Untreated Catalyst Research Articles

Enhanced Platinum-Based Thin-Film Catalysts for Electro-Oxidation of Methanol

Surface morphology is one of the critical factors affecting the performance of electrocatalysts. Thus, with careful manipulation of the surface structures at the atomic level, the effectiveness of the catalyst can be significantly improved. Heat treatment is an effective method for inducing surface atom rearrangement, hence modifying the catalyst’s characteristics. This study investigated the substrate’s influence and the effect of thermal annealing on the morphology and surface reconstruction of platinum (Pt) thin-film catalysts. Our findings indicate that heat treatment in a reductive atmosphere (95% Ar + 5% H2) at 300 °C can significantly impact the degree of rearrangement of surface atoms. This process induces long-range ordering, resulting in domains with a high proportion of (111) and (100) sites without an epitaxial template. Considering that the reactivity of low-index platinum single crystals for the methanol oxidation reaction follows the following sequence Pt(111) < Pt(110) < Pt(100), increasing the proportion of (100) planes leads to a notable enhancement (up to three times) in performance, compared to untreated catalysts. Furthermore, considering the amount of precious metal consumed, a mass-specific current density obtained on annealed Pt@Ni is larger by one order of magnitude and ~2 times that obtained on Pt@Cr and Pt@GCox catalysts, respectively. Our results demonstrate that an easy-to-implement way of controlling atomic orientations improves catalyst performance. With this contribution, we propose a method for designing improved electrocatalysts, as catalytic reactions occur only at the surface.

Nanosized Silica-Supported 12-Tungstophosphoric Acid: A Highly Active and Stable Catalyst for the Alkylation of p-Cresol with tert-Butanol

12-Tungstophosphoric acid supported on nanosilica (TPA/SiO2) was employed as a catalyst for the tertiary butylation of p-cresol using tertiary butanol as an alkylating agent. The TPA/SiO2 catalyst was synthesized using the wet impregnation method followed by steaming at 150 °C for 6 h. The catalysts were characterized by means of X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis. The surface acidity of the untreated and steamed catalysts was characterized via FTIR and DSC thermal analysis using pyridine as a probe molecule. The fresh and spent catalysts were characterized via TGA analysis. The catalytic activity studies showed that the steamed catalyst displayed higher activity, with a higher desired yield of 2-tert-butyl cresol (2-TBC) compared to the untreated catalyst, and that this activity was related to the presence of stronger Brønsted acid sites in the steamed catalyst. A detailed analysis of the TPA/SiO2 steamed catalyst was performed to study the effects of reactant time-on-stream, reactant feed rate, reaction temperature, and the molar ratio of tert-butanol to p-cresol. The optimum reaction temperature, tert-butanol/p-cresol molar ratio, feed rate, and time-on-stream were 413 K, a molar ratio of 2:1, 6 mL/min, and 2 h, respectively. The present study demonstrates that the TPA/SiO2 catalyst exhibits high activity in terms of % conversion and high % selectivity of 2-TBC under the optimized conditions. The characterization of fresh and spent catalysts confirmed the occurrence of coke deposition after the catalytic reaction. The catalyst was regenerated via heat treatment at 400 °C for 5 h. The regenerated catalyst was reused for subsequent runs for three cycles without showing a loss in its activity.

CuO–TiO2 pilot-plant system performance for solar photocatalytic hydrogen production

The main goal of the present study was to explore photocatalytic performance of the TiO2–CuO mixture, for solar to hydrogen conversion at pilot plant scale under two different irradiation conditions (sunny and partly cloudy), focusing on high-temperature pretreatment of the catalyst mixture to try to improve TiO2 doping with copper. P25–TiO2 and commercial CuO were used with different amounts of Cu (2 wt% or 7 wt% Cu) calcined at 200–400 °C during several hours. Catalysts were tested at pilot plant scale using solar compound parabolic collectors, with glycerol as the sacrificial agent. The photocatalyst prepared after heating at 200 °C for 3 h and with 7 wt% Cu, resulted in higher hydrogen production than under the other heating conditions, and results were slightly better (5–10%) than the reference values with the untreated catalysts. Photocatalytic efficiency was slightly lower at the higher calcination temperature (400 °C). CO2 production and formation of formate and glycolate clearly demonstrated glycerol photoreforming. The Cu from the calcined catalyst remaining on the solid was significantly less (2.5%) than on the non-calcined catalyst (4.2%), with an important fraction of lixiviated copper and copper deposition on the reactor walls. This is a critical drawback that must be considered for large-scale applications.

