Mixture Of Na2CO3 Research Articles

Silver recovery into lead bullion from a lead concentrate by direct reduction with Na2CO3 and SiC reagents

ABSTRACT Silver has been recovered in lead bullion from a lead concentrate throughout a direct reduction process. The lead concentrate was obtained from a plant that processes polymetallic minerals located in the central mining area of Mexico. The direct reduction process has been tested through mixtures of Na2CO3 and SiC that were put in contact with the lead concentrate at 1000 °C for 60 min to produce lead bullion containing silver and slag. The produced lead bullion containing silver and the slag after direct reduction trials showed that it is possible to recover about 90% of lead and 86.5% of silver into the lead bullion, leading to a low silver content in the slag phase (<0.2 wt.%). The slag was constituted mainly by sodium silicate compounds such as Na2SiO3, Na4SiO4, and Na2Si2O5, when 50 wt. % of Na2CO3 and 10 wt. % of SiC regarding the initial charge of the lead concentrate was used. The proposed process has been assisted thermodynamically by the software FactSage 7.6, which allowed us to predict the main expected compounds and understand the process mechanism for silver recovery into a lead bullion using Na2CO3 and SiC reagents.

Na3Sc(PO4)2: Thermal behaviors, distorted β-K2SO4-type structure and dielectric properties

The Na3Sc(PO4)2 (NSPO) compound was obtained by solid-state synthesis method and has a new type of distorted β-K2SO4 (arcanite) crystal structure that was refined based on powder XRD data in the space group (SG) P21/c, with unit cell parameters: a = 11.5533(1) Å, b = 5.31759(5) Å, c = 16.7650(2) Å, β = 97.6439(6)°. The NSPO is a metastable phase with an optimal synthesis temperature range between 1173 and 1233 K. When a mixture of Na2CO3, NH4H2PO4 and Sc2O3 is annealed below this temperature range, the NaSICON-type compound and Na-polyphosphates is formed. However, annealing above T∼1245 K leads to the decomposition onset into the NaSICON-type compound (Na3Sc2(PO4)3), Na3PO4 and terminates at T∼1289 K. NSPO phase is dielectric with σbulk = 4.4 × 10−7 S/cm at 300 K. Increasing the temperature from 300 to 1000 K leads to an increase in σbulk by four orders (σbulk = 5.6 × 10−3 S/cm at 1000 K).

Transformative strategies for heavy metals extraction: Ionic liquid-boosted fizzy capsule for distributive solid-phase microextraction in aquatic environments

Within this work, an innovative ionic liquid-coated sulphonyl silanized graphene oxide-supported fizzy capsule-enhanced ionic liquid distributive solid-phase micro-extraction (MGO@SO3H-IL-DSPM) was successfully prepared for enriching and extracting lead [Pb(II)], cadmium [Cd(II)], and cobalt [Co(II)] ions from water samples. The MGO@SO3H hybrid was investigated using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), Zeta potential and surface area. Exploration and optimization were conducted on various parameters including solution pH, dosages of extractant, volume of ionic liquid, and the type and concentration of eluent. The optimized experimental conditions for achieving high extraction efficiencies of the targeted metals were determined as follows: a mixture of Na2CO3 and NaH2PO4 (0.12 g) each, at a 1:1 M ratio); utilization of 0.03 g of MGO@SO3H nanocomposites; addition of 10 μL of ionic liquid as the extractant; pH adjustment to approximately 5 for Pb(II), and 4.18 for both Co(II) and Cd(II); and elution using HNO3 as the eluent (at a concentration of 1.5 M, with a volume of 3 ml). Under the ideal circumstances, the extraction yield efficiencies of the target metal ions in four authentic water samples were in the range (96.09 % − 100 %) for Cd(II), (99.99 % − 102 %) for Pb(II), and (99.99 % − 103 %) for Co(II), the RSDs were lower than 1.7 %. The content of Cd(II), Pb(II), and Co(II) ions in four actual samples of water were determined within the range of 1.25 – 3.75 μg/L, 6 – 15 μg/L, and 29.15 – 70 μg/L, respectively.

