and was found to be the key conduction contribution of LaNiO3 decomposition at 600 °C. Our work highlights the strength of in situ impedance spectroscopy as a noninvasive, highly responsive marker for surface chemistry, defect dynamics, and bulk structural transformations during redox experiments in perovskites, as evidenced for LaNiO3.

Thermodynamic modeling combined with experimental reduction tests was conducted to investigate the selective reduction behavior of iron-manganese ore using hydrogen gas at 800–900 °C. The results reveal that hydrogen reduction at a flow rate of 0.5 L/min promotes the stepwise transformation of iron oxides (Fe2O3 → Fe3O4 → FeO → Fe), accompanied by the decomposition of the intermediate spinel phase Fe2MnO4, resulting in the formation of metallic iron. In contrast, the reduction of MnO to metallic manganese is thermodynamically unfavorable (ΔG > 0), limiting the extent of manganese reduction. Experimental findings confirm the formation of metallic iron inclusions enriched in Fe, while manganese predominantly remains in the form of MnO and silicate-associated oxides. X-ray diffraction analysis of reduced samples shows a decrease in Fe3O4 and Fe2MnO4 phases with increasing reduction degree and indicates the growth of metallic Fe particles with rising temperature. These results demonstrate that hydrogen enables controlled and selective reduction of iron with minimal manganese conversion, providing a promising route for subsequent efficient magnetic separation of metallic and oxide phases following reduction roasting.

Study of hydrogen reduction MoO3-to-Mo pathway by dimensions of time and Space

Modeling strategies for hydrogen reduction of high-purity metals: From DFT to ReaxFF and machine learning

Study on hydrogen reduction behavior of Hainan Hematite: Kinetic and microstructural evolution from a green resource processing perspective

Abstract This study synthesized a Mn-based catalyst using a potassium permanganate-assisted precipitation method and investigated its catalytic activity and deactivation behavior in ozone decomposition. The spent catalyst was regenerated via thermal treatment and hydrogen reduction. Ozone decomposition experiments combined with XRD and XPS analyses revealed that the accumulation of surface-adsorbed oxygen species significantly reduced the catalytic activity of Mn-based catalysts by blocking active sites. This accumulation is closely linked to the rate-limiting step in the decomposition mechanism—namely, the desorption of oxygen species. Regeneration methods of spent catalysts were explored using thermal treatment (100–600 °C) and hydrogen reduction (40 °C and 60 °C). Thermal treatment (100–500 °C) restored up to ~ 57.5% of activity at 300 °C, whereas hydrogen reduction at 60 °C achieved ~ 55% recovery under energy-efficient conditions. Notably, hydrogen reduction selectively removed adsorbed oxygen species even at low temperatures, offering a promising alternative to conventional thermal regeneration methods.

Manganese ferroalloys are important alloying additives in steel and aluminium, produced efficiently by carbothermic reduction in Submerged Arc Furnaces (SAF). These processes emit 0.9-1.3 kg CO2/kg Mn ferroalloy [1]. Decarbonising the energy system is a first and very important step, but it will not be enough because carbon dioxide is also a product of the metal-producing reactions themselves. Some relatively mature technologies such as biocarbon reductants and carbon capture and storage or use (CCSU), may allow the industry to move away from fossil CO2 emissions while continuing to use the carbothermic reduction route for ferroalloy production. However, there are many reasons to look beyond these carbon-based solutions and investigate the possibility to completely decarbonise the industry. Electrolytic production of Mn-alloys is the most direct way to electrify and decarbonize process, compared to e.g., hydrogen reduction and metallothermic reduction. Electrolytic manganese metal (EMM), a very pure manganese, is today produced electrochemically through an aqueous electrowinning process, but electrowinning processes producing alloys and with higher throughput is currently under evaluation for several Mn-alloy producers.In this work, a molten oxide electrolysis (MOE) process [2] at 1300-1400 °C with an inert anode for O2 production is investigated as an alternative CO2-free production process of liquid Mn/FeMn/other Mn-alloys from MnO /Mn ores. The suggested process in the attached figure looks similar as aluminium primary production using traditional molten salts, and the MOE process for iron production have been demonstrated by Boston Metal [3]. Advantages of the process include the production of a liquid product (high throughput), no or low emission of halogenides, fines can be used as raw material, low carbon content alloys are produced directly, and less steps before metal production should give a lower capex. The electrowinning process is likely to require pre-reduction of the ore, but this could e.g. be accomplished with H2 [4]. The main challenges are related to the typically high viscosity of the molten oxide melt compared to traditional molten salts, materials selection related to the melt composition and corrosion, the oxidizing atmosphere in the cell which may oxidize the Mn resulting in lower current efficiency, and the high energy consumption related to electrowinning of oxides without carbon.Electrolysis experiments with an electrolyte containing MnO, Al2O3, SiO2, MgO, and CaO with a metal alloy as the oxygen-evolving inert anode have been conducted, using a variation of cathode materials like Mo [5], Fe, and W, at 1250-1450 °C. The process of using MOE and oxygen evolving electrodes was confirmed to be able to produce Mn-alloys using the consumable Mo and Fe cathodes, which appeared easier than producing pure Mn with a more inert cathode material due to the evaporation of metal at the high temperatures.AcknowledgementsThis project has received funding from The Research Council of Norway: Contract number 344259 (ZeSiM). Partners in the project are SINTEF, NTNU, Elkem ASA, Eramet Norway AS, Finnfjord AS and Wacker Chemicals Norway.

