Catalyst In Acidic Medium Research Articles

Fe2O3@FeP core-shell nanocubes/C composites supported irregular PtP nanocrystals for enhanced catalytic methanol oxidation

The construction of highly active Pt-based catalyst for methanol electrooxidation is still an ongoing challenge. Herein, irregular PtP nanocrystals with the length is around 7 nm supported on the Fe2O3@FeP/C composites consisting of Fe2O3@FeP core-shell nanocubes and carbon black particles are synthesized by an integrated hydrothermal, low temperature phosphidation and NaBH4 reduction process. TEM and EDS reveal that both the presence of phosphorus (P) and the mild Pt reduction method are play a critical role in constructing irregular PtP nanocrystals. Interestingly enough, the confinement effect of carbon particles on iron ions in the process of hydrothermal reaction leads to the generation of Fe-precursor nanocubes. Benefiting from the P can effectively modify the electronic state of the Pt surface, the strong interaction between special irregular PtP nanocrystals and the support surface as well as Fe2O3@FeP core-shell nanocubes for the enhanced activation and decomposition of H2O molecules, the as-prepared PtP-Fe2O3@FeP/C-8 h catalyst exhibits better anti-CO poisoning ability, stability and excellent catalytic activity for methanol oxidation. Specifically, the mass activity (831 mA mg−1Pt) of PtP-Fe2O3@FeP/C-8 h is 4.6- and 2.1-times greater than that of home-made Pt/C (Pt/C-H) (180 mA mg−1Pt) and commercial Pt/C (Pt/C-JM) (393 mA mg−1Pt) catalyst in acidic medium. At the same time, the mass activity of PtP-Fe2O3@FeP/C-8 h is as high as 3215 mA mg−1Pt, which is much higher than those of Pt/C-H (1298 mA mg−1Pt) and Pt/C-JM (1548 mA mg−1Pt) catalysts in alkaline medium. The present work provides a new entry points into the synthetic way for the irregular PtP nanocrystals and cheap co-catalytic species for methanol oxidation reaction (MOR).

Molecular-Level Design and Synthesis of M-N-C Non-Precious Metal Catalysts Derived from Transition Metal-Coordinated Bis(imino)-Pyridine Based Polymers for Highly Efficient Oxygen Reduction

Molecular-Level Design and Synthesis of M-N-C Non-Precious Metal Catalysts Derived from Transition Metal-Coordinated Bis(imino)-Pyridine Based Polymers for Highly Efficient Oxygen ReductionZhi Qun Tian*, Xiaoran Zhang, Dandan Lyu, and Pei Kang Shen Collaborative Innovation Center of Sustainable Energy Materials, Guangxi Key Laboratory of Electrochemical Energy Materials, State Key Laboratory of Processing for Non-ferrous Metal and Featured Materials, Guangxi University, Nanning，53004, China. （E-mail:tianzhiqun@gxu.edu.cn）: Transition-nitrogen-carbon (M-N-C) materials as the most promising non-precious metal catalysts for oxygen reduction reaction (ORR) to replace Pt-based catalysts are in high demand for large scale application of fuel cells. However, their activity and durability are still critical issues. Development of M/N/C-containing precursors is a straightforward strategy for obtaining advanced M-N-C ORR catalysts to address these issues. Herein, we report a new strategy for synthesizing a highly efficient and robust M-N-C catalyst for oxygen reduction reaction (ORR) via the pyrolysis of bis(imino)-pyridine metal-ligand based polymers. A series of Fe-N-C, Co-N-C and Mn-N-C catalysts prepared by the new presucors displays an excellent electrochemical performance for ORR with onset and half-wave potentials of >0.95 V, 0.84 V vs. RHE, respectively, in acidic media, and >1.0 V, 0.9 V vs. RHE, respectively, in alkaline media. These values are comparable to commercial Pt/C catalyst in acidic media and even more superior to commercial Pt/C in alkaline media. And a low H2O2 yield (< 2%) in the diffusion-limiting current region and a high electron transfer number (3.97-3.99) were achieved in our catalysts, indicating the occurance of direct 4 e- process for ORR. Meanwhile, the catalyst shows remarkable cycle stability at high potential range of 0.6-1.35V both in alkaline and acidic media, outperforming Fe-N-C catalysts reported previously, which is important for practical application of ORR catalysts in fuel cells. This feature makes it among most efficient non-precious catalysts in alkaline/acidic media for ORR. We believe this novel approach may open a new way of synthesizing highly efficient and robust noble metal-free catalysts for ORR.

