Hydrogen Reduction Method Research Articles

Anchoring ZnIn2S4 nanosheets on oxygen-vacancy NiMoOx nanorods for efficient photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution (PHE) from water splitting is one of the ideal choices for preparing renewable clean fuels in the future. Herein, a novel ZnIn2S4 (ZIS) nanosheets anchored oxygen vacancies NiMoOx(NMOx) nanorods (NMOx@ZIS) heterostructures were successfully prepared by high-temperature hydrogen reduction and subsequent solvothermal method. The as-prepared NMOx@ZIS-2.0 displays the highest PHE activity of 5.71 mmol·g−1·h−1 (with an optimized apparent quantum efficiency of 8.3 % at 420 nm) under visible light irradiation, which is approximately 11.2 times higher than pure ZIS. Moreover, the NMOx@ZIS composite exhibits excellent stability. Thanks to the construction of type II heterojunction between NMOx and ZIS, the recombination of photogenerated electron-hole (e--h+) pairs are effectively suppressed, thereby significantly improving the PHE activity of NMOx@ZIS composite. Besides, the presence of oxygen vacancies further inhibits the recombination of photogenerated e--h+ and provides more active reaction sites for H2 generation. The excellent photocatalytic activity and superior stability contributed to the application of NMOx@ZIS composite in the field of photocatalysis.

Synthesis and structure of compounds of the homological series TinO2n–1 obtained by reduction in a hydrogen environment

The paper considers one of the insufficiently explored methods for the synthesis of compounds of the homologous series TinO2n–1, in particular the method of hydrogen reduction. A series of samples (n = 2–8) were obtained from initial TiO2 powders of various chemical purities (99.0–99.99%) with modification with rutile in a wide range of temperatures and reduction times in a hydrogen environment. The influence of the purity of the initial samples, temperature and recovery time on the structure of the resulting compounds was established. Differences in the crystal structure of compounds of the homologous series TinO2n–1, as well as β- and λ-polymorphic modifications of Ti3O5, are shown. An approach to selecting the temperature and time of reduction of TiO2 powders to obtain a specific phase in compounds of the homologous series TinO2n–1 is substantiated.

Highly effective Pt-Pd/ZSM-22 catalysts prepared by the room temperature electron reduction method for the n-hexadecane hydroisomerization

The development of highly effective bifunctional catalysts for n-hexadecane hydroisomerization is still essential to produce second-generation biodiesel. Herein, a Pt-Pd/ZSM-22-G (abbreviated as Pt-Pd/Z22-G) bimetallic catalyst was prepared by employing a room temperature electron reduction (RTER) method with glow discharge as the electron source. As a contrast, a series of Pt/Z22-H, Pd/Z22-H and Pt-Pd/Z22-H catalysts were prepared by the conventional hydrogen reduction method. The Pt-Pd/Z22-G catalyst reveals more exposed metal sites, larger CMe/CH+ values and an enhanced distribution of Pt-Pd(111) facets compared with the Pt/Z22-H, Pd/Z22-H and Pt-Pd/Z22-H catalysts. These modifications are originated from the stronger electron interactions and the smaller metal nanoparticles because of the effects of highly energetic reducing electrons. The n-hexadecane hydroisomerization results show that the iso-hexadecane yield over the Pt-Pd/Z22-G catalyst is 82.9%, which is the highest among four investigated catalysts in this work. This phenomenon occurs because more exposed Pt-Pd(111) facets and larger CMe/CH+ ratios are beneficial for the adsorption and hydrogenation of iso-alkene intermediates at metal sites to increase the iso-alkanes yield based on density functional theory (DFT) calculations. Furthermore, the iso-alkanes yield over the Pt-Pd/Z22-G catalyst also keeps steady after long-term tests for 120 h because of the limited metal aggregation and carbon deposition.