Symmetrical solid oxide fuel cells (S-SOFCs) have gained increasing popularity in recent years due to the essential role they can play in energy systems, especially with respect to renewable energy sources. As renewable energy capacity expands globally each year, a trend expected to accelerate the intermittent nature of its electricity production is driving a growing demand for effective energy storage, however current storage technologies are not fully equipped to address this issue [1]. S-SOFCs can serve as a key element in modern energy systems by converting surplus electricity into hydrogen or ammonia in electrolysis when power supply exceeds demand. Later, this stored fuels can be used to generate electricity in fuel cell mode whenever consumption spikes. However, high operating temperatures (>800 °C) pose significant challenges for the commercialization of SOFCs, including, for instance, accelerated cell degradation and thermal stresses [2]. Efforts to reduce the operating temperature to around 700 °C or lower using well-known materials are impeded by the drastic drop in electrode electrochemical performance. Therefore, engineering electrodes that maintain strong electrocatalytic activity under lower-temperature conditions is critical for further developing affordable, high-performance S-SOFCs. In response, there is a growing focus on manufacturing heterostructured electrodes through methods such as mechanical milling, infiltration, in situ assembling, and in situ exsolution of nanoparticles. The key advantage of heterostructured electrodes lies in their capacity for high mixed ionic-electronic conductivity (MIEC) along with enhanced catalytic performance [3-4].In this work, A-site deficient Ln1.8-xSrxFe1.4Ti0.2M0.2Ni0.1Co0.1O6-δ (Ln = Sm, Pr; M = Mo, W, Cr, Mn) perovskites were systematically investigated as new electrode materials for symmetrical SOFCs. In addition, the proposed symmetrical electrode materials present also excellent performance as oxygen electrodes, such as Sr1.8Fe1.4Ti0.2M0.2Ni0.1Co0.1O6-δ cathode with Rp of 0.11 Ω·cm² at 700 °C. It has been found that introducing A-site deficiency almost invariably reduces the polarization resistance (RP) during cathodic operation. For instance, A-site non-stoichiometric Sr1.8Fe1.4Ti0.2Cr0.2Ni0.1Co0.1O6-δ (Rp = 0.072 Ω·cm² at 800°C) shows much lower electrode polarization than the stoichiometric sample (Rp = 0.16 Ω·cm² at 800°C). Moreover, the A-site deficiency and the phase transition from perovskite to Ruddlesden-Popper structure in reducing conditions significantly promote the in situ exsolution of nanoparticles, contributing to the enhanced electrochemical performance of fuel electrodes. Figure 1b illustrates the Sr2Fe1.4Ti0.2Mn0.2Ni0.1Co0.1O6-δ material with in situ exsolved nanoparticles on its surface after a reduction in pure hydrogen. The morphology of electrodes was further optimized by fabricating nanofibers using the electrospinning technique (Fig. 1c), leading to a significant improvement of performance at intermediate temperature range (≤700 °C).