Iron and Nitrogen Doped Carbide Derived Carbon and Composite Catalysts for Fuel Cell Cathodes

Producing renewable energy is one of the most important electrochemical challenges in the 21st century. Currently the focus is mainly on enhancing the oxygen reduction reaction (ORR) on the cathode of the fuel cell and to utilize non-noble metal catalysts instead of the expensive and scarce Pt-based catalysts that are currently prevalent. Iron and nitrogen doped nanocarbons have emerged as a possible replacement. Here, we study a catalyst material synthesized from carbide-derived carbon (CDC, a carbon material made by removing the metal atoms from a carbide) and composites of CDC and carbon nanotubes (CNT). To dope this material, 1,10-phenanthroline and iron(II)acetate were used in a ball-milling and pyrolysis procedure.1,2 The composites were created by adding CNTs, dicyandiamide and additional iron(II)acetate before repeating the ball-milling and pyrolysis process. The surface morphology was examined by scanning electron microscopy (SEM), and elemental composition by X-ray photoelectron spectroscopy (XPS), porosity analysis was done by N2 adsorption/desorption and the bulk elemental composition was studied by inductively coupled plasma mass spectroscopy (ICP-MS). The speciation of iron was studied using 57Fe Mössbauer spectroscopy. These CDC-based Fe-N-C catalysts show promising half-wave potential for ORR of 0.81 V vs RHE in 0.5 M H2SO4. For a same Fe content of 0.5 wt% in the catalyst precursor, the Fe-N-C catalyst derived from CDC-2 (derived from TiC) showed ca. 5 times higher activity at 0.8 V vs. RHE than that derived from CDC-1 (derived from B4C). The residual presence of boron in CDC-1 seems to be the main reason for the lower activity of CDC-1 derived catalysts, leading to the preferential formation of iron boride instead of ORR-active FeNxCy moieties. Higher Fe contents were investigated for CDC-2, but lead to unmodified activity, which is explained from Mössbauer spectroscopy measurements by the increasing formation of ORR-inactive Fe species at high Fe content. The addition of CNTs to create a core-shell composite with a CNT shell surrounding the CDC cores increased the stability of the catalyst in acidic media. Figure 1

Quadruple perovskite ruthenate as a highly efficient catalyst for acidic water oxidation

Development of highly active and durable oxygen-evolving catalysts in acid media is a major challenge to design proton exchange membrane water electrolysis for producing hydrogen. Here, we report a quadruple perovskite oxide CaCu3Ru4O12 as a superior catalyst for acidic water oxidation. This complex oxide exhibits an ultrasmall overpotential of 171 mV at 10 mA cm−2geo, which is much lower than that of the state-of-the-art RuO2. Moreover, compared to RuO2, CaCu3Ru4O12 shows a significant increase in mass activity by more than two orders of magnitude and much better stability. Density functional theory calculations reveal that the quadruple perovskite catalyst has a lower Ru 4d-band center relative to RuO2, which effectively optimizes the binding energy of oxygen intermediates and thereby enhances the catalytic activity.

Revealing the Reactivity of the Iridium Trioxide Intermediate for the Oxygen Evolution Reaction in Acidic Media

The development of efficient water splitting heterogeneous catalysts in acidic media is largely hampered by both the slow kinetics of the oxygen evolution reaction (OER) and the limited stability of the electrocatalyst under these harsh working conditions. At the origin of both the activity and the instability of iridium oxides used as OER catalysts in acid conditions is the formation of high-valence IrOx intermediates such as IrO3. Nevertheless, owing to its reactivity with water, this intermediate was never stabilized, and its electrochemical/chemical behavior was never studied in depth. Here, we report a strategy to stabilize this elusive IrO3 intermediate. Furthermore, we demonstrate that upon reactivity with water, gaseous oxygen is generated, while the intermediate is protonated following the reaction IrO3 + xH2O → H2xIrO3 + x/2O2. The resulting hydrated iridium oxide H2IrO3, which possesses three-dimensional proton intercalation/deintercalation channels, can be considered as an enlightening OER mod...