CaH2-Assisted Molten Salt Synthesis of Zinc-Rich Intermetallic Compounds of RhZn13 and Pt3Zn10 for Catalytic Selective Hydrogenation Application

Zinc-included intermetallic compound catalysts of RhZn, PtZn, and PdZn with a molar ration of Zn/metal = 1/1, which are generally prepared using a hydrogen reduction approach, are known to show excellent catalytic performance in some selective hydrogenations of organic compounds. In this study, in order to reduce the incorporated mounts of the expensive noble metals, we attempted to prepare zinc-rich intermetallic compounds via a CaH2-assisted molten salt synthesis method with a stronger reduction capacity than the common hydrogen reduction method. X-ray diffraction results indicated the formation of RhZn13 and Pt3Zn10 in the samples prepared by the reduction of ZnO-supported metal precursors. In a hydrogenation reaction of p-nitrophenol to p-aminophenol, the ZnO-supported RhZn13 and Pt3Zn10 catalysts showed a higher selectivity than the RhZn/ZnO and PtZn/ZnO catalysts with the almost similar conversions. Thus, it was demonstrated that the zinc-rich intermetallic compounds of RhZn13 and Pt3Zn10 could be superior selective hydrogenation catalysts compared to the conventional intermetallic compound catalysts of RhZn and PtZn.

Effect of V-doping on structure and electrical conductivity of Magnéli phase Ti4O7

Magnéli phase Ti4O7 has been widely used in a range of electrochemistry disciplines due to its stable structure and excellent electrical conductivity. However, the conductivity advantages of Ti4O7 as a conductive addition are not readily visible, and the conductivity of Ti4O7 is significantly decreased by the presence of other titanium suboxide. The conductivity qualities of Ti4O7 can be improved by V. Studies on the impact of the amount of V on the structure and conductivity of Ti4O7, as well as the mechanism of V-enhanced conductivity of Ti4O7, are scarcely discernible. As a result, the effects of different V doping levels on the structure and conductivity of Ti4O7 were examined in this study, and when paired with carrier mobility calculation based on density functional theory (DFT) calculations, the mechanism behind V-enhanced Ti4O7 conductivity was discovered. Simple solvothermal and hydrogen reduction methods were used to prepare V-doped Ti4O7 at a variety of doping concentration. The conductivity of Ti4O7 improved with increasing V doping, however the presence of second phase (Ti1−xVx)2O3 decreased the conductivity of Ti4O7. This work is important for further understanding the optimal doping amount for V-enhanced Ti4O7 conductivity and the V-enhanced Ti4O7 conductivity behavior.

Recovery of Magnetic Particles from Wastewater Formed through the Treatment of New Polycrystalline Diamond Blanks

Cobalt’s pivotal role in global development, especially in lithium-ion batteries, entails driving increased demand and strengthening global trading networks. The production of different waste solutions in metallurgical operations requires the development of an environmentally friendly research strategy. The ultrasonic spray pyrolysis and hydrogen reduction method were chosen to produce nanosized magnetic powders from waste solution based on iron and cobalt obtained during the purification process of used polycrystalline diamond blanks. With specific objectives focused on investigating the impact of reaction temperature and residence time on the morphology, chemical composition, and crystal structure of synthesized nanosized cobalt powders, our research involved 15 experimental runs using two reactors with varying residence times (7.19 s and 23 s) and distinct precursors (A, B, and C). Aerosol droplets were reduced at 600 to 900 °C with a flow rate of 3 L/min of argon and hydrogen (1:2). Characterization via scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction revealed that higher temperatures influenced the spherical particle morphology. Altering cobalt concentration in the solution impacted the particle size, with higher concentrations yielding larger particles. A short residence time (7.9 s) at 900 °C proved optimal for cobalt submicron synthesis, producing spherical particles ranging from 191.1 nm to 1222 nm. This research addresses the environmental significance of recovering magnetic particles from waste solutions, contributing to sustainable nanomaterial applications.

