Solid-state Reduction Research Articles

Investigation of High Entropy Alloy Nanoparticles Assisted By Resonance Acoustic Mixing for Oxygen Reduction Reaction

High-entropy alloy (HEA) nanoparticles (NPs) are highly promising for electrocatalysis because of their wide range of compositions, adaptable active sites, and robust stability. Nevertheless, synthesizing these complex compositions as uniform NPs remains a challenge by conventional synthesis methods due to variations in reduction rates among metal precursors, leading to phase separation. This study presented a straightforward and scalable method for producing HEAs using a liquid-assisted (LA) solid-state reduction followed by an annealing process. Employing a resonance acoustic mixer (RAM), this process provides a rapid and scalable means for producing dispersed HEA NPs on carbon support. Quinary HEA (PtNiCuCoZn) catalysts were synthesized by initial mixing and reduction using RAM and further annealing under nitrogen at 900 ℃, sequentially. The resulting HEA electrocatalysts have a narrow particle size distribution with minimal particle agglomeration and demonstrate enhanced mass activity (0.75 A/mgPt) and stability toward oxygen reduction reaction (ΔE1/2=16 mV after 10k cycles), outperforming conventional Pt/C catalysts (~0.2 A/mgPt) while achieving superior Pt utilization.

Scalable Solid-State Synthesis of Carbon-Supported Ir Electrocatalysts for Acidic Oxygen Evolution Reaction: Exploring the Structure-Activity Relationship.

Enhancing iridium (Ir)-based electrocatalysts to achieve high activity and robust durability for the oxygen evolution reaction (OER) in acidic environments has been an ongoing mission in the commercialization of proton exchange membrane (PEM) electrolyzers. In this study, we present the synthesis of carbon-supported Ir nanoparticles (NPs) using a modified impregnation method followed by solid-state reduction, with Ir loadings of 20 and 40 wt % on carbon. Among the catalysts, the sample with an Ir loading of 20 wt % synthesized at 1000 °C with a heating rate of 300 °C/h demonstrated the highest mass-normalized OER performance of 1209 A gIr-1 and an OER current retention of 80% after 1000 cycles of cyclic voltammetry (CV). High-resolution STEM images confirmed the uniform dispersion of NPs, with diameters of 1.6 ± 0.4 nm across the support. XPS analysis revealed that the C-O and C═O peaks shifted slightly toward higher binding energies for the best-performing catalyst. In comparison, the metallic Ir state shifted toward lower binding energies compared to other samples. This suggests electron transfer from the carbon support to the Ir NPs, indicating a potential interaction between the catalyst and the support. This work underscores the strong potential of the solid-state method for the scalable synthesis of supported Ir catalysts.

Preparation of Nickel–Iron Concentrate from Low-Grade Laterite Nickel Ore by Solid-State Metalized Reduction and Magnetic Separation

In this paper, the process of solid-state metalized reduction and magnetic separation was investigated for preparation of nickel–iron concentrate from a low-grade laterite nickel ore. The effects of reduction temperature, reduction time, amount of dosages, and magnetic field strength on grades and recoveries of nickel and iron were studied. The results showed that nickel–iron concentrate with a nickel grade of 7.32%, nickel recovery of 81.84%, iron grade of 78.74%, and iron recovery of 69.78% were obtained under the conditions of a reduction temperature of 1200 °C, reduction time of 120 min, calcium fluoride addition of 12%, ferric oxide addition of 10%, coal addition of 12%, and magnetic field strength of 170 kA/m.

A new method to recycle Li-ion batteries with laser materials processing technology