Cover Feature: Boosting Stability and Activity of Oxygen Evolution Catalyst in Acidic Medium: Bimetallic Ir−Fe Oxides on Reduced Graphene Oxide Prepared through Ultrasonic Spray Pyrolysis (ChemCatChem 11/2019)

Cover Feature: Boosting Stability and Activity of Oxygen Evolution Catalyst in Acidic Medium: Bimetallic Ir−Fe Oxides on Reduced Graphene Oxide Prepared through Ultrasonic Spray Pyrolysis (ChemCatChem 11/2019)

Glucose-derived carbon supported well-dispersed CrN as competitive oxygen reduction catalysts in acidic medium

In this work, a glucose-derived carbon supported CrN composite is prepared by using a hydrothermal method and followed by a nitridating process. It is found that CrN nanoparticles in the composite are well-dispersed and separated by the carbon support. More importantly, the composite exhibits significantly enhanced oxygen reduction reaction activity than free-standing aggregated CrN nanoparticles, especially in acidic medium. The onset potential of the composite reaches 0.81 V in acidic medium, which is one of the highest values among the reported metal nitrides. The rotating ring disk electrode results indicate that the composite is more beneficial to O2 dissociation than free-standing CrN nanoparticles. Results of X-ray photoelectron spectroscopy, O2 temperature-programmed desorption and electrochemical impedance spectroscopy indicate that the significantly enhanced oxygen reduction reaction activity of the composite over free-standing CrN is derived not from the new formed active sites or enhanced oxygen adsorption but from the much enhanced electron transfer rate. This observation helps to understand the role of electron transfer rate playing in the oxygen reduction reaction activity of metal nitrides.

(Invited) PGM-Free Oer Catalysts for PEM Electrolyzer Application

Low temperature water electrolysis represents one of the critical technologies in distributed hydrogen production. It produces clean hydrogen with fast response time and works well when coupled with renewable but intermittent power sources such as wind and solar. Low temperature electrolysis can be operated using either proton exchange or alkaline membrane electrolyte. Compared to alkaline electrolyzer, proton exchange membrane (PEM) electrolyzer offers advantages of significantly higher current density (x5 improvement) and higher H2 purity, rendering it a preferred technology when high energy efficiency and low footprint are essential. Working in the oxidative and acidic environment under high polarization voltage, however, adds substantial demand to the electrode catalyst and the support. This is particularly the case at anode where the oxygen evolution reaction (OER) takes place. At present, the PGM materials such as Ir black or Ir oxide are catalysts of choice. Their high cost and limited reserve, however, limit the broad implementation of PEM electrolyzer in the renewable energy landscape. Low-cost transition metal based catalysts are known to be active toward OER in alkaline electrolyte but not in acid. Furthermore, traditional catalyst support such as porous carbon cannot sustain the oxidative potential before being oxidized to CO2. Argonne National Laboratory has recently designed and synthesized a new class of PGM-free OER catalyst for PEM electrolyzer. The new catalysts are consisted of highly porous yet stable transition metal composite derived from the metal-organic-frameworks (MOFs). The new catalysts are also integrated into a porous nano-network electrode architecture to improve the conductivity, mass transport and durability against oxidative corrosion. Two catalyst series, ANL-Cat-A and ANL-Cat-B, were developed and investigated. The OER catalyst activity and durability were first measured by the catalytic layer coated over rotating disk electrode (RDE) method or carbon paper in half-cell containing strongly acidic media. Very promising OER activities were achieved. For example, the half-cell OER current density as the function of the polarization potential of a representative ANL-Cat-A (catalyst loading of 2 mg/cm2) was compared with that of Ir-black (catalyst loading of 0.2 mg/cm2). ANL-Cat-A achieved an OER potential of 1.584 V vs. RHE at the current density of 10 mA/cm2, which is only 29 mV higher than that of Ir black benchmark. The catalyst durability was measured through the multiple potential cycling from the voltage of 1.2 V to 2.0 V (vs. RHE) in the acidic electrolyte. The percentage of current density retention against the initial value was measured as the gauge for stability. Both ANL catalysts demonstrated excellent activity and durability over most of PGM-free catalysts in acidic medium. For example, one ANL-Cat-A catalyst retained 90% and 80% current densities at 1.8 V and 2.0 V after 2,000 voltage cycles, respectively. In contrast, the percentage of the current density retention for Ir black was dramatically decreased after only 1000 voltage cycles. Several catalysts from ANL-Cat-A and –B series were also integrated into membrane electrode assemblies and tested in PEM electrolyzer at Giner Inc. under operating condition (60 °C and ambient pressure). Important processing parameters, such as anode catalyst loading, ionomer-to-catalyst ratio, pretreatment and application methods, have been systematically studied. Several MEAs demonstrated OER current density > 200 mA/cm2 at 1.8 V. This work collaborates with DOE HydroGen Consortium in computational modeling, surface property characterization and advanced electron microscopic imaging. Acknowledgement: This work is supported by U. S. Department of Energy, Fuel Cell Technologies Office through Office of Energy Efficiency and Renewable Energy. The works performed at Argonne National Laboratory’s Center for Nanoscale Materials, an U.S. Department of Energy Office of Science User Facility, is supported by Office of Science, U.S. Department of Energy under Contract DE-AC02-06CH11357.