Tailoring chemoselectivity of Fe/Ni catalyst for hydrogenation of carbonyl compound

Selective hydrogenation of carbonyl moiety in the presence of olefinic group and other reducible functionality is an industrially important transformation. However, the protocol of green chemistry cannot be sacrificed for its formidable challenging transformation. Therefore, iron nickel bimetallic recyclable catalyst (Fe/Ni) was used for base free hydrogenation of carbonyl compound with high activity and chemoselectivity in microwave environment. The microwave irradiation and pre-treatment of bimetallic catalyst (Fe/Ni) divert conversion/selectivity towards CO group as compared to CC or another reducible moiety. This is further confirmed by DFT calculations which shows that the CO site is strongly interacted with the surface compared to the CC site. The pyridine adsorption studies revealed that pre-treated (Fe/Ni) possess more acidic sites as compared to untreated catalyst. Furthermore, the selectivity of bimetallic catalysts towards hydrogenation of carbonyl function group was correlated with Fe content present in the matrix of catalyst.

Impact of pretreatment and thiol modifiers on the partial oxidation of glutaraldehyde using Pd/Al2O3

Oxidative conversion of biomass-derived compounds to value-added chemicals is challenging due to the tendency of multi-functional reactants to overoxidize. Catalyst performance can be sensitive to both synthesis and pretreatment conditions. Additionally, coating the catalyst with self-assembled monolayers (SAMs) has shown promise in modulating activity and selectivity. Here, the liquid-phase partial oxidation of glutaraldehyde (GA) to glutaric semialdehyde (GSA) was investigated as a model reaction using a Pd/Al2O3 catalyst, with and without various thiolate SAM modifiers. Reductive pretreatment of the catalyst showed enhancement in the activity and a shortening of an apparent induction period relative to the untreated catalyst. The selectivity for GSA was further found to be sensitive to the identity of the SAM layers, with hydrophilic thioglycerol (TG) and thiolactic acid (TLA) coatings showing an enhancement in selectivity to GSA; the TG coating raised selectivity from ∼ 60 % (on uncoated catalyst and catalysts coated with hydrophobic thiols) to ∼ 80 % at identical conversion (∼ 30 %). However, the TG coating exhibited lower catalytic rates compared to UC and hydrophobically coated materials. Morphological and electronic causes were ruled out with various materials characterization techniques. Density functional theory (DFT) calculations suggested that hydrogen bonding stabilizes adsorption of GSA compared to the uncoated Pd surface. However, a large stabilization of glutaric acid (GAC) adsorption for TG-coated Pd was also predicted, likely leading to accumulation of this overoxidation product and lower overall rates. Inhibition of the rate of GA partial oxidation by GAC adsorption was then corroborated experimentally. Finding ways to stabilize the less-oxidized intermediates with more specificity is thus suggested as a strategy to improve rate and selectivity.

Improved metal-support interaction in Ru/CeO2 catalyst via plasma-treated strategy for dichloroethane oxidation

Plasma-treatment strategy has become an important technique to modify heterogenous catalyst. Here, the plasma-treated Ru/CeO2 catalysts were synthesized and applied to dichloroethane (DCE) oxidation. Compared with the untreated catalysts (CeO2-T and Ru/CeO2-T), the plasma-treated catalysts (CeO2-P, Ru/CeO2-P and Ru/CeO2-TP) show higher catalytic activity. Amongst, the Ru/CeO2-P catalyst shows the highest activity (T90 =243 °C, TOFSSA=6.98 μmol·m−2·h−1 and Ea=26 kJ·mol−1). Based on various characterizations, it reveals that the plasma-treatment can enrich the concentration of surface oxygen vacancies, promote the formation of acid sites, and strengthen the interaction between Ru and CeO2 support. The interaction benefits the dispersion of Ru species, forming more active sites to enhance the DCE conversion. The more acid sites can improve the HCl selectivity. Moreover, the Ru/CeO2-P catalyst exhibits excellent thermal stability and water-resistance performance. This signification result promotes the development of catalysts by plasma-treated strategy, and its wide application in heterogenous catalysis.