Efficient and cost-effective recycling of spent lithium-ion batteries is essential for the sustainable growth of the clean energy sector, conserves critical mineral resources, and contribute to environmental sustainability. The pyrometallurgy process, involving high-temperature smelting and solid-state reduction, plays a key role in the industrial-scale recycling of these batteries. Traditional smelting methods, however, face criticism for their substantial energy requirements and the loss of lithium in slag. In this study, an innovative laser-based in-situ pyrometallurgical process, hereinafter referred to as laser recycling, was developed to recycle Li-ion batterie materials without using slag, enabling the simultaneous recovery of Co, Ni, Mn, and Li. Lab-scale experiments were carried out to investigate the influences of laser power density and duration on the carbothermic reduction behavior of battery materials. The results showed that the maximum temperature reached approximately 1850 °C with a laser power between 1500 and 2000 W focused to an area of 20 mm in diameter within a few seconds. The laser recycling facilitates concurrent smelting and solid-state reduction, with carbothermic reduction completed in just 30 s due to rapid reaction kinetics, ultra-high temperatures, and the enhanced contact area resulting from surface tension-driven molten material flow under intense laser beam exposure. This laser recycling process reduced LiCoO2 and LiNi0.33Mn0.33Co0.33O2 to metallic Co or Co-Ni-Mn alloy, respectively, while Li was recovered as Li2CO3. The new process allowed for the near-total recovery of Co, Ni, and Mn in the alloy and virtually 100% Li recovery in the form of Li2CO3 by a vapor phase capture system. Additionally, continuous laser recycling in the battery material powder bed showed potentials to scale up for industry battery recycling. A mechanism for the laser recycling process was proposed. A preliminary discussion on the techno-economic implications of laser recycling was also provided.

Green and solid state reduction of GO monolayers sandwiched between Arachidic acid LB layers

A novel, single step and environment friendly solid state approach for reduction of graphene oxide (GO) monolayers has been demonstrated, in which, arachidic acid/GO/arachidic acid (AA/GO/AA) sandwich structure obtained by Langmuir-Blodgett (LB) technique was heat treated at moderate temperatures to obtain RGO sheets. Heat treatment of AA/GO/AA sandwich structure at 200 °C results in substantial reduction of GO, with concurrent removal of AA molecules. Such developed RGO sheets possess sp2-C content of ∼69 %, O/C ratio of ∼0.17 and significantly reduced I(D)/I(G) ratio of ∼1.1. Ultraviolet photoelectron spectroscopy (UPS) studies on RGO sheets evidenced significant increase in density of states in immediate vicinity of Fermi level and decrease in work function after reduction. Bottom gated field effect transistors fabricated with isolated RGO sheets displayed charge neutrality point at a positive gate voltage, indicating p-type nature, consistent with UPS and electrostatic force microscopy (EFM) measurement results. The RGO sheets obtained by heat treatment of AA/GO/AA sandwich structure exhibited conductivity in the range of 2–7 S/cm and field effect mobility of 0.03–2 cm2/Vs, which are comparable with values reported for RGO sheets obtained by various chemical/thermal reduction procedures. The extent of GO reduction is determined primarily by proximity of AA molecules and found to be unaltered with either escalation of heat treatment temperature or increase of AA content in sandwich structure. The single-step GO reduction approach demonstrated in this work is an effective way for development of RGO monolayers with high structural quality towards graphene-based electronic device applications.

Solid State Reduction Driven Synthesis of Mn Containing Multi-principal Component Alloys

Solid State Reduction Driven Synthesis of Mn Containing Multi-principal Component Alloys

Solid State Reduction and Magnetic Properties of Iron Oxide-Iron System Induced by Ball Milling Process

Solid State Reduction and Magnetic Properties of Iron Oxide-Iron System Induced by Ball Milling Process

Thermal Kinetics and Nitriding Effect of Ammonia-Based Direct Reduction of Iron Oxides.

Ammonia is a promising alternative hydrogen carrier that can be utilized for the solid-state reduction of iron oxides for sustainable ironmaking due to its easy transportation and high energy density. The main challenge for its utilization on an industrial scale is to understand the reaction kinetics under different process conditions and the associated nitrogen incorporation in the reduced material that originates from ammonia decomposition. In this work, the effect of temperature on the reduction efficiency and nitride formation is investigated through phase, local chemistry, and gas evolution analysis. The effects of inherent reactions and diffusion on phase formation and chemistry evolution are discussed in relation to the reduction temperature. The work also discusses nitrogen incorporation into the material through both spontaneous and in-process nitriding, which fundamentally affects the structure and chemistry of the reduced material. Finally, the effect of nitrogen incorporation on the reoxidation tendency of the ammonia-based reduced material is investigated and compared with that of the hydrogen-based reduced counterpart. The results provide a fundamental understanding of the reduction and nitriding for iron oxides exposed to ammonia at temperatures from 500 to 800 °C, serving as a basis for exploitation and upscaling of ammonia-based direct reduction for future green steel production.

