Catalyst Deposition Research Articles

Photocurrent improvement from magnetron DC sputtered and thermally treated ruthenium-based catalyst decoration onto BiVO4 photoanodes

Monoclinic BiVO4 (BVO) properties favor its use as the main absorber in photoanodes applied for photoelectrochemical water splitting. However, hindrances as the high rate of recombination of the electrons and holes photogenerated and as the poor charge carrier transport limit its direct, practical use. Doping, building a heterojunction with other semiconductors and decorating the surface with catalysts like cobalt phosphate and ruthenium oxide are among the many existing approaches to improve BVO performance. The deposition of catalyst or cocatalyst normally involve the use of potentially hazardous techniques as chemical vapor deposition (CVD). In this work, we present a simple route for enhancing photoelectrochemical results in BVO samples. The decoration with metallic ruthenium is performed via magnetron sputtering DC, a reliable, inexpensive and safe-to-use physical deposition technique, followed by a thermal treatment in air within a muffle furnace for 6 h at 400 °C. A gain of about 45% in the photocurrent at 1.23 V vs reversible hydrogen electrode (RHE) and in the overall spectrum area in comparison with pristine BVO samples was registered by cyclic voltammetry measurements in a 0.5 M phosphate buffer solution under full spectrum illumination from a 100 W Xenon lamp. The morphological and chemical modifications that resulted in such photocurrent rise were characterized using Scanning Electron Microscopy (SEM), Rutherford Backscattering Spectrometry (RBS) and X-ray Photogenerated Spectroscopy (XPS).

Integrated process of coal pyrolysis with dry reforming of low carbon alkane over Ni/La2O3-ZrO2 with different La/Zr ratio

Integrated coal pyrolysis with dry reforming of low carbon alkane (CP-DRA) is an effective method to improve tar yield. The development of dry reforming catalyst is the key for the integrated process. Ni/La2O3 shows a good performance in improving tar yield during CP-DRA, but the carbon deposition of catalyst is still a lot. To solve this problem, Zr was used as modifier to prepare Ni/La2O3-ZrO2 with different La/Zr ratios (1:1, 2:1, 4:1 and 8:1) by co-precipitation to improve catalyst stability. Results indicated that Ni4LaZr (La/Zr ratio being 4) shows a good performance and high anti-carbon deposition in DRA and CP-DRA as compared to other catalysts. The highest tar yield of CP-DRA over Ni4LaZr at 600 °C is 20.5 wt.%. Ni4LaZr catalyst also shows a good regenerability, and tar yield keeps at 20.3 wt.% within 5 times regeneration, indicating a good stability of Ni4LaZr. The high performance and stability are due to the formation of a stable pyrochlore La2Zr2O7 and present of excess La2O3 in Ni4LaZr that can inhibit carbon deposition.

Formation of perovskite-type LaNiO3 on La-Ni/Al2O3-ZrO2 catalysts and their performance for CO methanation

The carbon deposition and sintering of Ni-based catalysts, used in CO methanation, are the main problems to be solved. In this paper, supported LaNiO3/Al2O3-ZrO2 catalyst was prepared by neutralization hydrolysis-citric acid complexation method. The effects of La-Ni loading and calcination temperature of support on the structure and catalytic activity of the catalyst were investigated. The structural evolution of catalyst precursor before and after reduction was studied via XRD, H2-TPR, BET, XPS, TEM and other characterization methods. The results showed that the catalyst supported by homogeneous Al-Zr solid solution was beneficial to form the active component with LaNiO3 structure, and the Ni0 derived from LaNiO3 was the key factor for keeping the activity at high temperature. The La-Ni loading affected the formation of LaNiO3 and the reduction state of Ni. Among the catalysts studied, 30% of the La-Ni loading was more favorable for the formation of perovskite LaNiO3. The Ni0 and La2O3 reduced from LaNiO3 were highly dispersed on the surface of the support, and the Ni0 nanoparticles were anchored by the support and La2O3, which inhibited the migration and aggregation of Ni0 particles at high temperature and thus led to high thermal stability.