Traditional steelmaking processes consume about 7% of the world’s energy supply, with reduction of iron oxides into iron via blast furnaces representing the most energy-demanding and capital-intensive step. To economize and modularize iron reduction processes, we aim to develop an electrodeposition technique to reduce aqueous iron ions to metallic iron. However, the hydrogen reduction reaction (HER) occurs at a more positive standard reduction potential than the iron reduction reaction. In addition, aqueous Fe(II) cations easily precipitate at mildly acidic conditions (pH ≥ 3), which limits the deposition efficiency and degrades deposit quality.To address these challenges, we first search for anions that have intermediate coordination strength with Fe(II) based on the hard-soft acid-base theory, trading a slightly more negative Fe(II) reduction potential for a considerably broader pH stability range. We select citrate with predicted intermediate coordination strength, in combination with more weakly coordinating anions (e.g., SO4 2-, Cl-) to control the coordination structure of Fe2+ for improved electrolyte stability and electrodeposition behavior. We find that citrate coordination stabilizes Fe2+-based electrolytes at higher pH conditions (4.8–5.5), significantly extending their shelf life while also suppressing HER during Fe electrodeposition by orders of magnitude. To measure Faradaic efficiencies (FE), we developed a straightforward, titration-based methodology to quantify the amount of deposited iron regardless of the rate of concurrent HER. Although coordination between citrate and Fe2+ decreases the reduction potential of Fe(II), high FE (≥98%) was achieved at 10 mA cm-2. FE and achievable deposition rates are tunable by both concentration and the ratio of Fe2+ to citrate. In all cases, Raman spectroscopy and X-ray diffraction (XRD) reveal that iron deposition in citrate-containing electrolytes suppresses iron oxide/hydroxide precipitation, in contrast to deposits generated in citrate-free electrolytes.Overall, this work demonstrates that citrate-mediated anion coordination enables high-purity iron electrodeposition with increased FE, high current density, and improved electrolyte stability. This multi-anion coordination strategy provides a versatile framework for designing stable electrolyte and efficient metal electrodeposition.

The preservation of our planet is the most urgent issue in the world and the scientific community is pushing a lot of researchers to work on technologies for the storage/conversion of CO2 into chemicals. However, it is easier not to produce CO2 than setting-up plants to treat it.In this framework, the ERC-StG project SuN2rise proposes an alternative breakthrough based on a versatile solar-driven strategy leading to redesign industrial processes. Facing the Haber-Bosch process for ammonia production (one of the most impactful chemical processes today), we propose the electrochemical fixation of dinitrogen into ammonia, by simply using air, water and ambient conditions. The scientific aim is that of demonstrating an integrated device where a photovoltaic (PV) unit will power a regenerative electrocatalytic cell converting dinitrogen to ammonia (E-NRR). A newly proposed Li-mediated approach under mild conditions, derived from an interdisciplinary contamination between electrocatalysis and Li-batteries, will be the key towards N2 conversion, bypassing both the competitive hydrogen reduction reaction and the complete irreproducibility of recent E-NRR approaches attributed to N-contaminations or degradation of N-based catalysts.Electrolytes play a crucial role in the electrochemical production of ammonia via nitrogen reduction, directly influencing efficiency, selectivity, and stability of the process [1-3]. They facilitate ion transport, optimize reaction kinetics, and help stabilize active sites on the electrocatalyst. The choice of electrolyte affects the proton availability, which is essential for the reduction pathway, while also preventing competing hydrogen evolution. Advanced ionic liquids, deep eutectic solvents, and tailored aqueous solutions are being explored to enhance nitrogen solubility and improve reaction yields. Developing high-performance electrolytes is key to making electrochemical ammonia synthesis a viable and sustainable alternative to the Haber-Bosch process.The team will further move beyond the state-of-the-art by fabricating transparent devices, that can be integrated in greenhouses, allowing the production of ammonia and ammonium fertilizers directly in farms, bypassing the known issues related to the massive infrastructure of ammonia plants and difficulties in reaching remote communities. The proposed approach will significantly impact also the field of liquid fuels, being ammonia safer and with higher energy density than hydrogen. Achieving these goals will require multidisciplinary expertise in the field of chemical, material, process and device engineering. Acknowledgements This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 948769, project title: SuN2rise).