Reduction of chengde vanadium titanium magnetite concentrate by microwave enhanced Ar–H2 atmosphere

In this study, a new method of microwave-enhanced hydrogen reduction was developed to carry out isothermal reduction experiments. The effects and mechanisms of different hydrogen volume fractions on the direct reduction behavior of a vanadium titanium magnetite concentrate (VTM) were investigated. The experimental results and theoretical analysis proved that combining the advantages of microwaves and hydrogen to reduce the VTM is feasible. The thermodynamics of the non-microwave field indicated that the hydrogen reduction of iron titanium oxides was more difficult than that of iron oxides and required a higher reaction temperature. Under microwave heating conditions, with an increase in hydrogen volume fraction, the metallization rate and reduction degree increased, the microscopic morphology developed into a porous sponge-like structure, the size of the internal pores increased, and the migration of metallic iron to the edges of the particles became obvious. When the hydrogen volume fractions exceeded 60%, the products did not contain TiO2, and the final products consisted of metallic iron containing a small amount of dissolved Ti. The reduction reaction was controlled by gas phase diffusion, and the average apparent activation energy was calculated to be 84.05 kJ/mol using a new kinetic model. Moreover, increased hydrogen volume fraction weakened the gas phase diffusion and was converted into internal diffusion.

A novel method for preparing ultrafine molybdenum‑rhenium alloy powders

To address the issues of large particle size and poor particle size uniformity in the traditional two-step hydrogen reduction method for preparing molybdenum‑rhenium alloy powders, this study innovatively employed glucose as the carbon source and successfully prepared ultrafine molybdenum‑rhenium alloy powders through wet-wet mixing, evaporative crystallization, calcination, carbothermal pre-reduction, and hydrogen deep reduction steps. The results demonstrate that when the C/(Mo + Re) molar ratio is 0.7, the powders synthesized through carbon‑hydrogen synergistic reduction exhibit a spherical shape, with particle sizes distributed in the sub-micrometer range and an average particle size of 173 nm. The phase composition of the reduction powders consists predominantly of molybdenum, rhenium and χ phases, with a uniform distribution of alloy elements. In contrast, the powders synthesized using the traditional two-step hydrogen reduction method exhibit irregular, porous and loosely-packed structures, with particle sizes in tens of microns range and slightly larger than those of the precursor. This method is highly suitable for preparing high-purity, ultrafine, and highly homogeneous binary alloy powders, like MoRe, MoW, WRe, ect.

Capillary assisted self-assembly and nascent hydrogen reduction of graphene oxide on Al: Formation of C–O–Al bonds under mild condition

Graphene has been recognized as reinforcement and/or protective coating for metal materials due to its unique electronic, mechanical properties and chemical inertness. Challenges of graphene agglomeration and weak graphene/metal interfacial bonding still exist during preparation. Here we report a novel method combining capillary-assisted self-assembly with nascent hydrogen reduction technique to one step coat Al foil with layered-stacking graphene. Al foil constructed slit is filled with graphene oxide (GO) suspensions and the generation of nascent hydrogen occurs at the GO/Al interface. The capillary force drives the GO flakes to layer-by-layer assemble on Al foil, as well as increases the reduction depth of GO. X-ray photoelectron spectroscopy (XPS) reveals that the reduced GO (rGO) binds with Al is not just through van der Waals forces, but with a strong interaction of developing C–O–Al bonds. The hydroxyl groups on GO plays an essential role in the formation of such C–O–Al configuration. Al foil coated with rGO through this capillary-assisted self-assembly with nascent hydrogen reduction method show good corrosion resistance compared to the pristine Al and directly drop-casted GO on Al. The proposed method can be readily applied to the fabrication of graphene/metal composites with improved interfaces.

Hydrogen reduction process for zinc-bearing dust treatment: Reduction kinetic mechanism and microstructure transformations in a novel and environmentally friendly metallurgical technique

The iron and steel sector generates 80 million tons of zinc-containing dust annually, traditionally treated using carbon-based pyrometallurgical processes, which have significant drawbacks, including large carbon emissions, high energy consumption, and low production value. To address the above issues, a green hydrogen reduction method was developed for zinc-bearing dust treatment. This study examined the thermodynamics, reduction kinetics, and phase transformation during the process, revealing that at 800 °C, the hydrogen partial pressure for zinc oxide reduction is only 45.56 %. The direct reduction of zinc-containing dust pellets with hydrogen reveals that the limiting step of iron oxide and zinc reductions both are interfacial chemical reaction control at the reduction temperature of 800–950 °C, with an apparent activation energy of 16.42 kJ/mol and 71.39 kJ/mol. The kinetic mechanism indicates that reducing iron and zinc oxides is more accessible in a hydrogen reduction system, with lower apparent activation energies than carbothermal reduction. Consequently, hydrogen reduction offers a more efficient and environmentally friendly solution for treating zinc-bearing dust.