Boosting the Activity of Pd Single Atoms by Tuning Their Local Environment on Ceria for Methane Combustion

AbstractSupported Pd single atom catalysts (SACs) have triggered great research interest in methane combustion yet with contradicting views on their activity and stability. Here, we show that the Pd SAs can take different electronic structure and atomic geometry on ceria support, resulting in different catalytic properties. By a simple thermal pretreatment to ceria prior to Pd deposition, a unique anchoring site is created. The Pd SA, taking this site, can be activated to Pdδ+ (0<δ<2) that has greatly enhanced activity for methane oxidation: T50 lowered by up to 130 °C and almost 10 times higher turnover frequency compared to the untreated catalyst. The enhanced activity of Pdδ+ site is related to its oxygen‐deficient local structure and elongated interacting distance with ceria, leading to enhanced capability in delivering reactive oxygen species and decomposing reaction intermediates. This work provides insights into designing highly efficient Pd SACs for oxidation reactions.

Boosting the Activity of Pd Single Atoms by Tuning Their Local Environment on Ceria for Methane Combustion.

Supported Pd single atom catalysts (SACs) have triggered great research interest in methane combustion yet with contradicting views on their activity and stability. Here, we show that the Pd SAs can take different electronic structure and atomic geometry on ceria support, resulting in different catalytic properties. By a simple thermal pretreatment to ceria prior to Pd deposition, a unique anchoring site is created. The Pd SA, taking this site, can be activated to Pdδ+ (0<δ<2) that has greatly enhanced activity for methane oxidation: T50 lowered by up to 130 °C and almost 10 times higher turnover frequency compared to the untreated catalyst. The enhanced activity of Pdδ+ site is related to its oxygen-deficient local structure and elongated interacting distance with ceria, leading to enhanced capability in delivering reactive oxygen species and decomposing reaction intermediates. This work provides insights into designing highly efficient Pd SACs for oxidation reactions.

Quantifying and Understanding PGM-Free Oxygen Reduction Reaction Active Sites by in Situ Molecular Probes

Gaining a better understanding of PGM-free oxygen reduction reaction (ORR) catalyst active site structure and activity relationships is key to developing more active catalysts. Active sites in a variety of Fe-N-C catalysts including commercial Pajarito Powder catalyst, with a range of activity and durability, were studied via in situ catalyst poisoning using thiol-molecular probes. The selectivity and extent of catalyst de-activation by the probes was monitored by comparing changes in ORR activity of the catalysts and N-containing carbon materials. Electrochemical stripping of the molecular probe was used to calculate the concentration of available active sites. These experiments were coupled with catalyst degradation and Fe-leaching experiments to better understand the specificity of the molecular probe binding. Probe-treated and untreated catalysts were also characterized using XPS. We plan to use these methods to better understand structural factors of the Fe-N-C active site, as well as the surrounding NC structure that may influence catalyst activity or durability.This work was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) through Electrocatalysis Consortium (ElectroCat).