Structure of Na Species in Promoted CaO‐Based Sorbents and Their Effect on the Rate and Extent of the CO2 Uptake

AbstractTo advance CaO‐based CO2 sorbents it is crucial to understand how their structural parameters control the cyclic CO2 uptake. Here, CaO‐based sorbents with varying ratios of Na2CO3:CaCO3 are synthesized via mechanochemical activation of a mixture of Na2CO3 and CaCO3 to investigate the effect of sodium species on the structure, morphology, carbonation rate and cyclic CO2 uptake of the CO2 sorbents. The addition of Na2CO3 in the range of 0.1–0.2 mol% improves the CO2 uptake by up to 80% after 10 cycles when compared to ball‐milled bare CaCO3, while for Na2CO3 loadings &gt;0.3 mol% the cyclic CO2 uptake decreases by more than 40%. Energy dispersive X‐ray spectroscopy (EDX), transmission electron microscopy, X‐ray absorption spectroscopy (XAS), and 23Na MAS NMR, reveal that in sorbents with Na2CO3 contents &lt;0.3 mol% Na exists in highly distributed, noncrystalline [Na2Ca(CO3)2] units. These species stabilize the surface area of the sorbent in pores of diameters &gt;100 nm, and enhance the diffusion of CO2 through CaCO3. For Na2CO3 contents &gt;0.3 mol%, the accelerated deactivation of the sorbents via sintering is related to the formation of crystalline Na2Ca(CO3)2 and the high mobility of Na.

Synthesis of Fe-deficient eudialyte analogues: Relationships between the composition of the reaction system and crystal-chemical features of the products

AbstractEudialyte-related compounds have been synthesised hydrothermally at T = 600°C and P = 2 kbar from a stoichiometric mixture of Na2CO3, CaO, Fe2O3, ZrOCl2 and SiO2 using the Na:Ca:Fe:Zr:Si ratios corresponding to the eudialyte end-member Na15Ca6Fe3Zr3Si(Si25O73)(OH)Cl2⋅H2O, in the presence of 1 M aqueous solutions of NaCl and NaF. The synthesis was carried out in platinum ampoules over 10 days. Natural raslakite (a Ca-deficient member of the eudialyte group) was used as a seed and added in amounts corresponding to 2 wt.% of the whole charge. The products were characterised by powder X-ray diffraction, IR and Raman spectroscopy, morphological features, and electron probe microanalyses. In experiments with NaCl, almost pure eudialyte-type compounds were obtained. Synthesis in the presence of a NaF solution resulted in the formation of a F-dominant eudialyte-type compound related to raslakite as the main product and aegirine, vlasovite and lalondeite as by-products. All synthesised eudialyte-type compounds are Zr-rich and Fe-deficient, similar to eudialyte-group minerals from hyperagpaitic rocks related to foyaites. The increased NaCl contents in the reaction system results in increased Ca content in the synthesised eudialyte-related compounds. The crystal-chemical formulae of the synthesised eudialyte-type compounds are derived based on general regularities established earlier for eudialyte-group minerals.

Effect of atomic substitution on the sodium manganese ferrite thermochemical cycle for hydrogen production