Kinetic assessment of H2 production from NH3 decomposition over CoCeAlO catalyst in a microreactor: Experiments and CFD modelling

A flat-plate microreactor was designed, examined and modelled for the on-board hydrogen generation via the ammonia decomposition reaction over CoCeAlO mixed oxide catalyst. The tested catalyst was synthesised and immobilised using an inkjet printing-assisted self-assembly method. Inkjet printing technology is proved to be an efficient way for the direct synthesis, deposition and rapid screening of heterogeneous catalysts. A series of kinetic experiments were performed to analyse the influence of reaction temperature and NH3 flow rate on the microreactor performance. Two kinetic rate expressions were developed based on the conversion data and implemented in the CFD model. The simulation results showed good accuracy with respect to the experimental data, and the kinetic models could effectively predict the reacting flow properties along the microchannel. The microreactor is especially designed to operate under the kinetic-control conditions with negligible mass transfer resistance. Furthermore, the proposed design eases the assemblage and disassemblage of the microreactor components, and the probing of fresh catalysts for kinetic studies.

Исследование массива вертикально-ориентированных многостенных углеродных нанотрубок для абсолютно черного тела

An array of vertically oriented multi-walled carbon nanotubes (VOMWCNT), obtained by chemical vapor deposition (CVD) on a silicon substrate without preliminary catalyst deposition, has been comprehensively investigated. The synthesis was carried out for 30 minutes in the reactor of a carbon nanotube synthesis unit under conditions of decomposition of the reaction mixture (ferrocene in heptane) at a temperature of 800 °C at a carrier gas flow rate of 200 ml/min. The structure and geometric characteristics of the array’s carbon nanotubes were determined using scanning and transmission electron microscopy and Raman spectroscopy. The spectral coefficient of diffuse reflection (SDR) into the hemisphere in the wavelength range from 5,0 to 15,0 μm was determined. From the obtained experimental data, it was found that the emissivity (absorption coefficient) of an array of carbon nanotubes with a height of (230 – 250) μm is 0,98 – 0,99 in the spectral range from 5,0 to 13,7 μm and 0,975 – 0,995 in the range from 13,7 to 15,0 μm. Such a VOMWCNT array can be used to develop an absolutely black body with a high absorption coefficient and small mass and size characteristics, which is used for calibrating spacecraft’s infrared spectrometers.

Influence of electrodeposition techniques and parameters towards the deposition of Pt electrocatalysts for methanol oxidation

Deposition of platinum catalysts on a titanium substrate (Pt/Ti) was performed using various electrodeposition techniques, and an optimum deposition condition attributing to enhanced activity towards methanol oxidation reaction (MOR) was identified. Physical characterization confirmed that the variation of deposition parameters resulted in Pt nanostructures with various morphologies. The final morphology of the Pt catalyst was strongly influenced by the average potential applied or observed during the deposition. Dynamic applied waveform electrodeposition techniques, namely cyclic voltammetry deposition and pulse current deposition, were found to offer efficient deposition and homogeneous distribution of Pt on Ti compared to constant applied waveform deposition techniques such as potentiostatic and galvanostatic deposition, which could be attributed to the improved homogeneity of metal ion concentration during deposition. Among the various deposition techniques and parameters studied, results indicate that Pt catalysts deposited by pulse electrodeposition with a low-duty cycle was found to be the optimum to achieve high catalytic activity towards MOR. The results of this study not only reflect the fundamental understanding of Pt morphology at different deposition modes but also highlight the importance of performing the deposition with an optimal deposition technique and parameters to have a better and more efficient metal deposition from its precursor.

