Catalyst Particle Size Distribution Research Articles

Fluidized-bed OCM reaction: A promising Mn2O3-Na2WO4/TiO2 catalyst and a numerical study

The fluidized-bed reactor with excellent heat and mass transfer features has great appeal for application in the oxidative coupling of methane (FB-OCM), whereas qualified fluid catalysts represent a grand challenge. Herein, we report a high-performance Mn2O3-Na2WO4/TiO2 fluid catalyst (5.4 wt% Mn2O3 and 2 wt% Na2WO4), which was obtained by the incipient-wetness impregnation method and examined in the OCM reaction in an electric-heating quartz fluidized-bed reactor (i.d., 2 cm). The standard normalization method on the basis of carbon atom was used for calculating the CH4 conversion and C2-C3 selectivity. This catalyst achieves 35.5 % CH4 conversion, 66 % C2-C3 selectivity and particularly 15.1 % single-pass yield of C2H4 for a feed of CH4/O2/H2O=3/1/1 with a catalyst dosage of 20 mL at 700 °C and a total GHSV of 7200 h−1. Such catalyst is stable for at least 50 h without signs of deactivation and agglomeration/defluidization. The catalyst particle size is crucial for the FB-OCM reaction with respect to the reaction light-off and catalyst fluidization. The catalyst with preferable particle size of 450–600 μm can not only trigger the OCM reaction at a relatively low temperature of 630 °C but also warrant active bubbling fluidization. Furthermore, thanks to the low amount of Na2WO4 and interpenetrating structure of TiO2-nanorod, such catalyst achieves good anti-aggregation and robust mechanical strength (with a low attrition index of 1.9 %). The effects of water-adding amount in feedstock and catalyst particle size distribution on the hydrodynamics behaviour were investigated in a laboratory-scale fluidized-bed OCM reactor by using numerical simulation method.

Promoting AEM Water Electrolyzer Performance and Reproducibility by Tumbler Milling of Ni3fe-LDH OER Catalyst

Anion exchange membrane water electrolysis is an attractive clean energy technology for producing hydrogen for energy storage, transport 1,2 and numerous other applications. Rational choice of highly active and stable catalysts as well as the proper design of catalyst layers are crucial to achieve technical relevance of electrolyser systems. The establishment of clear understanding of optimal catalyst treatment and methods of implementation are key steps towards optimized electrolyzer performance and durability. One aspect of catalyst performance in catalyst layers is the catalyst size distribution. A multimodal size distribution of catalyst particles or agglomerates can jeopardize the layer homogeneity and thus electrode performance.In this work, the effect of high-energy ball tumbling milling on the promising Ni3Fe-LDH OER catalyst followed by catalyst dispersion control was correlated to the microstructure of the catalyst layer, the achieved catalyst activity and utilization, and the resulting single cell performance and stability. Physico-chemical characterization confirmed the stable layered double hydroxide structure of the catalyst. By milling, a 300-fold reduction of catalyst agglomerate size, and an 8.8-fold increase of the geometrical surface was achieved. The optimized solvent compositions effectively increased the catalyst ink stability. We found that a significantly decreased catalyst agglomerate size resulted in very homogeneous mixtures of catalyst and ionomer. By tailoring the electrode structure design, lower internal electronic resistances of the electrodes, decreased charge-transfer resistances (Rct) of the membrane electrode assembly, and stable single cell durability of 1000 h with a minor degradation rate of 57 µV h-1 were accomplished.This work presents a facile and scalable approach of NiFe-LDH catalyst treatment and dispersion control and provides a guideline to follow for further electrode development and increased AEM water electrolyzer performances. References (1) Hydrogen Applications. Hydrogen Europe. 2020. https://hydrogeneurope.eu/hydrogen-applications (accessed Jan 7, 2022).(2) Vincent, I.; Bessarabov, D. Low Cost Hydrogen Production by Anion Exchange Membrane Electrolysis: A Review. Renew. Sustain. Energy Rev. 2018, 81 (August 2016), 1690–1704. https://doi.org/10.1016/j.rser.2017.05.258. This work has been performed in the frame of the CHANNEL project. This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under grant agreement No 875088. This Joint undertaking receives support from the European Union's Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research.