This work presents the effect of atomic substitution on the MnFe2O4–Na2CO3 thermochemical cycle for H2 production. The non-oxidative decarbonation/carbonation reaction of the MnFe2O4–Na2CO3 mixture is investigated as the starting reference. Repeated cycling results in a 30% loss of reversibility due to an overall reduction of the reactive interfaces. The substitution of Na2CO3 for Li2CO3 decreases the decarbonation onset temperature by about 100 °C, but almost no reversibility is observed during the cycles due to the irreversible Li+ intercalation. The effect of partial Mn substitution for Ca, Ni, and Zn is presented. The 5% Zn mixture shows the best decarbonation/carbonation reversibility and is tested for H2 production together with MnFe2O4–Na2CO3. The reference mixture produces more H2 during the first cycle (≈1.1 vs. 0.7 mmol/g), but its production drastically drops by two orders of magnitude upon cycling and becomes negligible after 5 cycles. By contrast, the Zn-doped mixture exhibits a stable H2 production of 0.22 mmol/g with no decreasing trend observed from cycle 2 to cycle 5. As result, in the fifth cycle, the Zn-doped mixture produces 23 times more H2 than MnFe2O4–Na2CO3. Thermogravimetry and X-ray diffraction confirm that doping with Zn significantly improves the regeneration of the reactants.

Alkaline Salt Tolerance of the Biomass Plant Arundo donax

Soil alkalinization and salinization have increased worldwide due to extreme and/or prolonged drought periods as well as insufficient irrigation. Since crops generally react to soil salinity and high pH with decreased yield, the cultivation of tolerant biomass plants represents a reasonable alternative. Thus, we aimed to characterize the tolerance of the biomass plant Arundo donax to alkaline salt stress, induced by irrigation water containing NaHCO3 and Na2CO3 mixture (1:1) at 80 mM and 200 mM of final concentration and pH 10. In terms of physiological parameters such as transpiration, chlorophyll content, photosystem II quantum efficiency, relative water content, and water saturation, the plants were resistant to the stress treatment. The negative impact on the water regime was only measured at 200 mM salt. The K/Na ratio decreased in parallel with Na accumulation. Plants also accumulated Zn, whereas a decrease in the concentration of most other elements (Ca, Cu, K, Mg, Ni, S, Si, and Sr) was detected. Antioxidative defence directed by multiple symplastic enzymes contributed to the high physiological tolerance to the applied stress. In conclusion, the cultivation of Arundo donax as a biomass crop appears to be a feasible alternative in areas affected by salinity or alkaline salt accumulation.

Efficient adsorption and porous features from activated carbon felts activated by the eutectic of Na2CO3 and K2CO3 with vapor

In this work, a cost-effective eutectic mixture of Na2CO3 and K2CO3 was developed for preparing PAN-based activated carbon fibers (ACFs). Rapid activation (15 min) was achieved when using pre-oxygenated PAN felts as carbon source and a low amount (mass fraction of 0.5%) of the eutectic and water vapor as synergistic activating agents. The prepared ACFs exhibited high specific surface area (2175.0 m2/g), excellent benzene adsorption capacity (704.5 mg/g), and iodine adsorption capacity (2231.0 mg/g). Hierarchical structure of micropores and mesopores provided sites for gas adsorption. This study is expected to realize the industrial production of ACFs at a low cost.

Buffer effect of MgO on Na2SO3 to stabilize S(IV) for the enhancement in simultaneous absorption of NOx and SO2 from non-ferrous smelting gas.

Oxidation-reduction-absorption based on sulfite is a promising process for simultaneous removal of NOx and SO2. However, excessive oxidation of sulfite and competitive absorption between NOx and SO2 limit its application. A matching strategy between antioxidants and alkaline agents has been proposed to solve these problems and enhance the absorption process. The comparison results of inhibitors showed that hydroquinone exhibited long-term high-efficiency inhibition of S(IV) (SO32-/HSO3-) oxidation. The comparison of alkaline agents showed that the Na2SO3 solution with heterogeneous mixture of MgO and hydroquinone exhibited better absorption performance than that with other combinations. The absorption amounts of NOx in 0.15mol/L Na2SO3 50mL solution added 0.1% hydroquinone (HQ) with 0.09mol/L MgO were 2.24mmol, which improved 5 times than that without additives. In addition, studies on the influence of pH showed that the pH of MgO mixture could be stabilized at 9-10 for a long time, while the pH of Na2CO3 mixture decreased faster. Further studies suggested that the hydration of MgO resulted in the solution with MgO keeping high pH. This is also the main reason why the combination of MgO and hydroquinone is superior to the combination of Na2CO3 and hydroquinone in desulfurization and denitration performance.