Deposition of Noble Metal Catalysts on SiC Wafer by Electroless Process

Deposition of Noble Metal Catalysts on SiC Wafer by Electroless Process

Scale-up of Metal-Supported Solid Oxide Fuel Cells

Metal-supported solid oxide fuel cells (MS-SOFC) offer the advantages of low-cost structural materials (e.g. stainless steel), mechanical ruggedness, excellent tolerance to redox cycling, and extremely fast start-up capability. Because of rapid-start capability, MS-SOFCs may be well-suited for portable, ruggedized, fast-start, intermittent-fuel, transportation, or other unique and innovative applications. The LBNL approach focuses on symmetric-architectured, co-sintered, ScSZ-based MS-SOFCs with porous metal supports on both anode and cathode sides, and catalysts deposited into both electrodes via infiltration (Fig 1). These features provide for a mechanically rugged cell that can be processed with low-cost scalable techniques, and for high surface-area catalysts that are deposited after sintering, thereby avoiding interdiffusion or coarsening during cell sintering.LBNL’s previous work on MS-SOFCs includes demonstration of A) Over 1000h operation in both hydrogen fuel cell and steam electrolysis modes [1,2], B) stable operation with direct internal reforming of ethanol-water blend fuel [3], C) startup within 10 sec for a bare cell and more than 200 rapid thermal cycles for a cell mounted on a test rig manifold [1,4], D) dynamic load-following with operating temperature fluctuating rapidly under load [5], and E) tolerance to multiple deep redox cycles [1].Previous demonstrations were achieved with button cells in the range 3 to 7 cm2 total cell area. In this work, the MS-SOFC cell area is scaled up to 50 cm2 and higher, Fig 2. Scale-up of the stainless steel and zirconia cell architecture is straightforward. The cell structure is prepared by tapecasting large sheets and laser cutting to size, which is amenable to making any size or shape cell. Due to the symmetric nature of the cell architecture, the large cells remain flat after sintering.Uniform catalyst deposition over a large area is, however, challenging. A number of improvements to the infiltration technique were developed, including: pre-oxidation of the stainless steel to enhance wetting of the aqueous catalyst precursor solution into the porous cell surface; development of highly concentrated Pr-oxide and Ni/doped-ceria precursor solutions that are shelf stable and low-viscosity; and, aerosol spray deposition of those solutions to uniformly coat the entire cell. With the improved infiltration, nearly identical performance for button and large cells is achieved. Spray deposition of shelf-stable aqueous solutions is also anticipated to be much more relevant to industrial-scale cell manufacturing, relative to LBNL’s previous molten salt infiltration technique.AcknowledgementsThe information, data, or work presented herein was funded in part by the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy under work authorization numbers 13/CJ000/04/03 and 18/CJ000/04/01. Funding for this work was provided by LBNL and the U.S. Department of Energy Advanced Manufacturing Office through a Technology Commercialization Fund grant number TCF-18-15740. This work was funded in part by the U.S. Department of Energy under contract no. DE-AC02-05CH11231.References Tucker, M.C., J. Power Sources 369 (2017) 6-12Shen, F., R. Wang, and M.C. Tucker, in preparationDogdibegovic, E., Y. Fukuyama, M.C.Tucker, Journal of Power Sources, 449 (2020) 227598Tucker, M.C., and A.S. Ying, International Journal of Hydrogen Energy, 38 (2017) 24426-24434Tucker, M.C., J. Power Sources, 395 (2018) 314-317 Figure 1

Effect of Polarity of Surfactant on Formation of through-Silicon Via Using Metal-Assisted Chemical Etching

In this study, we demonstrated formation of high aspect vertical holes in Si substrate using wet chemical approach, MacEtch process, for the application of through silicon via (TSV) holes. It is important that the addition of the surfactants in the etching solution to obtain the well- defined straight holes in the Si substrate using MacEtch, regardless the polarity of the surfactants. MacEtch is expected to be used for formation of TSV instead of Deep reactive ion etching (Deep-RIE) because of lower costs than Deep-RIE [1,2,3]. However, it is difficult to obtain high aspect vertical holes using MacEtch process due to its instability of etching direction for prolonged process as shown in Fig. 1(a). Addition of surfactant is usefulness to improve the morphology of etched holes. Micro scale holes were prepared in N-type Si (100) substrate using MacEtch process. The disc shape Au deposited by sputtering were used as catalyst. Before deposition of the Au catalyst, a Ti interlayer with a thickness of 10 nm was deposited directly on the Si substrate with patterned resist. The patterned Au discs (10 μm in diameter), which were deposited on a Ti / Si substrate using a photolithography lift-off process. The thicknesses of deposited Au were 10 nm for Ti/Si substrate. The base pressure of the deposition chamber was maintained at 10-5 Pa, and purity of Au and Ti target used for the deposition were 99.99 %, respectively. For the MacEtch process, a mixture of 1.0 M hydrofluoric acid (HF), 1.3 M hydrogen peroxide (H2O2) and deionized water was used as the base etching solution. Benzalkonium chloride (BKC), and polyethylene glycol (PEG), which were cationic and non-polar surfactant, respectively, were used as the additive for the etching solutions. The MacEtch of the Si substrate with patterned Au were performed for 120 min at 40 oC in the etching solution. Fig.1 shows cross sectional SEM images of typical shape of etched Si holes using MacEtch. The direction of etched Si hole was changed during MacEtch without surfactants, as shown Fig.1 (a), and these changes of direction occurred more than 60% Si holes. By contrast, we observed drastic improvement on direction of etched holes in almost all holes in addition of PEG, as indicated Fig.1 (b). Similarly, adding BKC in MacEtch process was also observed improvement. The catalyst at the bottom of substrate without surfactant was deformed and partially detached from the Si substrate, as shown Fig.1 (d). However, with PEG and BKC, the catalyst contacted to the bottom and was suppressed deformation, as indicated Fig.1 (e), (f). In addition, BKC suppressed at 25 times low concentration compared with PEG. This phenomenon was is considered due to influence of polarity of hydrogen part or structure of surfactants. Particularly, the shape of catalyst film with BKC kept flat during MacEtch process compared with PEG. Therefore, defamation of catalyst has a strong correlation with formation of bended holes. Moreover, the suppression effect of catalyst is stronger in cation, BKC, than in non-ion, PEG.