Development of hydrogen reduction method for La–Fe–Si materials from oxalate precursors

ABSTRACT Hydrogen reduction was used to synthesise LaFeSi-based materials from lanthanum, cerium, iron oxalates, and silicon dioxide. The process involved the pre-reduction of the precursor powder mixture at 650°C under N2 for 1 h, followed by a full reduction under H2 for 2 h at 900°C. The predominant phases in the synthesised materials were a-Fe, lanthanum, cerium, and silicon oxides. A decrease in the La/Ce ratio in the main composition resulted in an increase in the a-Fe phase. The rest of the non-oxidized materials showed an Fm-3 m structure. Both XRD and EDS analyses indicated the presence of metal/oxide composite structure in the synthesised materials. The oxide morphology observed in SEM images exhibited a porous media. The room temperature VSM analysis showed that x = 0.3 product had the highest coercivity as 26 Oe and the lowest saturation magnetisation as 106.3 emu/g.

Preparing and Wear-Resisting Property of Al2O3/Cu Composite Material Enhanced Using Novel In Situ Generated Al2O3 Nanoparticles.

Al2O3/Cu composite material (ACCM) are highly suitable for various advanced applications owing to its excellent properties. In the present work, a combination of the solution combustion synthesis and hydrogen reduction method was first employed to prepare Al2O3/Cu composite powder (ACCP), and subsequently ACCM was prepared by employing spark plasma sintering (SPS) technique. The effect of Al2O3 contents and SPS temperatures on the properties (relative density, hardness, friction coefficient, and electrical conductivity, et al.) of ACCM were investigated in detail. The results indicated that ACCM was very dense, and microstructure was consisted of fine Al2O3 particles evenly distributed in the Cu matrix. With the increase of SPS temperature, the relative density and hardness of ACCM had first increased and then decreased. At 775 °C, the relative density and hardness had attained the maximum values of 98.19% and 121.4 HV, respectively. With the increase of Al2O3 content, although the relative density of ACCM had gradually decreased, nevertheless, its friction coefficient had increased. Moreover, with the increase of Al2O3 contents, the hardness of ACCM first increased and then decreased, and reached the maximum value (121.4 HV) with 3 wt.% addition. On the contrary, the wear rate of ACCM had first decreased and then increased with the increase of Al2O3 contents, and attained the minimum (2.32 × 10-5 mm3/(N.m)) with 3 wt.% addition.

Enhancement of 15% calcium oxide doped nano zero-valent iron on arsenic removal from high-arsenic acid wastewater.

Nano zero-valent iron (nZVI) has a great potential for arsenic removal, but it would form aggregates easily and consume largely by H+ in the strongly acidic solution. In this work, 15%CaO doped with nZVI (15%CaO-nZVI) was successfully synthesized from a simplified ball milling mixture combined with a hydrogen reduction method, which had a high adsorption capacity for As(V) removal from high-arsenic acid wastewater. More than 97% As(V) was removed by 15%CaO-nZVI under the optimum reaction conditions of pH 1.34, initial As(V) concentration 16.21g/L, and molar ratio of Fe/As (nFe/nAs) 2.5:1. The effluent pH solution was weakly acidic 6.72, and the secondary arsenic removal treatment reduced the solid waste and improved arsenic grade in slag from the mass fraction of 20.02% to 29.07%. Multiple mechanisms including Ca2+ enhanced effect, adsorption, reduction, and co-precipitation coexisted for As(V) removal from high-arsenic acid wastewater. Doping of CaO might lead to improving cracking channels which was benefit for electronic transmission and the confusion of atomic distribution. The in situ weak alkaline environment generated on the surface of 15%CaO-nZVI would increase the content of γ-Fe2O3/Fe3O4, which was in favor for As(V) adsorption. In addition, H+ in the strongly acidic solution could accelerate corrosion of 15%CaO-nZVI and abundant fresh and reactive iron oxides continuously generated, which would provide plenty specific reactive site and fast charge transfer and ionic mobility for arsenic removal.