Precisely identify the geometry of catalyst particles from S/TEM images via a boundary attention deep learning network

The size and shape of the nanoparticles have a great impact on their performances as catalysts. Traditional method of manually measuring particles from scanning/transmission electron microscopy (S/TEM) images has limited counting ability of only up to hundreds of particles, not enough to support an accurate statistic and besides, the one dimensional (1D) manual measurement by drawing a line across nanoparticles would induce large bias given the practical supported catalysts whose particles always present irregular geometry. To develop an automatic and precise recognition method based on TEM data has been a long-standing demand to facilitate a highly efficient catalytic dispersion evaluation. In this paper, we propose an end-to-end boundary attention deep learning network to recognize nanoparticles in S/TEM images. The proposed model is an extension of the U-Net embedding a residual boundary attention module to extract the edge information of catalyst particles and a fusion module to exploit the edge features, gradient features and the results out from decoder to enhance recognition performance. Results demonstrate that the proposed boundary attention structure is superior to well-accepted U-Net framework in dealing with the precise particle recognition. Using our new method, a particle size distribution of PdCu catalyst at statistic scale of 14,000 + is achieved, through which more reliable and accurate results of S/TEM characterization can be obtained to facilitate efficient and reliable evaluation of catalysts dispersion.

Development of an Integrated Framework for Multiscale, Multiphase Modeling of Industrial Slurry‐Phase Reactors for Polyethylene Production

AbstractA framework based on the Monte Carlo/random‐pore polymeric flow model is proposed to simulate both single‐particle and continuous slurry reactor industrial polymerizations. The Sanchez–Lacombe equation of state describes the distributions of components in the different phases of these systems. The developed process model is applied to describe heterogeneously catalyzed polymerizations of ethylene in n‐hexane diluent with or without 1‐hexene as a comonomer, but the proposed methodology is applicable to any ethylene/1‐olefin copolymerization in slurry reactors. In addition to the effects of catalyst particle size and reactor residence time distributions, the proposed hybrid model is used to investigate the impact of several catalyst characteristics under different process conditions on polymer yield and microstructure. Particular attention is paid to the catalyst fragmentation process and active center distribution through the particle. These simulations demonstrate the versatility and thoroughness of combining Monte Carlo simulation with single‐particle models to analyze and predict the behavior of commercial polyolefin reactors.

Non-uniform size of catalyst particles. Impact on the effectiveness factor and the determination of kinetic parameters

The analysis of the effectiveness factor in catalytic particles with non-uniform size, was performed. The procedure proposed by Weisz and Prater to determine the intrinsic kinetic constants from experimental results was extended to cases where the catalyst particle size distribution is considered. The approach was applied to the study of reactions with power law and Langmuir-Hinshelwood-Hougen-Watson type kinetics, the catalyst particles being spheres with volume log-normal size distribution (typical in, e.g., fluid catalytic cracking catalysts). If the catalytic effectiveness factor is calculated assuming uniform particle size Rm (Rm being the volume to area mean radius), it will be always higher than the actual effectiveness factor. If the particle size distribution is not taken into account during the assessment of the intrinsic kinetic constants by means of the Weisz and Prater method, the values of those constants will be erroneous. The higher the dispersion in the particles size distribution, the higher the error in ignoring the impact of the different sizes.

Study on Friction Sensitivity of Passive and Active Binder based Composite Solid Propellants and Correlation with Burning Rate


 Friction sensitivity of composite propellants and their ingredients is of significant interest to mitigate the risk associated with the accidental initiation while processing, handling, and transportation. In this work, attempts were made to examine the friction sensitivity of passive binder: Hydroxy Terminated Polybutadiene/Aluminium/Ammonium Perchlorate and active binder: (Polymer + Nitrate Esters)/Ammonium Perchlorate/Aluminium/Nitramine based composite propellants by using BAM Friction Apparatus. As per the recommendation of NATO standard STANAG–4487, the friction sensitivity was assessed by two methods: Limiting Frictional load and Frictional load for 50% probability of initiation (F50). The test results showed that the active binder based formulations were more vulnerable to frictional load as compared to the formulations with passive binders. Examination of a comprehensive set of propellant compositions revealed that the particle size distribution of Ammonium Perchlorate and burn rate catalysts were the most influential factors in dictating the friction sensitivity for HTPB/Al/AP composite propellants. For active binder/AP/Al/Nitramine composite propellants, the formulation with RDX was found more friction sensitive with a sensitivity value of 44 N as compared to its HMX analog (61 N). The correlation studies of friction sensitivity, burning rate, and thermal decomposition characteristics of HTPB/Al/AP composite propellants is described.