(PEFC&E 2nd Place Best Poster Winner) Simulation of Reaction and Mass Transport in PEFC Cathode Catalyst Layer Fabricated by Inkjet Printing Method

Polymer electrolyte fuel cell (PEFCs) is a potential power source for new-generation automobiles like fuel cell vehicles that run on hydrogen energy, it has been studied a lot for last decades in order to use as the power sources of automotive. The most important characteristics of PEFCs are low operation temperature and quick start and shutdown. However, the properties of PEFCs are still limited due to its high cost and insufficient durability and performance.Since oxygen reduction reaction (ORR) at the cathode is the dominant reaction in PEFCs, oxygen proton and electron have to be transferred smoothly in porous catalyst layer. Under normal operating conditions, oxygen transfer is the dominant factor of limiting current density, therefore, oxygen transfer must be increased from the gas channel to the Pt surface through various porous media and various components.On the other hand, inkjet printing has been considered to be an economical and easy scale-up technology for the micro-scale patterning and fabrication as one of the on-demand methods in a variety of field because it allows for the patterning of various ink. In addition, it can reduce the process time, cost and the toxic waste created during the manufacturing process. Also, this method can be easily applied to perform ink composition studies. Especially for fuel cell applications, inkjet printing resolves many of the problems associated with previous methods of catalyst deposition by allowing a uniform distribution of catalyst ink onto the surface of GDL or membrane and by loading a very low amount of catalyst.So in this research, in order to increase the performance of polymer electrolyte cells, the oxygen diffusion resistance was tested based on the difference of surface of catalyst layer in cathode by using inkjet method. Firstly, we mixed carbon supported Pt catalyst, distilled water and 20wt% Nafion solution and NPA together and then use homogenizer to disperse the liquid, then we got the catalyst ink. The Second step was fabrication of cathode catalyst layer (CCL) by using inkjet method. Third step was to observe the morphology for CCL with catalyst ink, in order to know the length and the height of a drop of ink, we made a sample, and then we took this sample to observe through laser microscope. When we got the basic information about morphology of CCL, we fabricated catalyst layer by inkjet, and took it to do the MEA evaluation and characterization to investigate their electrochemical properties, such as I-V curves, limiting current densities and impedance. And in order to compare with the experimental results, a theoretical model of the 3D structure was also circulated and discussed. From this model and measured data, it was confirmed that the better electrochemical properties results from 3D structure of catalyst layer in cathode.

Exploration of Photo and Electrochemical Studies with an Efficient Electrocatalyst on Fluorinated BiVO4 Photoelectrode for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting to produce clean hydrogen provides a desirable approach to solve the global environmental and energy problems. Bismuth vanadate (BiVO4) has emerged as one of the most promising photoanode materials for oxidizing water due to its visiblelight activity and low cost. However, BiVO4 photocatalyst has suffered by the slow charge separation kinetics at solid/electrode interface that limits the photoelectrochemical performance. In order to minimize the poor properties, we modified the BiVO4 with an effective electrocatalysts, which was investigated experimentally under light illumination. The subsequent addition of electrocatalysts as an effective oxygen evolution catalyst subsequently reduces the large overpotential and generates the higher photocurrent. The charge transfer properties of the photoelectrodes can be effectively tuned by controlling the electrocatalysts loaded, thereby optimizing PEC performance. Electrochemical impedance spectroscopy (EIS) evidenced that the deposition of electrocatalysts can substantially lower the charge transfer resistance at the semiconductor interface. Furthermore, the advantages and drawbacks of catalyst deposition routesand the role of photoelectrochemical and advanced spectroscopic techniques for elucidation of the mechanism of the photo catalytic action will be discussed in detail.