Boosting Stability and Activity of Oxygen Evolution Catalyst in Acidic Medium: Bimetallic Ir−Fe Oxides on Reduced Graphene Oxide Prepared through Ultrasonic Spray Pyrolysis

AbstractElectrolysis of water in acidic media generally requires noble metals (oxides) to enhance the catalyst activity and durability in the oxygen evolution reaction (OER). Bimetallic Ir−Fe supported on reduced graphene oxide (IFG) is prepared by ultrasonic spray pyrolysis, followed by acid and/or heat treatment. Physical and electrochemical methods are used to elucidate the effect of the physical and chemical properties of the IFG catalysts modified by spray pyrolysis and post treatment on the OER activity and stability under harshly oxidizing conditions in 0.1 M HClO4. The IFG‐AHT catalyst synthesized via ultrasonic pyrolysis followed by acid and heat treatment exhibits superior OER activity among the IFG catalysts. The mass activity was two‐fold higher and the stability is superior to that of the commercially available Ir catalyst, indicating that the metal (oxide) dissolution rate and the interaction between Ir and the hybrid support affect the cost and lifetime of OER catalysts.

Highly efficient and ORR active platinum-scandium alloy-partially exfoliated carbon nanotubes electrocatalyst for Proton Exchange Membrane Fuel Cell

Oxygen reduction reaction (ORR) in Proton Exchange Membrane Fuel Cell (PEMFC) is the most sluggish reaction, which impedes the performance and commercialization of PEMFC. Platinum-based alloys show higher ORR activity than Pt and it is suggested by density functional theory calculations that Pt3Sc alloy has high stability and higher ORR activity due to filling the metal d-bands and lowers binding energy of the oxygen species respectively. Herein, we report Pt3Sc alloy nanoparticles (NPs) dispersed over partially exfoliated carbon nanotubes (PECNTs) as a cathode catalyst for single-cell measurements of PEMFC where Pt3Sc alloy shows a lower binding energy towards oxygen and facilitates ORR with much faster kinetics. The ORR activity of Pt3Sc/PECNTs electrocatalyst, investigated by cyclic voltammetry, Rotating Disk electrode (RDE) and Rotating Ring Disk electrode (RRDE), shows the higher mass activity and lower H2O2 formation than the commercial catalyst Pt/C-TKK. Accelerated Durability Tests (ADT) was performed to evaluate the stability of catalysts in acidic medium. In single-cell measurements, Pt3Sc/PECNTs cathode catalyst exhibits a power density of 760 mW cm−2 at 60 °C. Our study gives an important insight into the design of a novel ORR electrocatalyst with an excellent stability and high power density of PEMFC.

A Dissolution/Precipitation Equilibrium on the Surface of Iridium-Based Perovskites Controls Their Activity as Oxygen Evolution Reaction Catalysts in Acidic Media.

Recently, IrV -based perovskite-like materials were proposed as oxygen evolution reaction (OER) catalysts in acidic media with promising performance. However, iridium dissolution and surface reconstruction were observed, questioning the real active sites on the surface of these catalysts. In this work, Sr2 MIr(V) O6 (M=Fe, Co) and Sr2 Fe0.5 Ir0.5 (V) O4 were explored as OER catalysts in acidic media. Their activities were observed to be roughly equal to those previously reported for La2 LiIrO6 or Ba2 PrIrO6 . Coupling electrochemical measurements with iridium dissolution studies under chemical or electrochemical conditions, we show that the deposition of an IrOx layer on the surface of these perovskites is responsible for their OER activity. Furthermore, we experimentally reconstruct the iridium Pourbaix diagram, which will help guide future research in controlling the dissolution/precipitation equilibrium of iridium species for the design of better Ir-based OER catalysts.