Systematic investigation of the catalyst composition effects on single-walled carbon nanotubes synthesis in floating-catalyst CVD

Enormous technological promise of single-walled carbon nanotubes (SWCNTs) can only be harnessed with the premise of controllable synthesis of SWCNTs, where catalyst composition thermodynamically plays a vital role. Herein, we have systematically investigated the effects of catalyst composition on SWCNTs synthesis, using a novel floating-catalyst chemical vapor deposition (FCCVD) system, consisting of catalyst synthesis via spark generator, FCCVD reactor and a real-time monitor of catalysts and SWCNTs. We synthesized SWCNTs from both monometallic (Fe, Co, Ni), bimetallic (Co-Ni, Co-Fe) catalyst particles and kinetically optimized yield and performance of SWCNTs films. We found that the highest yield of SWCNTs from Fe is 15 times as that of Ni SWCNTs and the Co-Ni SWCNTs film possesses best opto-electronic performance. Interestingly, the mean diameter of SWCNTs was found related to the catalyst particle size distributions, but not composition. Moreover, detailed atomic structures determination revealed that SWCNTs from Fe and Co have a wide chirality distribution spanning from zig-zag to armchair edges. However, Co-Ni SWCNTs have comparatively narrower chirality distribution having 71% SWCNTs in the chiral angle of 15–30°. Our results indicate that catalyst composition can efficiently tune yield and characteristics of SWCNTs, but it does not dramatically shift chirality of FCCVD SWCNTs.

Pulsed Electrodeposition of Gas-Diffusion Electrocatalysts for CO2 Reduction

The performance of electrocatalysts for the electrochemical carbon dioxide (CO2) reduction reaction (eCO2RR) is largely dependent on the ability to efficiently deliver CO2 to the active sites. A variety of reactor configurations have been explored in the literature that can be broadly classified as based on either liquid- or gas-phase reactant delivery. These configurations utilize a range of electrode types including metal plates, meshes, packed granules, and gas diffusion electrodes (GDEs) [1]. Amongst these methods, the use of gas-phase reactor designs employing GDEs enables a dramatic increase in current density (typically an order of magnitude or larger) over liquid-phase reactor designs, where the low solubility and aqueous diffusivity of CO2 result in severe mass transport limitations. However, the performance of GDEs in various CO2 electroreduction processes can be hampered by poor catalyst utilization and transport limitations within the catalyst layer. At higher catalyst loadings (thicker catalyst layers), which are desirable for high production rates, conversion efficiencies drop and undesirable side product formation (both from hydrogen evolution and diversion of carbon to alternative reaction pathways) increases due to reactant starvation. Reducing particle size typically enhances both catalyst utilization and activity per unit mass. This, in turn, may enable thinner catalyst layers, mitigating or avoiding such decreases in product selectivity. While synthesis methods exist for generating smaller (< 10 nm) particles, these particles must still be deposited on a gas-diffusion layer (GDL) substrate such that ionic and electronic contact can be maintained with the electrolyte and GDL, respectively. Previous work directed towards platinum (Pt) catalyst utilization in polymer electrolyte fuel cell GDEs demonstrated an “electrocatalyzation” (EC) approach that used pulse and pulse-reverse electrodeposition to obtain highly dispersed and uniform Pt catalyst nanoparticles (~5 nm) [2-4]. Moreover, since the catalyst was electroplated through an ionomer layer onto the bare GDL, the formed nanoparticles were inherently in both electronic and ionic contact within the GDE and, consequently, utilization was enhanced (see Figure - Schematic comparison of catalyst particle size and location distributions in conventional spray-painting versus electrodeposition application methods). Specifically, for the oxygen reduction reaction, the electrodeposited catalyst exhibited equivalent performance at 0.05 mg/cm2 loading compared to a conventionally prepared GDE with a loading of 0.5 mg/cm2 [4]. This talk will discuss the electrodeposition of tin (Sn) and copper (Cu) onto both commercially-available and custom-fabricated GDLs through an EC process, and the electrocatalysis performance of these catalysts as compared to state-of-the-art Sn and Cu nanoparticle catalysts (75-150 nm) prepared by spray-coating. Testing in a custom flow-cell electroreactor has demonstrated that the EC GDEs exhibit electrocatalytic performance comparable or superior to both literature reports and the spray-painted catalysts. Further, clear effects of the pulsed-waveform EC parameters on product distribution and total current density will be highlighted. Preliminary work toward development of GDLs robust against electrolyte saturation/penetration over many hours of operation will also be discussed. In summary, the highly scalable EC approach appears promising for fabricating active catalytic layers directly onto GDL substrates for carbon dioxide reduction applications.