Understanding the Durability and Degradation of Gas Diffusion Electrodes for Carbon Dioxide Electrolysis in Alkaline Media

Anthropogenic CO2 emissions present an immediate and unprecedented threat to our planet. Electroreduction of CO2 (ECO2RR) offers the dual benefits of reducing CO2 emissions from point sources and producing valuable chemicals such as CO, formic acid, and ethanol in a carbon-neutral manner.1,2 Over the past decade, a significant body of research has focused on improving the product selectivity and activity of CO2RR catalysts, but studies regarding long-term stability and durability of these electrocatalytic systems have been rare.3 To date, only a few studies have reported performance durations exceeding 100 hours, and even fewer have reported on possible mechanisms underlying decrease in performance and system failure.4 Techno-economic analyses suggest a lifetime of 3000 hours or greater is needed for economically feasible ECO2RR systems5. Progress in this area will be crucial for further development of ECO2RR technology.This poster will report key findings from our comprehensive review of durability testing in ECO2RR systems, specifically common degradation mechanisms. We will focus primarily on gas diffusion electrodes (GDEs), used in high-performance alkaline flow and membrane electrode assembly systems. In our alkaline flow system, we have observed a number of degradation mechanisms consistently impacting our GDEs including leaching and carbonate formation. Characterization of used GDEs, including SEM, EDX, XRD, and Micro-CT, was employed to understand how operating at high current densities (–100 to –200 mA cm-2) in alkaline electrolytes impacts structure and chemical composition.Secondly, this poster will outline ways in which we have attempted to improve durability in our GDEs. By applying insights from the literature to studies carried out in our flow system, we have evaluated changes in the electrolyte, electrode substrate, catalyst deposition method, and catalyst ink binder to optimize GDE design and augment durability. Lastly, we will report on accelerated durability and stress testing (ADT/AST) methods that we have developed, and our findings from implementation of these methods in our system. These accelerated procedures can be broadly applied to highly active (≥200 mA cm–2), lab-scale ECO2RR systems to determine long-term stability and degradation modes in shorter timeframes. Acknowledgement We gratefully acknowledge financial support from Shell’s New Energies Research & Technology - Dense Energy Carriers Program and I2CNER.

Kinetic study of carbonaceous deposit formation and catalyst deactivation in hydrotreating of fast pyrolysis bio-oil

Fast pyrolysis of biomass followed by hydrotreating of bio-oil is considered to be a promising thermochemical conversion process of biomass to liquid fuel. Catalytic hydrotreating converts the crude bio-oil from biomass pyrolysis into liquid intermediates with reduced oxygen content, and low viscosity and acidity. However, effective lifetime of catalyst can be significantly reduced by coking which has been recognized as the main cause of catalyst deactivation during the hydrotreating process. In this study, similar phenomenon has been observed but the catalyst deposit was different from the reported coke and thus a new term of carbonaceous deposit is introduced. Kinetics of the carbonaceous deposit formation and its characteristics have been investigated for hydrotreating of bio-oil derived from fast pyrolysis of rice husk using commercial HTB-45 Ni-based catalyst. A mathematical model for the hydrotreating process, which is based on key chemical reactions and consists of ordinary differential equations (ODEs), has been developed and solved with the kinetic parameters being obtained from the experiments. Results of this study are helpful for better understanding and optimization of the catalytic upgrading of fast pyrolysis bio-oil.