A Dissolution/Precipitation Equilibrium on the Surface of Iridium‐Based Perovskites Controls Their Activity as Oxygen Evolution Reaction Catalysts in Acidic Media

AbstractRecently, IrV‐based perovskite‐like materials were proposed as oxygen evolution reaction (OER) catalysts in acidic media with promising performance. However, iridium dissolution and surface reconstruction were observed, questioning the real active sites on the surface of these catalysts. In this work, Sr2MIr(V)O6(M=Fe, Co) and Sr2Fe0.5Ir0.5(V)O4were explored as OER catalysts in acidic media. Their activities were observed to be roughly equal to those previously reported for La2LiIrO6or Ba2PrIrO6. Coupling electrochemical measurements with iridium dissolution studies under chemical or electrochemical conditions, we show that the deposition of an IrOxlayer on the surface of these perovskites is responsible for their OER activity. Furthermore, we experimentally reconstruct the iridium Pourbaix diagram, which will help guide future research in controlling the dissolution/precipitation equilibrium of iridium species for the design of better Ir‐based OER catalysts.

Kinetic Understanding of the Reduction of Oxygen to Hydrogen Peroxide over an N-Doped Carbon Electrocatalyst

Nitrogen-doped carbon catalysts for the electrochemical oxygen reduction reaction (ORR) have great potential to substitute precious metal alloy catalysts for the electrochemical synthesis of H2O2 based on a fuel cell setup. Consequently, obtaining a kinetic understanding of nitrogen-doped carbon catalysts in acidic media is essential. In this study, the mathematically modified Damjanovic model and Nabae model were applied to calculate the kinetic constants for an N/C catalyst prepared from polyimide particles. The results show that the N/C catalyst has high selectivity for the two-electron reduction of O2, making it a promising catalyst for the electrochemical production of H2O2. This study gives quantitative insight into the oxygen reduction reaction mechanism over an N/C catalyst prepared by the pyrolysis of polyimide nanoparticles.

An 2D Polymer Used As Ingredient of Fe/N/C Composite Towards Oxygen Reduction Catalyst In Acidic Medium.

AbstractCarbon‐based transition metal/nitrogen material is one of the most promising non‐precious metal catalysts for the oxygen reduction reaction. And N‐containing polymers are considered as a kind of excellent N precursor because they are more likely to form ordered and stable carbon‐based active layer during heat treatment. However, further research is still needed due to the inferior oxygen reduction catalytic activity compared with Pt in acidic condition. Herein, we design the Fe/N/C catalyst through synthesize a special nitrogen‐rich polymer poly‐hexaazatrinaphthylene as N source and subsequently calcine with the mixture of ferric chloride and Vulcan XC‐72. The physical results indicate that the oxygen reduction catalytic activity is mainly related to the amorphous carbon, pyridinic‐N, and Fe‐N4 coordination geometry. Electrochemical tests indicated that the sample pyrolyzed at 800°C presents relative high oxygen reduction activity in 0.5 mol L−1 H2SO4 via an efficient four‐electron‐dominant pathway.

Low‐Work‐Function Silver Activating N‐doped Graphene as Efficient Oxygen Reduction Catalysts in Acidic Medium

AbstractNon‐platinum graphene‐based electrocatalysts are vital for low‐cost energy conversion by hydrogen fuel cell. However, high oxygen reduction reaction (ORR) overpotentials limit their efficiency and stability. Here, we propose a strategy to increase graphene Fermi level by graphene encapsulating a metal with lower work function than graphene, aiming to enhance the ORR activity of graphene‐based materials. As an example, Ag nanoparticles (function work, 4.2 eV) are embedded into N‐doped graphene (function work, 4.5 eV) (Ag@NG). The Ag@NG exhibits the ORR onset potential of 0.804 V and excellent stability over 10000 electrochemical cycles in acidic electrolyte. Spectroscopic analysis confirms Ag−N coordination bond as an efficient electron transfer route significantly benefiting upshift of graphene Fermi level that enhances the ORR activity and stability.

Small, Narrowly Distributed Iridium Nanoparticles Supported on Indium Tin Oxide for Efficient Anodic Water Oxidation

Decreasing the noble metal content while maintaining high catalytic activity is a critical requirement for the development of efficient anodic water oxidation catalysts in acidic media. In the pres...