3 nm-Wide WO3–x Nanorods with Abundant Oxygen Vacancies as Substrates for High-Sensitivity SERS Detection

Oxygen vacancy (Vo) engineering is a powerful tool to improve semiconductor metal oxide-based surface-enhanced Raman scattering (SERS) activity due to the enriched surface states of substrates. However, the current energy-consuming high-temperature hydrogen reduction methods of introducing Vo and the poor sensitivity impede practical applications of semiconductor SERS. In this work, a facile solvothermal method was developed to prepare ultrafine WO3–x nanorods (∼3 nm width) for high-performance SERS substrates. The lowest detection limit of the rhodamine 6G (R6G) molecule on the Vo substrate can be as low as 10–10 mol/L and exceeds that of unmodified WO3 by more than two orders of magnitude. Experimental and calculated results suggest that the Vo-induced localized surface plasmon resonance (LSPR), diverse vibronic coupling, and enhanced charge transfer synergistically account for this outstanding activity. These findings can provide insights into the rational design of oxygen vacancy-tailored semiconductor SERS substrates.

Synergetic effect of the interface electric field and the plasmon electromagnetic field in Au-Ag alloy mediated Z-type heterostructure for photocatalytic hydrogen production and CO2 reduction

The challenge of synergistically optimizing different mechanisms limits the further improvement of plasmon-mediated photocatalytic activities. In this work, the CdS/Au-Ag/B-TiO2 photocatalyst, combining a heterojunction structure with localized surface plasmon resonance (LSPR), is prepared by a high-temperature hydrogen reduction and hot solvent method. The novel synergistic interaction at the interface between the electric field and the plasmon electromagnetic field drives effective charge separation with improved photocatalytic efficiency. The Cd3Ti2 catalyst exhibits the highest photocatalytic activity, and the H2 generation efficiency under the full solar spectrum is 15.97 mmol⋅h−1⋅g−1 with good stability as high as 81.3% in 24 h cycles. The CH4 and CO precipitation performances are achieved at 14.2 μmol⋅h−1⋅g−1 and 113.9 μmol⋅h−1⋅g−1, respectively, in the CO2RR process. The design of the synergistic mechanism of the dual electric field offers an important development in the field of plasma-mediated photoredox catalysis.

Spherical Ni/Ni3Se2 Heterostructure for Efficient Electrochemical Oxidation Reactions

AbstractA Ni/Ni3Se2 metal‐semiconductor heterojunction catalyst with a sphere structure was prepared by a hydrothermal and hydrogen reduction method. The results showed that the heterostructure Ni/Ni3Se2 exhibits better performance than Ni3Se2 and Ni counterparts for electrochemical oxidation reactions. During electrocatalytic water oxidation, the overpotential is 340 mV to reach a catalytic current density of 10 mA cm−2 in 1.0 M KOH solution. The heterogeneous interface formed between the metal Ni and Ni3Se2 in the Ni/Ni3Se2 catalyst can accelerate the electron transfer in the electrochemical oxidation process. Moreover, the as‐prepared material is also applied for sulfonamide degradation, with the aid from hydroxyl radicals generated during water oxidation. This application is meaningful since the product from water oxidation is not desired in hydrogen production from water electrolysis. The material with heterojunctions delivered degradation efficiency up to 80% of sulfonamide antibiotics within 2 h. Therefore, the Ni/Ni3Se2 material might have application prospects in electrochemical sustainability research.

Anchoring highly distributed Pt species over oxidized graphitic carbon nitride for photocatalytic hydrogen evolution: The effect of reducing agents