The Controllable Design of Catalyst Inks to Enhance PEMFC Performance: A Review

Typical catalyst inks in proton exchange membrane fuel cells (PEMFCs) are composed of a catalyst, its support, an ionomer and a solvent and are used with solution processing approaches to manufacture conventional catalyst layers (CLs). Because of this, catalyst ink formulation and deposition processes are closely related to CL structure and performance. However, catalyst inks with ideal rheology and optimized electrochemical performances remain lacking in the large-scale application of PEMFCs. To address this, this review will summarize current progress in the formulation, characterization, modeling and deposition of catalyst inks. In addition, this review will highlight recent advancements in catalyst ink materials and discuss corresponding complex interactions. This review will also present various catalyst ink dispersion methods with insights into their stability and introduce the application of small-angle scattering and cryogenic transmission electron microscopy (cryo-TEM) technologies in the characterization of catalyst ink microstructures. Finally, recent studies in the kinetic modeling and deposition of catalyst inks will be analyzed. The formulation and the deposition process of catalyst inks determine the formation of catalyst. The interaction between the components of the catalyst ink governs the microstructure and processability of the ink, thereby affecting the microstructure and performance of the CL.

Effect of Ca Promoter on the Structure, Performance, and Carbon Deposition of Ni-Al2O3 Catalyst for CO2-CH4 Reforming.

Ni-Al2O3 catalyst with different Ca abundance for CO2-CH4 reforming was prepared by the solution combustion method. By some mature characterization methods, such as XRD, H2-TPR, EDX mapping, TEM, TPH and TG-DTG technologies, and the reforming experiment, the effect of Ca content on the structure, reforming performance, and carbon deposition of Ni-Al2O3 catalyst was investigated. Results showed that the grain size of active component Ni on the 4 wt % Ca-modified catalyst (Ni-Ca-4) was small (13.67 nm), presenting good dispersion, and that Ni and Ca elements were well distributed on the support, which was more conducive to the CO2-CH4 reforming. Evaluation results showed that activity of Ni-Ca-4 was higher than the others, with CH4 and CO2 conversions of 52.0 and 96.7%, respectively, and H2/CO ratio close to unit. Carbon deposition proposed that the amount of carbon deposited on the surface of Ni-Ca-4 was lower (18%), and the type of carbon was attributed to amorphous carbon, indicating that 4 wt % Ca-promoted catalyst presented better anticarbon deposition performance.

Catalytic Ozonation and Membrane Contactors—A Review Concerning Fouling Occurrence and Pollutant Removal

Membrane filtration has been widely used in water and wastewater treatment. However, this process is not very effective for the removal of refractory organic compounds (e.g., of pharmaceutical origin). Coupling membrane filtration with ozonation (or other Advanced Oxidation Methods) can enhance the degradation of these compounds and, subsequently, the incidence of membrane fouling (i.e., the major problem of membrane uses) would be also limited. Ozonation is an efficient oxidative process, although ozone is considered to be a rather selective oxidant agent and sometimes it presents quite low mineralization rates. An improvement of this advanced oxidation process is catalytic ozonation, which can decrease the by-product formation via the acceleration of hydroxyl radicals production. The hydroxyl radicals are unselective oxidative species, presenting high reaction constants with organic compounds. An efficient way to couple membrane filtration with catalytic ozonation is the deposition of an appropriate solid catalyst onto the membrane surface. However, it must be noted that only metal oxides have been used as catalysts in this process, while the membrane material can be of either polymeric or ceramic origin. The relevant studies regarding the application of polymeric membranes are rather scarce, because only a few polymeric materials can be ozone-resistant and the deposition of metal oxides on their surface presents several difficulties (e.g., affinity etc.). The respective literature about catalytic membrane ozonation is quite limited; however, some studies have been performed concerning membrane fouling and the degradation of micropollutants, which will be presented in this review. From the relevant results it seems that this hybrid process can be an efficient technology both for the reduction of fouling occurrence as well as of enhancement of micropollutant removal, when compared to the application of single filtration or ozonation.

SO2-Tolerant NOx Reduction by Marvelously Suppressing SO2 Adsorption over FeδCe1-δVO4 Catalysts.