Small Copper Nanoclusters Synthesized through Solid-State Reduction inside a Ring-Shaped Polyoxometalate Nanoreactor.

Cu nanoclusters exhibit distinctive physicochemical properties and hold significant potential for multifaceted applications. Although Cu nanoclusters are synthesized by reacting Cu ions and reducing agents by covering their surfaces using organic protecting ligands or supporting them inside porous materials, the synthesis of surface-exposed Cu nanoclusters with a controlled number of Cu atoms remains challenging. This study presents a solid-state reduction method for the synthesis of Cu nanoclusters employing a ring-shaped polyoxometalate (POM) as a structurally defined and rigid molecular nanoreactor. Through the reduction of Cu2+ incorporated within the cavity of a ring-shaped POM using H2 at 140 °C, spectroscopic studies and single-crystal X-ray diffraction analysis revealed the formation of surface-exposed Cu nanoclusters with a defined number of Cu atoms within the cavities of POMs. Furthermore, the Cu nanoclusters underwent a reversible redox transformation within the cavity upon alternating the gas atmosphere (i.e., H2 or O2). These Cu nanoclusters produced active hydrogen species that can efficiently hydrogenate various functional groups such as alkenes, alkynes, carbonyls, and nitro groups using H2 as a reductant. We expect that this synthesis approach will facilitate the development of a wide variety of metal nanoclusters with high reactivity and unexplored properties.

Deformation Microstructure, Metallic Iron, and Inclusions of Hollow Negative Crystals in Olivine from the Seymchan Pallasite: Evidence of Fe2+ Solid-State Reduction

Deformation Microstructure, Metallic Iron, and Inclusions of Hollow Negative Crystals in Olivine from the Seymchan Pallasite: Evidence of Fe2+ Solid-State Reduction

Self-Assembly of Silicon Nanotubes Driven by a Biphasic Transition from the Natural Mineral Montmorillonite in Molten Salt Electrolysis.

Silicon nanotubes (SNTs) have been considered as promising anode materials for lithium-ion batteries (LIBs). However, the reported strategies for preparing SNTs generally have special requirements for either expensive templates or complex catalysts. It is necessary to explore a cost-effective and efficient approach for the preparation of high-performance SNTs. In this work, a biphasic transformation strategy involving "solid-state reduction" and "dissolution-deposition" in molten salts is developed to prepare SNTs using montmorillonite as a precursor. The rod-like intermediate of silicon-aluminum-calcium is initially reduced in solid state, which then triggers the continuous dissolution and deposition of calcium silicate in the inner space of the intermediate to form a hollow structure during the subsequent reduction process. The transition from solid to liquid is crucial for improving the kinetics of deoxygenation and induces the self-assembly of SNTs during electrolysis. When the obtained SNTs is used as anode materials for LIBs, they exhibit a high capacity of 2791mAhg-1 at 0.2Ag-1, excellent rate capability of 1427mAhg-1 at 2Ag-1, and stable cycling performance with a capacity of 2045mAhg-1 after 200 cycles at 0.5Ag-1. This work provides a self-assembling, controllable, and cost-effective approach for fabricating SNTs.

Kinetics of solid-state reduction of chromite overburden

Kinetics of solid-state reduction of chromite overburden

Thermodynamic and kinetic aspect of solid state reduction of Electric Arc Furnace slag through coke: An experimental study.