Analysis of the Leaching Stage Effect on the Vanadium Extraction from Technogenic Raw Materials

As a result of titanomagnetite iron ore processing, technogenic waste is formed in the form of vanadium-containing slags. The industrial processing of these slags is important to improve the environmental situation in industrial regions and expand vanadium raw material base. The study purpose was the vanadium extraction from slags of titanomagnetite ore processing (ITmk3 process slag and JSC “EVRAZ NTMK” slag) in the soluble vanadate form. Research tasks: hydrometallurgical vanadium extraction from slags of different chemical composition using soda technology; determination of the leaching mode effect (temperature and duration) on the vanadium extraction degree. Experimental samples in the form of slag and soda Na2CO3 mixture were processed to oxidative roasting and subsequent water leaching at different temperatures from 50 °C to 80 °C for 1, 2 and 3 hours. In the resulting solutions the vanadium content was determined with X-ray fluorescence spectroscopy (XRF). Analysis of the research results showed that the slag chemical composition and the water leaching conditions had a significant effect on vanadium extraction degree. The vanadium extraction degree from the JSC “EVRAZ NTMK” slag was 2 – 2.5 times higher than from the ITmk3 process slag after applying the same leaching modes. The highest degree of vanadium extraction was obtained after leaching at a temperature of 80 °C for 3 hours. These leaching modes increased the vanadium extraction degree from the JSC “EVRAZ NTMK” slag to 65 – 87%, and from the ITmk3 process slag to 31 – 33%.

Lead Recovery from a Lead Concentrate throughout Direct Smelting Reduction Process with Mixtures of Na2CO3 and SiC to 1000 °C

Lead was recovered through a direct smelting reduction route from a lead concentrate by using mixtures of Na2CO3 and SiC to 1000 °C. The lead concentrate was obtained from the mining State of Zacatecas, México by traditional mineral processing and froth flotation. The experimental trials showed that 86 wt.% of lead with a purity up to 97% can be recovered from the lead concentrate by a single step reduction process when 40 wt.% Na2CO3 and 0.4 g SiC were used in the initial charge. The process was modeled in the thermodynamic software FactSage 7.3 to evaluate the effect of adding different amounts of Na2CO3 on the lead recovery rates while holding constant the SiC amount and temperature. The stability phase diagram obtained showed that an addition of 34 wt.% Na2CO3 was enough to reach the highest lead recovery. It was observed that the interaction of Na2CO3 and SiC at a high temperature promotes the formation of C and Na2O, and SiO2, respectively, where the Na2O partially bonds with silica and sulfur forming Na2S and sodium silicates which may decrease the SO2 emissions and increase the weather degradation of the slag. The PbS was mainly reduced by the produced C and CO formed by the interaction between Na2CO3 and SiC at 1000 °C. The predicted results reasonably match with those obtained experimentally in the lead recovery rates and compounds formation.

High temperature X-ray diffraction study of the formation of Na2Ti3O7 from a mixture of sodium carbonate and titanium oxide