High performance gas-phase ethylene polymerization metallocene catalyst investigation in a pilot-plant fluidized bed reactor (1) experimental analysis

This work aims to explore the scaling up process of lab developed heterogeneous metallocene catalyst in a pilot-plant scale fluidized bed reactor in comparison of benchmark catalyst producing polyethylene. The catalyst performance has been evaluated through copolymerization behaviors and polymerization kinetics. The produced polymers are analyzed in revealing the scale up effect of the catalyst. It was found that the catalyst particle size distribution shows very similar size distribution compared to the industrial catalyst and good particle morphology, which will benefit the gas phase fluidized bed operation. Compared to the benchmark HP-100, PME-18 shows better catalytic parameters in the ethylene/1-hexene polymerization behavior and reaction kinetics. The final product demonstrates very similar particle size distribution and polymer properties, which will obviously influence the product quality and production state.

Diameter controlled growth of SWCNTs using Ru as catalyst precursors coupled with atomic hydrogen treatment

In this work, we present a practical approach for controlling single walled carbon nanotubes (SWCNTs) diameter distribution through thin film Ru catalyst, coupled with hydrogen pre-treatment. Uniform and stable Ru nanoclusters were obtained after dewetting the Ru thin films under atomic hydrogen pre-treatment. SWCNTs were synthetized by double hot filament chemical vapor deposition (d-HFCVD) on SiO2/Si substrates at different temperatures. We found that the temperature is an important synthesis parameter that influences the diameter distribution of the final SWCNTs. Statistical analysis of the Raman radial breathing modes evidences the growth of highly enriched semi-conducting SWCNTs (about 90%) with narrow diameter distribution that correlates directly with the catalyst particle size distribution. Electrical measurement results on as-grown SWCNTs show good thin-film transistor characteristics.

Evolution of implanted Fe ions in SiO2/Si wafer into uniformly sized catalyst particles for carbon nanotube forest growth

We report the synthesis of carbon nanotube (CNT) forests with a narrow diameter distribution based on Fe ion implantation method. By annealing the Fe-implanted SiO2/Si wafer in an Ar atmosphere at 800 °C for 15 min, the Fe particles on the surface of SiO2 layer are successfully formed by the diffusion of Fe atoms from the SiO2 layer. Interestingly, the size distribution of Fe catalyst particles for Fe-implanted SiO2/Si wafers does not change with the prolonged annealing durations of up to 12 h. Using secondary ion mass spectroscopy and transmission electron microscopy (TEM), we confirmed that the implanted Fe atoms diffuse out of the SiO2 layer and form Fe particles on both the SiO2 surface and the interface between SiO2 and Si. The cross-sectional TEM images indicate that the Fe catalyst particles are anchored in the SiO2 layer, which limits the particles' mobility and results in an invariant catalyst size distribution for prolonged annealing durations. Therefore, we anticipate that implantation can be an efficient alternative catalyst preparation method for CNT forest growth which can solve various growth issues that are inherently caused by conventional physical vapor deposition method.

Plasma-Assisted Dispersion of Bimetallic Ni–Co over Al2O3–ZrO2 for CO2 Reforming of Methane: Influence of Voltage on Catalytic Properties

Glow discharge plasma with different voltages (700, 1000 and 1300 V) has been applied for treatment of Ni–Co/Al2O3–ZrO2 catalyst. Physicochemical properties of the catalysts were investigated by XRD, FESEM, BET and FTIR. Based on characterization results, there was an optimum amount of voltage (1000 V) in which the most uniform morphology, highest surface area and the smallest particle size was observed. On contrary of two other catalysts, 1000 V-treated Ni–Co/Al2O3–ZrO2 catalyst showed amorphous structure for NiO which led to improved dispersion of active phase and strong metal–support interactions. In this catalyst particle size distribution was narrow and average particle size was reported to be 21.2 nm. Dry reforming of methane to syngas using synthesized Ni–Co/Al2O3–ZrO2 nanocatalysts illustrated highest catalyst reactivity in the case of 1000 V-treated Ni–Co/Al2O3–ZrO2 nanocatalyst. This catalyst exhibited 99% feed conversion while 700 and 1300 V-treated catalysts showed 91 and 95% feed conversions at 850 °C, respectively. The H2/CO ratio over 700, 1000 and 1300 V treated catalysts was 0.83, 0.98 and 0.88, respectively.