Improvement of fuel cell catalyst performance through zirconia protective layer coating by atomic layer deposition

In this study, the performance of the cathode catalyst of polymer electrolyte membrane fuel cells is improved by the atomic layer deposition (ALD) of a protective layer. An atomic layer-scale zirconia protective layer is coated on the platinum catalyst for surface treatment. The results indicate that a very thin layer deposition with two ALD cycles or less is required to minimize the deterioration of the activity of the catalyst. Further, it is also confirmed that the catalyst aggregation can be effectively suppressed by its encapsulation with the protective layer through several ALD cycles from the analysis of the electrochemical surface area by cyclic voltammetry and the change in the catalyst particle size. According to the results, even two ALD cycles, which provide less than one atom layer, has decreased the deterioration rate to one-fourth of that of the untreated catalyst, with a minor decrease in the fuel cell power. In addition, the I–V data and impedance spectroscopy confirms that the overall stability of the membrane electrode assembly is improved by the ALD treatment. Thus, the ALD of a protective layer is considered to be a very promising strategy to improve the stability and performance of fuel cell catalysts.

Effect of water treatment and Ce doping of Pt/Al2O3 catalysts on Pt sintering and propane oxidation

The effect of Ce doping and pretreatment of Pt/Al2O3 on its catalysis of propane oxidation was investigated after aging the catalysts. The Ce amount and pretreatment conditions were varied, and the propane oxidation activity was measured. The properties of the catalysts were investigated by means of XRD, STEM-EDX, FT-IR, and H2-TPR. The size of the Pt nanoparticles (PtNPs) decreased for water-treated catalysts doped with a small amount of Ce, suggesting that water treatment of Ce-doped catalysts inhibits Pt sintering. The minimum PtNP size was obtained with ca. 3.6 wt% of Ce. The Ce species with less than 3.6 wt% existed in a dispersed state, whereas above this value, CeO2 particulates co-existed. The propane oxidation temperature of the water-treated catalysts was lowered to an extent that depended on the Ce content. This tendency is consistent with the PtNP size in the catalysts. It is considered that highly dispersed Ce species take a primary role in promoting propane oxidation on PtNPs. The reduction temperature of Ce species on water-treated catalysts was lower than that of untreated catalysts, probably owing to a stronger interaction between Pt and Ce, demonstrated by FT-IR measurements. The increased reducibility of Ce species may be the reason for the improved oxidation activity of the catalysts.

Probing Hydrophobization of a Cu/ZnO Catalyst for Suppression of Water–Gas Shift Reaction in Syngas Conversion

Due to the complexity of the structure and surface property of metal oxide catalysts, hydrophobization of metal oxide catalysts is a great challenge. The hydrophobization strategy and effects of hydrophobization on the surface property and catalytic performance of metal oxide catalysts deserve rigorous investigations. Herein, we adopt stearic acid to functionalize the surface of a Cu/ZnO catalyst by bridging stearic acid molecules with the Cu/ZnO catalyst surface. After functionalization, the hydrophobicity of the Cu/ZnO catalyst is greatly reinforced, while its structure and catalytic performance remain nearly unchanged. The hydrophobic Cu/ZnO catalyst exhibits a very positive inhibitory effect on the unfavorable water–gas shift reaction (WGSR) in one-step synthesis of dimethyl ether (DME) from syngas (CO + H2), while the catalytic activity of the hydrophobic Cu/ZnO catalyst for methanol synthesis is not affected. Lower CO2 selectivity and higher DME selectivity over the hydrophobic Cu/ZnO-4 catalyst, better than those of untreated catalyst, are obtained facilely. The promoted catalytic performance of the hydrophobic Cu/ZnO catalyst demonstrates that the surface hydrophobicity of heterogeneous catalysts is worthy of more attention for enriching their catalytic roles.

Enhancements in catalytic activity and duration of PdFe bimetallic catalysts and their use in direct formic acid fuel cells

The palladium–iron based bimetallic catalysts (PdxFey/Cs) and facile synthetic method are introduced to enhance the catalytic activity and operational duration for direct formic acid fuel cells. To improve the properties of PdxFey/C catalysts, such as degree of PdFe alloy and its crystallinity, heat treatment is conducted at 600°C. According to results, the Pd–Fe bond and Fe metal particle are formed after the heat treatment, while iron oxides and Pd particles are observed in the untreated samples. Electrochemical evaluations for measuring the formic acid oxidation reaction rate demonstrates heat treated Pd3Fe1/C (HT-Pd3Fe1/C) is the best catalysts of six samples which are synthesized by using different Pd to Fe ratios (3:1, 1:1, 1:3) before and after heat treatment. This is because the HT-Pd3Fe1/C has high Pd–Fe alloying and Pd contents. Through the heat treatment, the indirect formic acid oxidation reaction way is activated and the resistance to CO poisoning is significantly improved. The maximum power density of direct formic acid fuel cells using HT-Pd3Fe1/C whose open circuit voltage is 0.83V is 137mWcm−2, which is 1.6 and 1.9 times higher than that of direct formic acid fuel cells using untreated catalyst and Pd/C.

