Pure IrO2 Research Articles

Novel Ru-Based PEM Electrolysis Catalyst – Development from the Nano- to the Industrial-Scale

For the de-fossilization of sectors like chemicals, steel, and transportation, green H2 generated via water electrolysis provides a path towards net-zero. The broad use of H2 across hard-to-abate sectors confirms the urgent need for green hydrogen at scale.Within water electrolysis, there are several competing technologies: the so-called solid oxide electrolysis cell (SOEC), alkaline water electrolysis (AEL) and polymer electrolyte membrane electrolysis (PEM EL). Here, the latter shows significant benefits, such as high current density operation (> 2 A/cm2) and thus a smaller footprint, highly dynamic operation mode, high gas purity, and generation of pressurized hydrogen. However, at present, PEM EL requires precious metal catalysts; in particular, the O2 evolution on the anode currently relies on iridium, a metal which is rather scarce and expensive [1].To meet the demand of iridium with respect to the announced increase in electrolyzer capacities in the multi-GW range, material innovation to reduce the use of this precious metal must be implemented. Successful catalyst and electrode developments have already been demonstrated in the BMBF funded project Kopernikus P2X, whereby loadings of approx. 0.3 mg/cm2 (< 0.1 g/kW1) have been achieved without any significant losses in activity over time [2, 3].Here, we present a material innovation in the form of Ru-based electrocatalysts with a significantly reduced Ir content. This ruthenium-iridium oxide can be adjusted in a wide range of Ir content down to less than 15 wt.% (Ir). Consequently, iridium-based electrode loadings of less than 0.1 mg/cm2 and mass activities of about 3,500 A/g are feasible. Moreover, in accelerated degradation tests those mixed-oxides have demonstrated the often-missing stability by showing low degradation rates, similar to that of pure IrO2, in up to 30,000 potential-induced stress cycles.This achievement stems from a remarkable screening approach that combines synthesis, characterization and testing at the nanoscale at Mattiq, and on industrial scale in the multi-gram range at Heraeus Precious Metals GmbH & Co. KG. Remarkably the alignment of degradation testing on both scales showcases the power of the applied method, providing a blueprint for high throughput screening for future material developments, both within water electrolysis and beyond.

Effect of B-Doping and Manifestation on TiO2-Supported IrO2 for Oxygen Evolution Reaction in Water Electrolysis.

To commercialize hydrogen production by proton exchange membrane (PEM) electrolysis, the amount of rare and precious metal (iridium) required for anodic oxygen evolution reaction (OER) must be greatly reduced. In order to solve the problem, carrier loading is used to reduce the amount of iridium. Unlike the carrier modified by conventional metal element doping, this work doped the carrier with the nonmetallic element and then prepared IrO2/TiBxO2 composite catalyst using the Adams melting method. B-doped TiO2 supports with different doping amounts show the main phase rutile structure. Among them, the conductivity of B-doped carrier shows an increasing trend with the increase of doping amount, because boron can form holes and negative centers after doping, and more carriers improve the conductivity of the support. In addition, since element B is manifested from inside to outside on the support, B can affect the catalytic process. After the manifestation of element B, the carrier loaded with IrO2 exhibited superior electrocatalytic properties. The voltammetric charge per unit mass of 40IrO2/TiB0.3O2#2 (where #2 represents B after manifestation) reaches 1970 mC (cm2 mg)-1, the corresponding overpotential is 273 mV at a current density of 10 mA/cm-2, and the Tafel slope is 61.9 mV/dec Also, the charge transfer resistance is only 15 Ω. Finally, in the stability test, the composite catalyst is also better than pure IrO2 in the 20 000 s operation. Therefore, element B has an unexpectedly positive effect on the catalytic progress on the surface of the support after its manifestation.

Ir-IrO2 with heterogeneous interfaces and oxygen vacancies-rich surfaces for highly efficient oxygen evolution reaction

The development of efficient and stable catalysts for oxygen evolution reaction (OER) has recently attracted much attention, and the major challenge of current research is to offer fast kinetics and enhance the durability in a harsh oxidising environment. Herein, an effective strategy is developed to construct a unique heterogeneous interface between Ir nanoclusters and IrO2 via a facile and scalable chemical reduction method, followed by the thermal treatment under Ar atmosphere. Both the transmission electron microscope and X-ray photoelectron spectroscopy results revealed that the as-prepared Ir-IrO2 has been engineered with heterogeneous interfaces and oxygen vacancies-rich surfaces. Benefited from newly-formed active surfaces and the oxygen vacancies-rich surfaces, the Ir-IrO2 catalyst exhibits increased catalytic active sites and enhanced catalytic activity towards the OER compared with the pure IrO2 and commercial IrO2. The over-potential of the Ir-IrO2 is ca. 329 mV at 10 mA cm−2, and the mass activity is ca. 1851 A gIrO2−1 at 1.60 V (vs. RHE), about 2.4 times that of the commercial IrO2 (ca. 779 A gIrO2−1). In addition, both the improved catalytic performance and durability for the OER is further confirmed in PEM water electrolysis cell.