Steel slag is one of the major wastes produced during the steelmaking process. In the present scenario, the world’s utilization rate of steel slag is comparatively very low and primarily used for landfills only. The untreated slag used for the dumping will affect the environment adversely and causes loss to the economy as well. In the present study, we are concentrating on steel slag through the latter. The mineralogy of primary slag ensures the presence of various constituent ranges, Fe2O3 /FeO (18–30%), CaO (23–48%), SiO2 (2–6%), MgO (4–17%), and Al2O3 (2–15%), mainly depends on the quality of raw material as well as processing relies on the quality of raw material as well as processing. One of the significant components of steel slag with a large variety of ranges is iron oxides. Iron Oxide is present in the steel slag in the form of FeO, Fe2O3, and FeO.SiO2. This study analyzed the reduction kinetics of steel slag based on the Coats-Redfern method and explained the reduction mechanism of Fayalite for different slag basicity. The investigation involves a temperature range of 960–1478 K with a carbon-to-oxygen ratio of C/O-1.The non-isothermal experiment covers the solid reduction of EAF slag. The TG curve shows the reduction reaction of steel slag and coke from 0.5 to 1.5 is 7.31% to 10.88%. During the investigation, the activation energy of iron reduction process will get decrease with increased slag basicity.

Solid-state processed novel germanium/reduced graphene oxide composite: Its detailed characterization, formation mechanism and excellent Li storage ability

By using a simple solid-state reduction process, germanium oxide (GeO2) and graphene oxide (GO) are reduced to germanium (Ge) and reduced graphene oxide (rGO), respectively, to form Ge/rGO composite. Transmission electron microscopy showed that clusters of Ge nanoparticles are decorated on the graphene layers of rGO. Detailed x-ray diffraction, Raman scattering, and x-ray photoelectron spectroscopic analyses confirmed Ge/rGO composite formation. The thermal stability of Ge/rGO composite and the reduction mechanism through which the composite is formed are experimentally elucidated. Further, Brunauer–Emmett–Teller (BET) specific surface area, average pore volume, and average pore size of Ge/rGO composite are measured to be ∼115 m2/g, ∼0.4 cm3/g, and ∼14 nm, respectively. The thermal analysis quantified the amount of rGO in the Ge/rGO composite to be ∼66%. As-synthesized Ge/rGO composite is tested as anode material in Li-ion batteries. When cycled at 160 mA/g current density and in the 0.005–3.0 V voltage range, the composite showed an excellent reversible capacity of ∼539 mAh/g that corresponds to 98% capacity retention at the end of the 100th cycle. The Ge/rGO composite also showed high reversible capacity retention, good rate capability, and excellent cycle life when tested at 80 and 320 mA/g in the same voltage range. The redox peaks in the cyclic voltammetry (CV) curves revealed that alloying-dealloying and electrochemical adsorption-desorption mechanisms are the primary reasons for the lithium-ions storage by Ge and rGO, respectively. A constant area under the CV curves throughout the test indicated the stable capacity. Also, the CV results align with the galvanostatic cycling results.

Effect of Si on the hydrogen-based direct reduction of Fe2O3 studied by XPS of sputter-deposited thin-film model systems

Understanding the effect of gangue elements is of critical importance to optimize the efficiency of hydrogen-based direct reduction (HyDR) of iron ore, as one of the key steps towards climate-neutral steel production. Here, we demonstrate on the example of Si-doped Fe2O3, how thin films can be effectively utilized as a model system to facilitate systematic investigation of the solid-state reduction behavior. In-vacuo X-ray photoelectron spectroscopy (XPS) is used to probe the reduction kinetics by analyzing the chemical state of iron oxide thin films before and after annealing at 700 °C in an Ar+5%H2 atmosphere. It is demonstrated that even low Si concentrations of 3.7 at.% inhibit the HyDR of Fe2O3 by the formation of a SiOx-enriched reduction barrier in the surface-near region.

Boosting electrocatalytic performance and durability of Pt nanoparticles by conductive MO2−x (M = Ti, Zr) supports