PtNix/C Catalysts for Improved Performance in Ethanol Fuel Cells

PtNix/C catalysts were synthesized in various solvents by using a polyol method and were then treated with acetic acid. They were characterized by X-ray powder diffraction, thermal gravimetric analysis and energy-dispersive X-ray spectroscopy. Electro-chemical analysis was carried out by cyclic voltammetry and chronoamperometry to study the activity of these catalysts toward the oxidation of ethanol. Moreover, a commercial PtNi0.26/C catalyst was evaluated using the same methods for comparison. A PtNi0.62/C(PG) catalyst prepared in propylene glycol was more active toward the oxidation of ethanol than a catalyst prepared in the same way in ethylene glycol and the commercial PtNi0.26/C, exhibiting less poisoning by adsorbed CO. Treatment with acetic acid to remove surface Ni further enhanced the activity toward ethanol oxidation. For example, the activity of treated PtNi0.62/C(PG) was 11.6 mA mg−1 at 0.27 V while it was 6.7 mA mg−1 for the untreated catalyst.

Enhanced photocatalytic activity of biosynthesized Au-Ag/TiO2 catalyst by removing excess anchored biomolecules

A green bioreduction method was used to prepare highly efficient supported TiO2 photocatalysts with bimetallic (Au-Ag) nanoparticles at room temperature using Cinnamomum camphora leaf extract as both the protective agent and reducing agent. The resulted Au-Ag/TiO2 exhibits high photocatalytic activity toward the degradation of organic dyes. It was demonstrated that after some of the biomolecules were removed through ionic-liquid extraction and/or calcinations, the Au-Ag/TiO2 photocatalyst exhibits significantly enhanced catalytic performance toward the degradation of methyl orange compared to the pristine untreated catalyst. As a result, 300 mL of 20 mg/mL methyl orange can be fully degraded in 30 min. These can be explained by the sufficient biomolecules could protect the nanoparticles stay in small size, but excess biomolecules played an unfavorable role in hindering the electron transportation during the catalytic reaction. The low-cost preparation, the high activity, together with the good stability and recyclability make this developed Au-Ag/TiO2 a promising photocatalyst toward the degradation of wastewater.

Metal Oxides Derived from Modified Hydromagnesite: Evaluation of Their Catalytic Activity in the Synthesis of Ethyl Biodiesel

AbstractBiofuels are already part of the energy matrix in many countries because of their environmental and economic benefits. Ethyl biodiesel can be produced by various processes, the main one being transesterification of triglyceraldehydes and ethanol. The current technological challenge is to develop efficient heterogeneous catalysts, at low cost, non‐polluting and recyclable to be used in this process. In this context, hydromagnesites Mg5(CO3)4(OH)2⋅4H2O modified with different cations (Ca2+, Zn2+, Cu 2+, Ba2+) and synthesized by co‐precipitation are used as precursors of catalytic oxides calcined at 600 °C. The biodiesel synthesis was conducted at 120 °C for 12 h using 20% (w/w) of catalyst per mass of soybean oil and the ratio 1:20 (mol/mol) of soybean oil/ethanol. The alkyl esters formed were quantified by Gas Chromatography‐Flame Ionization Detection (GC‐FID). The transesterification reaction catalyzed by the reference oxide had a yield of 40%, whereas the best yield (80%) came from the hydromagnesite modified with 20% of Ca2+ which also had the highest basicity/acidity ratio. After use in three reaction cycles, the catalyst with 20% Ca2+ had no significant reduction in efficiency when it was washed with acetone and recalcined at 600 °C, while the untreated catalyst only had a yield of 42%, showing the need for effective reconditioning.