Platinum (Pt) as a cocatalyst over graphitic carbon nitride (g-C3N4) is the main active site in the hydrogen evolution reaction (HER). Therefore, controlling the properties of Pt is significant to achieve a high H2 production yield in which the reduction step of the Pt precursor is an important factor. In this study, we prepared Pt-loaded chemically oxidized g-C3N4 photocatalysts for photocatalytic hydrogen evolution using different Pt deposition methods-chemical reduction with hydrazine, hydrogen reduction, and photoreduction. The hydrogen evolution rate of the chemically oxidized Pt/g-C3N4 photocatalysts prepared via hydrogen reduction (1152.8 µmol g-1h−1) was the highest compared to those prepared via chemical reduction (409.9 µmol g-1h−1) and photoreduction (583.7 µmol g-1h−1). The hydrogen reduction method with a fine reducing ability could achieve a uniform distribution of Pt nanoparticles anchored onto the chemically oxidized g-C3N4 nanosheets while maintaining homogeneity between the Pt precursor – reducing agent – g-C3N4. Furthermore, during hydrogen reduction, the greatest ─C═O content and lowest concentrations of ─COOH and ─COH groups on the g-C3N4 surface resulted in an extremely high Pt2+/Pt0 ratio, a strong electronic Pt–g-C3N4 interaction, and the highest charge transfer efficiency, enhancing the hydrogen evolution rate.

Ternary alloy incorporated Janus hydrogel photothermal film for desalination

Here, we developed a ternary alloy (Cu 0.4 W 0.6 /Ni 17 W 3 ) based Janus hydrogel photothermal film for solar-driven water evaporation. We first prepared the copper-doped nickel tungstate, then obtained the Cu 0.4 W 0.6 /Ni 17 W 3 using the hydrogen reduction method, and applied it as the photothermal conversion material for the upper layer of the Janus photothermal film. The Cu 0.4 W 0.6 /Ni 17 W 3 had low cost, perfect solar spectrum matching, and excellent thermal stability. A composite hydrogel composed of gelatin and agar was used to prepare the Janus photothermal film. The Janus photothermal film showed an excellent water evaporation rate of 1.72 kg m -2 h −1 and a high light-to-heat conversion efficiency (η) of 98% under one-sun irradiation. Besides, Janus-1 possessed excellent desalination performance.

Dysprosium regulated platinum particles as a bimetallic alloy catalyst for oxygen reduction reaction

Pt rare earth compounds have recently been investigated as potential substitutes. In this study, the hydrogen reduction method was used to prepare the Pt-Dy bimetallic catalyst, and a number of characterizations were conducted for structure and morphological research. The high resolution-transmission electron microscopy (HR-TEM) and X-ray diffraction results show that Pt-Dy composite material exists in the form of various alloys and has a clear spherical shape. The majority of the metals in the composite catalyst appear in the zero valent state, and the binding energy of Pt shifts significantly, according to an X-ray photoelectron spectroscopy measurement. Impressively, Pt-Dy alloy produces excellent mass activity of 594 A/g compared to commercial Pt/C catalyst (162.8 A/g) for oxygen reduction process. Furthermore, after an accelerated durability test, the catalytic activity loss for Pt-Dy alloy catalyst reaches 20% while commercial Pt/C reduces 56%.

Nanoarchitectonics of Ni/CeO2 Catalysts: The Effect of Pretreatment on the Low-Temperature Steam Reforming of Glycerol.

CeO2 nanosphere-supported nickel catalysts were prepared by the wetness impregnation method and employed for hydrogen production from glycerol steam reforming. The dried catalyst precursors were either reduced by H2 after thermal calcination or reduced by H2 directly without calcination. The catalysts that were reduced by H2 without calcination achieved a 95% glycerol conversion at a reaction temperature of only 475 °C, and the catalytic stability was up to 35 h. However, the reaction temperature required of catalysts reduced by H2 with calcination was 500 °C, and the catalysts was rapidly inactivated after 25 h of reaction. A series of physicochemical characterization revealed that direct H2 reduction without calcination enhanced the concentration of oxygen vacancies. Thus, the nickel dispersion was improved, the nickel nanoparticle size was reduced, and the reduction of nickel was increased. Moreover, the high concentration of oxygen vacancy not only contributed to the increase of H2 yield, but also effectively reduced the amount of carbon deposition. The increased active nickel surface area and oxygen vacancies synergistically resulted in the superior catalytic performance for the catalyst that was directly reduced by H2 without calcination. The simple, direct hydrogen reduction method remarkably boosts catalytic performance. This strategy can be extended to other supports with redox properties and applied to heterogeneous catalytic reactions involving resistance to sintering and carbon deposition.