Na2Ti3O7 has attracted much attention in the field of anode materials for Na-ion batteries thanks to its non-toxicity and very low working potential of 0.3 V vs Na0/Na+. Building a clearer picture of its formation from cheap Na2CO3 and TiO2 starting materials is therefore of obvious interest. Here, we report new insights from an in-situ high temperature X-ray diffraction study conducted from room temperature to 800 °C, complemented by ex-situ characterizations. We were thereby able to position the previously reported Na4Ti5O12 and Na2Ti6O13 intermediate phases in a reaction scheme involving three successive steps and temperature ranges. Shifts and/or broadening of a subset of the Na2Ti6O13 reflections suggested a combination of intra-layer disorder with the well-established ordering of successive layers. This in-situ study was carried out on reproducible mixtures of Na2CO3 and TiO2 in 1:3 molar ratio prepared by spray-drying of mixed aqueous suspensions. Single-phase Na2Ti3O7 was obtained after only 8 h at 800 °C in air, instead of a minimum of 20 h for a conventional solid-state route using the same precursors. Microstructure analysis revealed ~ 15 µm diameter granules made up from rectangular rods of a few-µm length presenting electrochemical properties in line with expectations. In the absence of grinding or formation of intimate composites with conductive carbon, the specific capacity of 137 mAh/g at C/5 decreased at higher rates.

Process for Enhancing the Valuable Metal Recovery from "Electric Arc Furnace" (EAF) Slags

Given the current depletion of the world's natural resources, the strong demand and the induced future deposit of primary mineral resources carrying metals (such as molybdenum, vanadium and chromium), one of the solution to this problem is the recycling of metals from by-products (such as steel slags) containing them. Steel slags are major by-products produced by the steel industry. Although they are considered as industrial waste that may cause public and environmental concerns, slags represent an important potential economic resource because they often contain significant amounts of valuable "Strategic Metals" (SMs). In order to minimize energy costs, environmental impacts and meet the metals demand for new high technologies, it will be more and more necessary to use cleaner and more economical technologies to recover these metals from slags. In this study, steel slags, generated from electrical arc furnace and provided by the Industeel France ArcelorMittal Company located in Châteauneuf (France), were studied. The chemical and mineralogical characterization results show that the investigated slags contain approximately 20–22% Fe, 3–4% Cr, 1 500 ppm V and are constituted of the following main crystalline phases: larnite (Ca2SiO4), magnetite (Fe3O4), wustite (FeO) and chromite (FeCr2O4). Slag samples underwent different treatment steps before leaching (magnetic separation, grinding at d ≤ 25 μm and roasting). Various alkaline reagents (NaOH, KOH, Na2CO3 and K2CO3) have been studied with a slag/reagent weight ratio of 1, sufficiently high to provide an excess of alkaline reagent and allows the complete modification of the metal species able to be modified with these reagents at different co-grinding residence times. Three temperatures (400, 600 and 800 °C) were tested. The results show that the Cr leaching rate reaches 97.5% for one hour of the slag co-grinding with a NaOH and Na2CO3 mixture followed by roasting at 800 °C, while the V maximum leaching rate of 62.5% of vanadium is obtained after three hours of slag co-grinding with NaOH and Na2CO3 and roasted at 600 °C. The Mo leaching rate, meanwhile, reaches 95.8% using KOH for one hour of co-grinding the slag followed by roasting at 600 °C.

Efficient separation of fluoride and graphite carbon in spent cathode carbon from aluminum electrolysis by mechanical activation assisted alkali fusion treatment

Spent cathode carbon (SCC) is the largest and most inevitable hazardous solid waste continuously discharged from the aluminum electrolysis industry. In this study, mechanical activation was used to assist alkali fusion treatment in dissociating toxic substances and recovering graphite carbon from SCC. The effect of mechanical activation (i.e., milling speed, ball-to-material mass ratio, and milling time) on the alkali fusion treatment was investigated. Its effect on the physicochemical properties of SCC–Na2CO3 mixtures was also analyzed through particle size distribution, Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy, X–ray diffraction and thermogravimetric analysis–differential scanning calorimetry. Results showed that mechanical activation enhanced the alkali fusion treatment by improving the physical separation of fluoride, the mixing uniformity and reaction contact area of SCC and Na2CO3, and promoting the conversion of Na2CO3 to Na2O. The formation of agglomerates was the main reason that the carbon content of recovered graphite carbon and the fluoride ion leaching rate increased initially then decreased with the increment in mechanical activation conditions. Under optimal mechanical activation conditions, the carbon content of recovered graphite carbon and the fluoride ion leaching rate increased from 89.35% and 76.50% (non-activated sample) to 93.93% and 95.02%, respectively, indicating that mechanical activation assisted alkali fusion treatment effectively enhanced the separation efficiency of fluoride and graphite carbon. In addition, thermodynamic analysis of the alkali fusion treatment and characterization of recovered graphite carbon (under the optimal mechanical activation conditions) were performed. Results demonstrated that the simultaneous conversion of multiple fluorides (i.e., Na3AlF6 and CaF2) and oxidative decomposition of cyanide in SCC can be achieved via mechanical activation assisted alkali fusion treatment. These findings indicate that mechanical activation–assisted alkali fusion treatment is a promising method for the detoxification and utilization of SCC.