Effect of the non-thermal plasma treatment on the structure and SCR activity of vanadium-based catalysts

A catalyst V-Ce-Ni/TiO2 was synthesized using the ultrasound-assisted impregnation, and the catalysts V-Ce-Ni/TiO2-NP and V-Ce-Ni/TiO2-HP were prepared by N2 and H2 non-thermal plasma-treatment, respectively. The structure and catalytic activity of the catalysts was characterized and evaluated in the study. BET results indicated that the specific surface area over V-Ce-Ni/TiO2-NP catalyst (50 m2·g−1) was higher than that of untreated catalyst (49 m2·g−1). And the characterization results of XRD, TEM, SEM and EDS showed that the plasma treated catalysts have smaller particle size, higher dispersion and better uniform distribution of active sites on the catalyst surface than the untreated catalyst. Besides, the results of XPS and NH3-TPD revealed that non-thermal plasma treatment generated more oxygen vacancy on the catalyst surface than the untreated catalyst, and then increased the amount of acid sites. H2-TPR results suggested that the interaction between active components and support (TiO2) of V-Ce-Ni/TiO2-HP was stronger than that of V-Ce-Ni/TiO2-NP. The results of NH3-SCR (selective catalytic reducing of NO with ammonia) showed that above 90% of NO conversion was obtained over V-Ce-Ni/TiO2-HP catalyst in the temperature ranging from 195 °C to 414 °C, and 100% of NO conversion was maintained in the temperature regions of 230 °C to 350 °C. The catalytic activity of the catalysts of non-thermal plasma treatment was enhanced at low temperature (below 260 °C), and the operating temperature window (T90) of the catalysts was widened.

Vibrating Powders: Eqcm Measurement of Potential Dependent IrO2 Mass Changes for Voltage Reversal Tolerant PEMFC Anodes