Iron and its alloy is the second most-produced material by human society and is a pillar of modern society. However, the current ironmaking process is not sustainable due to the heavy use of fossil fuel as the reductant and energy source for reducing iron ore. Two routes have emerged to address this challenge. One is direct hydrogen reduction, which uses hydrogen sourced from renewable energy to reduce iron ore. Another is direct electrolytic reduction using renewable electrons. Depending on the electrolytes, various electrolytic routes are possible. Molten-oxide electrolysis enables high current operation, but suffers from challenges such as low efficiency, corrosion, heat loss, etc. Low-temperature electrolysis can avoid some of these challenges. Alkaline electrolysis has been studied for over a decade and has been demonstrated in several projects in European Union and in US. However, acidic electrolysis has received much less attention.In this talk, we will discuss the opportunities and challenges of acidic electrolysis, and present our results in addressing one of the critical challenges of acidic electrolysis, the low faradaic efficiency due to the competing hydrogen evolution reactions. We will share our results in high-efficiency electrowinning of iron metal, discuss the fundamental science underlying the unprecedented efficiency, and opportunities and gaps of designing practical ironmaking process based on acidic electrolysis.

The catalytic versatility of the copper surface calls for a fundamental understanding of the formation and reactivity of key intermediates in various C1 catalytic conversions such as water-gas shift reaction, CO/CO2 hydrogenation, and electrochemical reduction reactions. Here, based on in situ spectroscopic and morphological evidence, we demonstrate the formation of a bridge CO* species through the adsorption-induced restructuring of a defect-rich Cu surface and its reactivity toward C-O bond dissociation and C-C coupling under hydrogenation reaction conditions. In corroboration with computational simulations, we attribute the unexpected reactivity to its enhanced adsorption strength and polarity with respect to commonly observed on-top CO* species. Our findings provide new insights into the strong correlation between the surface defect density and the selectivity toward methane, C2 hydrocarbons, and oxygenates over Cu-based catalysts. The marked impact on reactivity highlights the crucial role of dynamic surface restructuring in determining the reaction selectivity over copper-based catalysts.

Abstract A high-Fe weathered carbonatite RE flotation tailings sample was examined for its potential for iron recovery while simultaneously enriching the rare earth elements (RE) in the residue. The sample contained 48.5 pct Fe 2 O 3 and 8.4 pct total REO, with the main Fe-rich mineral being goethite (FeO.OH) and with RE mainly in a monazite (RE-PO 4 ) phase. Hydrogen was tested as a possible reductant at high temperatures to investigate the reduction and metallization behavior of iron in the goethite. In situ high-temperature X-ray diffraction (HTXRD) analysis results from heating the sample to 1000 °C in an inert atmosphere showed that the goethite was transformed into hydro-hematite (Fe 2−x (OH) x O 3−x ) and then hematite (Fe 2 O 3 ). Following a comprehensive thermodynamic assessment to understand the iron reduction mechanism by hydrogen and its potential interaction with RE-phosphate phases, hydrogen reduction experiments were carried out at 700 °C, 800 °C, 900 °C, and 1000 °C for 4 hours in a vertical tube furnace using a 50:50 mix of H 2 and Ar gases. Characterization results showed that the iron in the goethite was reduced into metallic Fe, Fe(P), and Fe 3 P, depending on the reduction temperature and duration, although some Fe remained in fayalite and hercynite phases. The implications for iron recovery from the reduced tailings are discussed.

Nonthermal plasma (NTP) technology is emerging as a transformative engineering tool for the rational design and synthesis of advanced catalysts, addressing the critical limitations of conventional high-temperature preparation methods. Operating under mild conditions, the unique nonequilibrium environment of NTP-rich in energetic electrons, ions, and reactive radicals-enables precise, multiscale control over catalyst properties. This allows for the creation of highly dispersed nanoparticles, tailored defect structures, and enhanced metal-support interactions that are often inaccessible via traditional thermal routes. This review provides a comprehensive overview of recent progress in applying NTP specifically as a synthesis and modification strategy to engineer high-performance catalysts for the valorization of key greenhouse gases, namely CO2 and CH4. We focus on how these NTP-engineered catalysts exhibit superior activity, selectivity, and stability in critical reactions, including CO2 hydrogenation, electrocatalytic and photocatalytic CO2 reduction, and methane reforming. By elucidating the structure-performance relationships established through plasma-based engineering, this review highlights the unique advantages of NTP in catalyst design and provides insights for the development of next-generation catalysts for sustainable chemical production.