Highly active and stable ruthenate pyrochlore for enhanced oxygen evolution reaction in acidic medium electrolysis

Developing active, acid-stable and cost-effective electrocatalysts for oxygen evolution reaction (OER) is a primary challenge to directly produce hydrogen from water electrolysis. IrO2 is the best-known catalyst in acid medium due to its good activity and stability, but it’s too expensive to be used in large amounts. To overcome this economical constraint, the use of low amount of iridium electrocatalyst is required. Recently, ruthenium pyrochlore oxides (A2Ru2O7−δ) as OER catalysts have drawn extensive interests due to reduced content of precious metal relative to RuO2 or IrO2, though their OER catalytic activity still needs to be further improved. In this work, we, for the first time, developed a highly active and stable Y1.85Zn0.15Ru2O7−δ electrocatalyst, the A site doped yttrium ruthenate pyrochlore for OER. The mechanism of A site doped ruthenate pyrochlore improving OER performance is revealed. The partial substitution of Y3+ ions by smaller Zn2+ leads to a formation of oxygen vacancies and mixed valences of Ru (Ru4+ and Ru5+), which, in turn, significantly alter the electronic properties and thus the electrocatalytic activity and electrical conductivity of the developed electrocatalyst for OER. The Y1.85Zn0.15Ru2O7−δ/acetylene black (AB) electrocatalyst exhibits sevenfold higher activity than the IrO2/AB reference catalyst; twofold higher activity than Y2Ru2O7−δ/AB, with a Tafel slope of 36.9 mV dec−1; and higher stability than IrO2/AB in acidic media. Using a home-made proton exchange membrane electrolyser device, a high cell performance is achieved at 25 °C with an electrolysis current density of 0.46 A cm-2, confirming a promising prospect of Y1.85Zn0.15Ru2O7−δ electrocatalyst for practical water electrolysis applications.

Enhanced oxygen reduction on graphene via Y5Si3 electride substrate: A first-principles study

Manipulating the chemical reactivity of graphene toward oxygen reduced reduction (ORR) is of particular interest for both fundamental research and practical application in fuel cell. Deposing graphene on selected substrate provides a structure-intact strategy to enhance its chemical reactivity due to substrate-induced charge and interface effect. Here, we report the graphene deposited on one-dimensional electride Y5Si3 as an effective ORR catalyst in acidic media. Thermodynamic calculations suggest that depositing graphene on electride materials can facilitate the protonation of O2, which is the rate-determining step based on the four-electron reaction pathway and thus promote the ORR activity. Further electronic calculations reveal that low work function (3.5 eV), superior electrical conductivity and slight charge transfer from substrate to graphene result in the enhanced ORR performance of graphene. These findings shed light on the rational design of ORR catalysts based on graphitic materials and emphasize the critical role of substrates for energy-related electro-chemical reactions.

Simple synthesis of nitrogen-doped porous carbon from Chinese steamed bread flour and its catalytic application for hydrogen evolution reaction

A cost-effective green synthesis method for nitrogen-doped porous carbon from Chinese steamed bread flour by successive hydrothermal treatment and pyrolysis is reported. The hydrothermal treatment remarkably enhances the strength of the resulting pyrolyzed carbon materials, enabling the facile fabrication of robust monolithic nitrogen-doped porous carbon with the yield of 44.33%. This nitrogen-doped porous carbon exhibits 3-dimensional porous structure which is mainly mesoporous and high surface area. The thin and 3-dimensional self-supported working electrode is made from the synthesized nitrogen-doped porous carbon without using any other current collector or polymeric binder. The hydrogen evolution reaction electrocatalytic activity in 0.5 M H2SO4 reveals the achievement of the low overpotential of ∼220 mV at 10 mA cm−2, a Tafel slope of ∼77 mV dec−1, a nearly 100% Faradaic yield, an excellent stability, and a low charge transfer resistance. The self-supported electrode exhibits higher electrocatalytic activity than the powder-state supported on graphite felt electrode. Its hydrogen evolution reaction electrocatalytic activity is better than that of the reported non-metal heteroatom-doped carbon catalysts and comparable to that of some metal catalysts in acidic media. The use of flour enables the cheap and facile fabrication of carbon electrode with tunable pore sizes and surface areas, making flour-based carbon electrodes highly promising.

Reaction Mechanism of a Novel IrOx-Based OER Catalyst in Acidic Media

The oxygen evolution reaction (OER) is of prime importance in multiple energy storage devices [1]. IrOx-based catalysts are thought to be the most promising candidates in acidic media, but have been limited by their high cost. Choosing suitable substrates for such catalysts are effective to reduce the Ir consumption as well as beneficial for the OER performance[2 - 4]. Here, we focus on the catalytic mechanism for a newly synthesized IrOx-based composite material which shows an excellent OER performance in acidic media. The catalytic mechanism has been revealed mainly based on in-situ measurements and DFT calculations. The detail mechanism will de presented at the meeting.