Oxygen evolution reaction (OER) catalysts are used to protect carbon components of polymer electrolyte membrane fuel cell (PEMFC) anodes during transient fuel starvation conditions such as start-up/shut-down [1]. OER catalysts such as IrO2 or RuO2 promote the oxidation of water instead of the corrosion of carbon components [1, 2]. However, the conditions in a PEMFC during normal operation (ca. 0 V and low pH) can induce instability in these metal oxides. IrO2 in particular can form soluble Ir3+ species [3] that migrate across the membrane electrode assembly and deposit on the cathode causing poisoning of the oxygen reduction reaction (ORR) catalyst (typically Pt/C). Currently, OER catalysts for reversal tolerant anodes (RTAs) are investigated using prototype MEA single unit cell testing which is time consuming and expensive to perform [4]. Previously, our group investigated the dissolution of different IrO2 based powder catalysts using a potential stepping stress test. The dissolution of Ir3+ from this test was compared with reversal tolerance of a membrane electrode assembly fabricated using the same IrO2 catalyst [5]. To further investigate the dissolution of IrO2 powders, we have devised a series of experiments (with potential cycling between 0.05 to 1.2, 1.4 and 1.6 V, at 100 mV s-1 30 times each and 298 K) using the electrochemical quartz crystal microbalance (EQCM) technique. The EQCM uses a vibrating quartz crystal and measures its frequency (inversely proportional to crystal mass) as a function of potential. Our method was validated using a commercially available IrO2 powder (Alfa Aesar) heat treated in air at 350, 450 and 550°C which improves durability while negatively effecting OER activity [6]. The powders were deposited (24 μ cm-2) onto a gold EQCM crystal to investigate the dissolution behavior as a function of particle size, crystallinity and electrode potential. The untreated IrO2 exhibited a large irreversible increase in vibration frequency indicating a loss of mass during the initial polarization from 1.2 to 0.05 V. The increase was on the order of 400 to 700 Hz or -7.1 to -12.4 μg cm-2 assuming a perfectly uniform and rigid layer (figure a). This frequency increase could equally be due to loss of adhesion from the surface, a change in the rigidity of the layer or dissolution of Ir3+. To confirm that frequency changes were not due to adhesion or rigidity of the film, samples of the electrolyte were taken from near the electrode surface and Ir3+ concentration was determined by inductively coupled plasma mass spectrometry (ICP-MS). We observed that the frequency of the untreated IrO2 increased by ca. 90 Hz (-1.6 μ cm-2) during a single polarization from 0.05 V to 1.2 V (figure a). Birss et al. reported the formation of an iridium oxo-hydroxide which causes a mass increase when polarizing to 0 V [6]. Conversely, the frequency of heat treated layers first decreased by ca. 200-500 Hz (1.4 to 3.5 μg) then increased again when polarizing to 1.6 V. Heat treatment induced IrO2 crystallinity changes could account for this difference in frequency response. From the first cycle to the last, there was a frequency gain for untreated IrO2 and a frequency loss for all of the heat treated IrO2 catalysts; suggesting Ir3+ dissolution and increased IrO2 layer rigidity or coverage respectively. The capacitive current of the untreated catalyst decreased slightly over the course of the test and was more than five times higher than the 550°C heat treated catalyst in its cyclic voltammogram (figure c and d). The main challenge to using EQCN for powder catalyst investigation is producing layers with consistent and repeatable frequency behavior. In this work, the IrO2 deposition conditions were tightly controlled and each experiment was repeated to ensure the consistency of the results. If these obstacles can be overcome, EQCN presents a novel, rapid and powerful tool to learn about the potential dependent reactions taking place using a myriad of catalyst materials. Ralph TR, Hudson S, Wilkinson DP (2006) ECS Trans 1:67–84.Patterson TW, Darling RM (2006) Electrochem Solid-State Lett 9:A183–A185.Danilovic N, Subbaraman R, Chang K-C, et al (2014) J Phys Chem Lett 5:2474–2478.Makharia R, Kocha S, Yu P, et al (2006) ECS Trans 1:3–18.Moore CE, Eastcott J, Cimenti M, Kremliakova N, Gyenge EL (2019) J Power Sources in review da Silva GC, Perini N, Ticianelli EA (2017) App Cat B: Env 218 287–297.Birss VI, Elzanowska H, Gottesfeld S (1991) J Electroanal Chem and Interfac Electrochem 318:327–333. Figure 1

A Composite Catalyst Based on Perovskites for Overall Water Splitting in Alkaline Conditions

AbstractElectrochemical water splitting is considered a sustainable way to produce H2. However, it is still a challenge to develop efficient and stable electrocatalysts. Here, a bifunctional composite catalyst for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) was constructed by using a facile in situ growth route, which combines the carbonization on exsolved alloy nanoparticles and sulfurization in one continues step. This composite catalyst contains Ruddlesden‐Popper‐type S‐adsorbed (Nd0.6Sr0.4)3((Co,Fe)0.85Nb0.15)2O7, metal sulfides, and hollow S‐doped carbon fibers. Compared to the untreated catalyst, Nd0.6Sr0.4Co0.6Fe0.3Nb0.1O3‐δ, the composite catalyst leads to significantly enhanced OER and HER activities as well as excellent stability (more than 400 h without inactivation) during overall water splitting. Our research offers a new route to fabricate hetero‐architecture materials with S‐doped hollow carbon fibers on alloy nanoparticles of perovskite oxides.

Effects of Aging Treatment on the Hydrotreating Performance of the Unsupported Catalyst

An unsupported Ni–Mo–W catalyst was synthesized by the hydrothermal method and treated by an aging treatment to improve its specific surface area and pore size. The effect of different aging conditions was studied by BET, XRD, SEM, and HRTEM techniques. The catalytic activity of the unsupported catalyst was evaluated with a simulated diesel feed. BET results showed that the catalyst specific surface area and pore volume increased significantly after aging treatment, and the hydrotreating results revealed that aging treatment resulted in higher catalytic activity than untreated catalyst, which is beneficial to the production of Ultra-Low-Sulfur Diesel (ULSD).