Innovative improvement of sintered ceramic electrolytes by salt infiltration

Previously sintered (1500 °C, 4 h) dense pellets of Ce0.9Gd0.1O1.95 (GDC) were covered and heat treated with eutectic mixtures of Na2CO3 and Li2CO3 (NLC), and their electrical performance was assessed against pure GDC and chemically synthesized GDC + NLC. Microstructural analysis of NLC impregnated samples confirmed slight migration of the molten phase to the interior of the GDC pellets via grain boundaries, resulting in a significant improvement of the grain boundary conductivity, increasing with duration of heat treatment (0.5–2 h) and temperature (600–800 °C range). The observed total conductivity exceeded in almost 20% the corresponding values obtained for standard GDC samples. Cells tested before and after direct current polarization (0.5 V, 500 °C) showed the same electrical performance, discarding the possibility of parallel contributions of salt ions to the total conductivity. Grain boundary engineering using salt infiltration is an effective tool to improve the electrical performance of ceramic electrolytes.

Determination of the iron oxide content in bauxite: comparing ICP-OES with UV–VIS and volumetric analysis

This study presents the results of the iron oxide content determination in bauxite by means of inductively coupled plasma optical emission spectrometry (ICP-OES), volumetry, and UV–VIS spectrophotometry. Nine certified bauxite reference samples with Fe2O3 content from 7.14 to 28.20% were analyzed. Two methods of bauxite sample preparation were applied: melting with a mixture of Na2CO3:Na2B4O7 (3:1) and dissolving with a combination of acids (HCl, HNO3, and H2SO4). The recovery value for all the methods used in relation to the certified values was in the range from 92.41% to 113.87%. By using statistical tests, it has been confirmed that the results of ICP-OES analysis generally agree with other methods, which supports its adoption as an alternative for Fe2O3 determination in bauxite. Due to a shorter preparation time and complete dissolution, it is recommended to prepare the samples by melting.

Influence of Surface Modification of MK-40 Membrane with Polyaniline on Scale Formation under Electrodialysis.

A comprehensive study of the polyaniline influence on mineral scaling on the surface of the heterogeneous MK-40 sulfocationite membrane under electrodialysis has been conducted. Current-voltage curves and chronopotentiograms have been obtained and analyzed for the pristine MK-40 membrane and the MK-40 membrane which is surface-modified by polyaniline. The study of the electrochemical behavior of membranes has been accompanied by the simultaneous control of the pH of the solution outcoming from the desalination compartment. The mixture of Na2CO3, KCl, CaCl2, and MgCl2 is used as a model salt solution. Two limiting states are observed on the current-voltage curve of the surface-modified membrane. There is the first pseudo-limiting state in the range of small values of the potential drop. The second limiting current is comparable with that of the limiting current for the pristine membrane. It is shown that chronopotentiometry cannot be used as a self-sufficient method for membrane scaling identification on the surface-modified membrane at high currents. A mineral scale on the surfaces of the studied membranes has been found by scanning electron microscopy. The amount of precipitate is higher in the case of the surface-modified membrane compared with the pristine one.