SO2-tolerant selective catalytic reduction (SCR) of NOx at low temperature is still challenging. Traditional metal oxide catalysts are prone to be sulfated and the as-formed sulfates are difficult to decompose. In this study, we discovered that SO2 adsorption could be largely restrained over FeδCe1-δVO4 catalysts, which effectively restrained the deposition of sulfate species and endowed catalysts with strong SO2 tolerance at an extremely low temperature of 240 °C. The increasing oxygen vacancies, enhanced redox properties, and improved acidity contributed to the SCR activity of the FeδCe1-δVO4 catalyst. The reaction pathway changed from the reaction between bidentate nitrate and the NH3 species over CeVO4 catalysts via the Langmuir-Hinshelwood mechanism to that between gaseous NOx and the NH4+/NH3 species over FeδCe1-δVO4 catalysts via the Eley-Rideal mechanism. The effective suppression of SO2 adsorption allowed FeδCe1-δVO4 catalysts to maintain the Eley-Rideal pathways on account of the reduced formation of sulfate species. This work demonstrated an effective route to improve SO2 tolerance via modulating SO2 adsorption on Ce-based vanadate catalysts, which presented a new point for the development of high-performance SO2-tolerant SCR catalysts.

Electrochemical Deposition of PdBiSn Catalyst for Glycerol Oxidation in Alkaline Medium

AbstractPdBiSn thin film on Au substrate was prepared by means of the electrochemical atomic layer deposition (E‐ALD) technique. The morphology and elemental distribution of the catalysts was determined using scanning electron microscope equipped with energy dispersive spectroscopy (EDS) detector. The catalysts contained all the deposited elements distributed evenly on the surface. Electro‐oxidation of glycerol was tested in alkaline media using cyclic voltammetry (CV) and chronoamperometry (CA). The activity of the catalysts towards the oxidation of glycerol improved with the addition of Sn and Bi with the binary PdBi catalyst being the most improved.

Nanostructured Boron Doped Diamond Electrodes with Increased Reactivity for Solar‐Driven CO2 Reduction in Room Temperature Ionic Liquids

AbstractConductive, boron doped diamond (BDD) is an extraordinary material with many applications in electrochemistry due to its wide potential window, outstanding robustness, low capacitance and resistance to fouling. However, in photoelectrochemistry, BDD usually requires UV light for excitation, which impedes e. g., usage in CO2 to fuel reduction. In this work, a heavily boron doped, nanostructured diamond electrode with enhanced light absorption has been developed. It is manufactured from BDD by reactive ion etching and presents a coral‐like structure with pore diameters in the nanometer range, ensuring a huge surface area. The strong light absorbance of this material is clearly visible from its black color. Consequently, the material is called Diamond Black (DB). Electrochemical and X‐ray photoelectron spectroscopy measurements performed at near‐ambient pressure conditions of water vapor demonstrate increased surface reactivity for the hydrogen‐terminated DB compared to oxidized surfaces. Depending on the surface termination, the wettability and hence the electrochemically accessible area can be changed. Photoelectrochemical conversion of CO2 was demonstrated using a Cu2O‐modified electrode in ionic liquids under solar illumination. High formic acid production rates at low catalyst deposition times can be obtained paired with an increased catalyst stability on the DB surface.

Microfluidic, One-Batch Synthesis of Pd Nanocrystals on N-Doped Carbon in Surfactant-Free Deep Eutectic Solvents for Formic Acid Electrochemical Oxidation.

One of the grand challenges that impedes practical applications of nanomaterials is the lack of robust manufacturing methods that are scalable, cheap, and environmentally friendly. Herein, we address this challenge by developing a microfluidic approach that produces surfactant-free Pd nanocrystals (NCs) uniformly loaded on N-doped porous carbon in a one-batch process. The deep eutectic solvent (DES) prepared from choline chloride and ethylene glycol was employed as a novel synthesis solvent, and its extended hydrogen networks and abundant ionic species effectively stabilize Pd facets and confine nanocrystal sizes without using surfactants. The microreactors provide faster heat exchange and more uniform mass transport, which in combination with DES produced Pd NCs with better-defined shape and predominately exposed Pd (100) facet. Furthermore, we describe that the N-doped functional groups in porous carbon direct dense and uniform heterogeneous growth of Pd NCs in a one-batch process, thereby eliminating a separate catalyst deposition step that is often involved in conventional synthesis. The Pd NCs in the one-batch-produced Pd/C catalysts exhibited a size distribution of ∼13 ± 3.5 nm and a high ESCA of 46.0 m2/g and delivered 362 mA/mg for formic acid electrochemical oxidation with improved stability, demonstrating the unique potentials of microfluidic reactors and DES for the controllable and scalable synthesis of electrocatalyst materials for practical applications.