Unveiling the Evolutions of Nanotube Diameter Distribution during the Growth of Single-Walled Carbon Nanotubes.

In situ and ex situ Raman measurements were used to study the dynamics of the populations of single-walled carbon nanotubes (SWCNTs) during their catalytic growth by chemical vapor deposition. Our study reveals that the nanotube diameter distribution strongly evolves during SWCNT growth but in dissimilar ways depending on the growth conditions. We notably show that high selectivity can be obtained using short or moderate growth times. High-resolution transmission electron microscopy observations support that Ostwald ripening is the key process driving these seemingly contradictory results by regulating the size distribution and lifetime of the active catalyst particles. Ostwald ripening appears as the main termination mechanism for the smallest diameter tubes, whereas carbon poisoning dominates for the largest ones. By unveiling the key concept of dynamic competition between nanotube growth and catalyst ripening, we show that time can be used as an active parameter to control the growth selectivity of carbon nanotubes and other 1D systems.

Carbonaceous deposition onto the outer surface of vortex finder of commercial RFCC cyclones and role of gas flow to the buildup of the deposits

Unwanted build-up of carbonaceous deposits on RFCC equipment surface is a key process limitation to achieving the economic benefits of longer run length. This paper focuses on the carbonaceous deposition on the outer surface of vortex finder of secondary cyclone. Macroscopic features of industrial deposits are reported in detail. Extensive characterization studies such as elemental analysis, scanning electron microscopy, energy dispersive spectrometry, thermal behavior were conducted and size distribution of catalyst particles in deposits was measured. Computational fluid dynamics method was used to obtain the gas flow field around the vortex finder. The role of gas flow to the buildup of deposits was discussed. The results will provide comprehensive understanding of deposit formation and insight into the process and operation improvement.

Obtainment of Sorbitol on Ferroalloy Promoted Nickel Catalysts

The systematic study of the activity of the catalyst suspended with ferroalloys additives in catalytic hydrogenation of glucose over a wide variation of process parameters is given in this article. Since nickel catalysts were studied sufficiently, we limited to the data of the phase composition and structure; specific surface of alloys and catalysts based on aluminum-nickel alloys, modified ferroalloys. Results of the study of phase, chemical, particle size distribution and structure of nickel alloys and catalysts have shown that modifying metals affect to the ratio of NiAl3/Ni2Al3 in the alloys, crush crystals, increase catalyst particle size, surface area and large size pore volume and simultaneously increase the micro- and supermicro pore ratio. Highly active, stable and selective catalysts based on nickel for the sorbitol synthesis process was developed.

Catalyst nanoparticle growth dynamics and their influence on product morphology in a CVD process for continuous carbon nanotube synthesis

Extrapolating the properties of individual CNTs into macro-scale CNT materials using a continuous and cost effective process offers enormous potential for a variety of applications. The floating catalyst chemical vapor deposition (FCCVD) method discussed in this paper bridges the gap between generating nano- and macro-scale CNT material and has already been adopted by industry for exploitation. A deep understanding of the phenomena occurring within the FCCVD reactor is thereby key to producing the desired CNT product and successfully scaling up the process further. This paper correlates information on decomposition of reactants, axial catalyst nanoparticle dynamics and the morphology of the resultant CNTs and shows how these are strongly related to the temperature and chemical availability within the reactor. For the first time, in-situ measurements of catalyst particle size distributions coupled with reactant decomposition profiles and a detailed axial SEM study of formed CNT materials reveal specific domains that have important implications for scale-up. A novel observation is the formation, disappearance and reformation of catalyst nanoparticles along the reactor axis, caused by their evaporation and re-condensation and mapping of different CNT morphologies as a result of this process.