Thermodynamic Interpretation on the Rheology of Aqueous Bentonite Suspensions

Since their exceptional rheological behavior, bentonite suspensions are widely used in engineering, industrial, agricultural, and drilling applications. So, the aim of the present study is to investigate the rheological properties of three types aqueous suspensions prepared with calcium bentonite (CaB), sodium bentonite (NaB) obtained from that by Na2CO3 activation, and NaB with the excess soda. The CaB taken from Giresun/Turkey region contains calcium smectite (CaxS) as clay mineral and opal CT (SiO2.nH2O) as impurity which is paracrystalline silica. Soda content by the activation and bentonite content in the suspension were changed in the interval of 2.5-15.0% and 5-20% by mass, respectively. CaxS completely converted to sodium smectite (Na2xS) by the activation with the soda content of 2.5% and then Na2xS+Na2CO3 mixtures formed. Rheological properties of these aqueous suspensions were measured using a Fann Viscometer. These properties reached their maxima by the most thixotropic Na2xS suspensions and greatly increased with the increasing of smectite content. Rheological plots drawn of the shear rate vs. shear stress in the interval of 170-1020 s-1 showed that the suspensions flow as a Bingham Plastic. Change in rheological properties depending on the smectite type and content as well as excess soda content was explained thermodynamically based on the chemical potential gradient between interlayer and dispenser waters.

Controllable preparation of Na2Ti6O13 whiskers and their high reflectivity in UV-VIS-NIR

Na2Ti6O13 whiskers were prepared by a molten salt method using Na2CO3, TiO(OH)2 as raw materials and NaCl as the salt. The effects of the calcining temperatures, weight ratios of salt/reactant, and the molar ratios of Na2CO3/TiO(OH)2 on the morphology and phase composition of the products were investigated. The results showed that single-phase Na2Ti6O13 whiskers can be synthesized from a mixture of Na2CO3, TiO(OH)2 and NaCl when calcined at 900 °C for 3 h. We also proposed a synthetic mechanism. Moreover, the thermal conductivity of the Na2Ti6O13 was 0.729 W/(m.k) and the reflectivity among 500–1500 nm of the synthesized Na2Ti6O13 whiskers reached 90%, and have relatively high reflectivity from 350 nm to 400 nm, which indicated that Na2Ti6O13 was a highly reflective energy-saving material.

Rapid Nucleation of Reduced Graphene Oxide-Supported Palladium Electrocatalysts for Methanol Oxidation Reaction.

Small sized electrocatalysts, which can be obtained by rapid nucleation and high supersaturation are imperative for outstanding methanol oxidation reaction (MOR). Conventional microwave synthesis processes of electrocatalysts include ultrasonication, stirring, pH adjustment, and microwave irradiation of the precursor mixture. Ethylene glycol (EG), which serves as a reductant and solvent was added during the ultrasonication or stirring stage. However, this step and pH adjustment resulted in unintended multi-stage gradual nucleation. In this study, the microwave reduction approach was used to induce rapid nucleation and high supersaturation in order to fabricate small-sized reduced graphene oxide-supported palladium (Pd/rGO) electrocatalysts via the delayed addition of EG, elimination of the pH adjustment step, addition of sodium carbonate (Na₂CO₃), prior microwave irradiation of the EG mixed with Na₂CO₃, and addition of room temperature precursor mixture. Besides its role as a second reducing agent, the addition of Na₂CO₃ was primarily intended to generate an alkaline condition, which is essential for the high-performance of electrocatalysts. Moreover, the microwave irradiation of the EG and Na₂CO₃ mixture generated highly reactive free radicals that facilitate rapid nucleation. Meanwhile, the room temperature precursor mixture increased supersaturation. Results showed improved electrochemically active surface area (78.97 m² g-1, 23.79% larger), MOR (434.49 mA mg-1, 37.96% higher) and stability.