Metal oxides, especially TiO2, have been studied as an alternative support to replace the carbon in the conventional Pt/C catalysts for their high electrochemical stability at high electrode potentials. The low conductivity of metal oxides has been a big hurdle. In this work, we successfully overcome this issue by forming conductive MO2−x (M = Ti and Zr) through solid state reduction with NaBH4. The temperature of the reaction has turned out to be a crucial parameter to obtain highly conductive MO2−x. Pt/MO2−x catalysts were prepared by depositing Pt nanoparticles (NPs) on MO2−x supports whose analysis data, show that the Pt NPs are uniformly deposited on the surface of MO2−x supports and that there is a strong electronic interaction between Pt NPs and MO2−x supports. The electrocatalysis of Pt/MO2−x catalysts for oxygen reduction reaction (ORR) has been studied. Pt/MO2−x catalysts show significantly enhanced mass activity (MA) and specific activity (SA) from those of Pt/C catalyst. More importantly, Pt/MO2−x catalysts show a superior long-term durability. After 50,000 cycles of durability test, Pt/T370 catalyst retains 75%/84% of initial MA/SA, and Pt/Z438 catalyst retains 81%/88% of initial MA/SA, while Pt/C catalyst keeps only 36%/56% of initial MA/SA after 30,000 cycles. The significantly enhanced ORR performance of Pt/MO2−x catalysts is attributed to the strong metal-support interaction (SMSI) effect between MO2−x and Pt NPs as well as the high conductivity of MO2−x supports. We believe Pt/MO2−x catalysts are a promising form of electrocatalysts that can replace the presently dominating but not quite satisfactory Pt/C in fuel cell applications.

Solid state reduction of nickelate thin films

The square-planar nickelates are a class of superconductors analogous to the cuprates and promise to provide insight into the pairing mechanism in high-temperature superconducting oxides. The parent phase of doped superconducting films is ${\mathrm{NdNiO}}_{2}$, which is prepared by reducing ${3}^{+}$ Ni in ${\mathrm{NdNiO}}_{3}$ films. In this paper, we develop an ultrahigh vacuum reduction method using aluminum deposited on top of the ${3}^{+}$ nickelates and monitor the reduction process in real time through in situ crystal truncation rod measurements and diffraction x-ray absorption near edge spectroscopy measurements across the Ni $K$ edge. We establish a relation between Ni valence and the lattice constant of $\mathrm{NdNi}{\mathrm{O}}_{3\ensuremath{-}x}$ and show that the process can precisely control the oxygen content in the films. Finally, we extend the reduction process to quintuple square-planar nickelates.

Thermal upgrading of manganese ores prior to smelting

Ferromanganese smelting in electric arc furnaces is an energy-intensive process with corresponding CO2 emissions and environmental impacts. Upgrading the furnace charge can improve process efficiency and decrease electricity consumption. An oxide manganese ore, consisting mainly of pyrolusite, calcite and goethite, was thermally upgraded by calcination and solid-state reduction. During calcination of the ore at 900-1100?C, carbonates and hydroxides were decomposed and a considerable amount of oxygen was removed. The manganese content of the run-of-mine ore was increased from 39.86% to 47% after calcination. Carbothermic reduction of the ore at 1250?C resulted in almost all of the iron oxide and some of the manganese oxide passing into the metallic form. The results showed that a significant part of the endothermic reactions during the solid-state treatment of the ore can be carried out with low-cost fossil fuels. This leads to enrichment of the electric arc furnace charge, lower electricity consumption in the furnace, lower overall processing costs and a more efficient smelting process.

Solid-State Reduction of Vanadium Pentoxide by Hydrogen

Solid-State Reduction of Vanadium Pentoxide by Hydrogen

Engineered disorder in CO2 photocatalysis

Light harvesting, separation of charge carriers, and surface reactions are three fundamental steps that are essential for an efficient photocatalyst. Here we show that these steps in the TiO2 can be boosted simultaneously by disorder engineering. A solid-state reduction reaction between sodium and TiO2 forms a core-shell c-TiO2@a-TiO2-x(OH)y heterostructure, comprised of HO-Ti-[O]-Ti surface frustrated Lewis pairs (SFLPs) embedded in an amorphous shell surrounding a crystalline core, which enables a new genre of chemical reactivity. Specifically, these SFLPs heterolytically dissociate dihydrogen at room temperature to form charge-balancing protonated hydroxyl groups and hydrides at unsaturated titanium surface sites, which display high reactivity towards CO2 reduction. This crystalline-amorphous heterostructure also boosts light absorption, charge carrier separation and transfer to SFLPs, while prolonged carrier lifetimes and photothermal heat generation further enhance reactivity. The collective results of this study motivate a general approach for catalytically generating sustainable chemicals and fuels through engineered disorder in heterogeneous CO2 photocatalysts.