Controlling the diameter of aligned single-walled carbon nanotubes on quartz via catalyst reduction time

One of the main objectives of chemical vapor deposition (CVD) growth of single-walled carbon nanotubes (SWCNT) is control over their diameter and type (metallic or semiconducting). Here, we investigate the evolution of iron catalyst particles on quartz substrates depending on the duration of the reduction step with hydrogen and its effect on the growth of horizontally aligned SWCNT. We find a strong dependence of catalyst particle size and size distribution on the initial iron film thickness and the reduction time at 630 °C. Initial decrease of the particle size is followed by an unexpected increase. Statistical analysis of the Raman radial breathing modes of the SWCNT over large areas gave reliable and reproducible diameter distributions that correlated directly with the catalyst particle size distributions. By changing the reduction time it was possible to reproducibly shift the average SWCNT diameter from 1.5 (±0.3) nm to 1.2 (±0.2) nm while maintaining a nanotube density of 5–6 SWCNT/μm. In order to describe the evolution of the particle size during the reduction process at this particular temperature, we propose a model that includes the diffusion of iron into the quartz and its re-emergence.

Effective Strategy for Improving Electrocatalyst Durability by Adhesive Immobilization of Catalyst Nanoparticles on Graphitic Carbon Supports

We have found that Ta-based additive films in our catalyst system act as adhesives, which improves electrocatalyst durability by immobilizing the catalyst Pt NPs on the graphitic Vulcan carbon support. Furthermore, we suggest that this can be a general design principle in producing higher-durability electrocatalysts on graphitic supports. By electrochemically probing the contributing roles of the tantalum oxide (Ta2O5) and the polyphosphate (PPA) components in separate samples, we show that these combine to produce the observed improvement in activity and durability of our best catalyst, the tantalum polyphosphate (TaOPO4)-treated sample. To control variables for a valid electrochemical comparison, such as dissimilar catalyst particle size distributions and variations in surface coverage, four new catalyst samples closely matched in every way were prepared: (1) Pt/VC, (2) Pt/[PPA/VC], (3) Pt/[Ta2O5/VC], and (4) Pt[TaOPO4/VC]. We present HR-TEM/HAADF-STEM, EDS elemental mapping, PXRD, XPS, and electrochemi...

A RhxSy/C Catalyst for the Hydrogen Oxidation and Hydrogen Evolution Reactions in HBr

Rhodium sulfide (Rh2S3) on carbon support was synthesized by refluxing rhodium chloride with ammonium thiosulfate. Thermal treatment of Rh2S3 at high temperatures (600°C to 850°C) in presence of argon resulted in the transformation of Rh2S3 into Rh3S4, Rh17S15 and Rh which were characterized by TGA/DTA, XRD, EDX, and deconvolved XPS analyses. The catalyst particle size distribution ranged from 3 to 12 nm. Cyclic voltammetry and rotating disk electrode measurements were used to evaluate the catalytic activity for hydrogen oxidation and evolution reactions in H2SO4 and HBr solutions. The thermally treated catalysts show high activity for the hydrogen reactions. The exchange current densities (io) of the synthesized RhxSy catalysts in H2-saturated 1M H2SO4 and 1M HBr for HER and HOR were 0.9 mA/cm2 to 1.0 mA/cm2 and 0.8 to 0.9 mA/cm2, respectively. The lower io values obtained in 1M HBr solution compared to in H2SO4 might be due to the adsorption of Br− on the active surface. Stable electrochemical active surface area (ECSA) of RhxSy catalyst was obtained for CV scan limits between 0 V and 0.65 V vs. RHE. Scans with upper voltage limit beyond 0.65 V led to decreased and unreproducible ECSA measurements.

Synthesis and Characterization of RhxSy/C Catalysts for HOR/HER in HBr

Rhodium sulfide on carbon support (denoted as Rh2S3/C) was synthesized by refluxing of rhodium chloride (RhCl3) with ammonium thiosulfate. By thermal treatment in Ar, Rh2S3 can be transformed into different phases, such as Rh17S15, Rh3S4 and Rh, which were evident from XRD analysis. The particle size distribution of catalysts with the range from 3 to 12 nm (average 6 nm) was observed by transmission electron microscopy (TEM). The activity in terms of exchange current density (i 0) for hydrogen oxidation (HOR) and hydrogen evaluation (HER) reaction in H2-saturated 1M hydrobromic acid (HBr) solution was obtained from the slope of Butler-Volmer plots.