Development of IrO2–WO3 Composite Catalysts from Waste WC–Co Wire Drawing Die for PEM Water Electrolyzers’ Oxygen Evolution Reactions

Recycling waste materials as catalysts in the oxygen evolution reaction (OER) offers an innovative approach to reducing catalyst costs. Scrap tungsten carbide–cobalt (WC–Co) die, used in wire drawing processes in industrial applications, may be recovered as tungsten trioxide (WO3) by the electrolysis method. In this study, all composite catalysts were prepared as their weight percentage IW-x (0 ≤ x ≤ 100). Here, I, W, and x represent IrO2, WO3, and the weight percent of Ir in the mixed composite oxide, respectively. Then, the prepared IW-75, IW-50, and IrO2 catalysts are referred to as 75% IrO2–25% WO3, 50% IrO2–50% WO3, and Ir’s pure oxide form, respectively. These materials are compared with WO3 and IrO2 to investigate their OER performance. According to the linear sweep voltammetry results, the IW-75 catalyst has a 15.03% higher current density than the pure IrO2 catalyst. In the Tafel polarization curve of the catalysts, it is determined that the corrosion potential of IW-75 is enhanced, and the overpotential value is decreased 1.2 times compared to the synthesized IrO2 catalyst sample. As a result, using composite oxide from scrap wire drawing die and IrO2, the cost of the proton-exchange membrane water electrolyzer’s anode catalyst is reduced by more than 25%.

Supported RuxIr1‐xO2 Mixed Oxides Catalysts for Propane Combustion: Resistance Against Water Poisoning

AbstractMixed oxide catalysts RuxIr1‐xO2 with varying composition x (x=0, 0.25, 0.5, 0.75, 1.0) supported on CeO2, γ‐Al2O3 or ZrO2 are successfully prepared and tested in the catalytic propane combustion in terms of activity and stability. Pure IrO2 reveals a significantly lower activity than RuxIr1‐xO2 with x≥0.25. For low conversion, pure RuO2 on CeO2 turns out to be the most active catalyst, while at higher conversion, Ru0.75Ir0.25O2 on ZrO2 is found to be more active than RuO2, pointing towards synergism of Ru and Ir sites. Long‐term stability and also the resistance against water poisoning are highest for ZrO2‐supported catalysts. The higher the Ir concentration in the active component RuxIr1‐xO2 the more susceptible is the catalyst to water poisoning. Water poisoning is shown to be reversible, consistent with a blocking of catalytically active sites by water adsorption.

Comparable catalytic activity of a low-cost catalyst IrO2/TiO2 for methane conversion – A density functional theory study

Designing an efficient, low-cost catalyst is an important objective in the catalytic conversion of methane into value-added products that would be useful in many technological applications. Although IrO2 can activate C–H bonds at mild temperature and have excellent catalytic activity towards C–C coupling reactions, the high cost hinders its deployment. Herein, we propose IrO2 supported on TiO2 surface (IrO2/TiO2) and investigate its catalytic activity towards the methane dehydrogenation and the possibility of C–C coupling reactions with the help of density functional theory (DFT) calculations. Its catalytic performance is compared with that of a pure IrO2 surface. We find that the IrO2/TiO2 surface possesses similar adsorption characteristics of CH4 to the pure IrO2 surface. Our kinetic results indicate that the proposed catalyst exhibits similar enhanced catalytic activity towards methane activation and its successive dehydrogenation and C-C coupling reactions to that of pure IrO2 surface. We believe that methane can be more likely activated over the catalyst of one layer IrO2 supported on TiO2 at low temperatures, and it shows similar performances in thermodynamics like high-cost pure IrO2.

Phosphorus-induced reconstruction of Sub‐2 nm ultrafine spinel type CoO nanosheets for efficient water oxidation

The surface configuration of low‐cost spinel oxides for oxygen evolution reaction (OER) can significantly affect the electrochemical behavior by generating a thin oxyhydroxide layer and other structures on the surface. Herein, we design and construct phosphorus (P)-activated ~1.0 nm ultrathin CoO nanosheets (devoted as Px-CoO NSs) with enriched P-O bonds and high valence state Co active sites, which is beneficial to the OER process due to the balance with Co3+ and oxygen vacancies on the reconstructed surface/interface. In addition, such an ultrathin nanosheet structure is also benefit to expose more active sites and improve the intrinsic electronic conductivity. As a result, the surface reconstructed Px-CoO NSs show superior OER activity compared with pure CoO and IrO2 as benchmark. Furthermore, P1-CoO NSs demonstrate intrinsically high mass activity of 6.8 A gCo−1 at an overpotential of 270 mV, large turnover frequency of 0.0024 s−1 at an overpotential of 300 mV, and strong cycling stability in 0.1 M KOH solutions. Structural analysis further reveals that, as compared with CoO, the P-substitution not only induces the surface reconstruction into active Co oxyhydroxides under OER conditions, but also enhances the reaction kinetics. Undoubtedly, this work enriches the ways to prepare high-performance transition-metal-oxide-based catalyst for practical applications.

Constructing Supports–Network with N–TiO2 Nanofibres for Highly Efficient Hydrogen–Production of PEM Electrolyzer

Hydrogen production with a proton exchange membrane (PEM)electrolyzer utilized with renewable energy power is considered to be an efficient and clean green technique, but the poor oxygen evolution performance results in high energy consumption and low efficiency. In this work, a strategy is reported for the construction of a support network of the anodic catalyst layer to simultaneously ameliorate its sluggish reaction kinetics and mass transport in order to realize highly efficient hydrogen production of the PEM electrolyzer. After in situ synthesis of IrO2 nanoparticles on N–doped TiO2 nanofibers, the as–prepared IrO2/N–TiO2 electrode shows substantially enhanced Ir utilization and accelerated mass transport, consequently decreasing the corresponding cell potential of 107 mV relative to pure IrO2 at 2 A cm−2. The enhanced activity of IrO2/N–TiO2 could be due to the fact that the N–TiO2 nanofiber support can form a porous network, endowing IrO2/N–TiO2 with a large reactive contact interface and favorable mass transfer characters. The strategy in this work supplies a pathway to develop high–efficiency interfacial reaction materials for diverse applications.

Mixed RuxIr1–xO2 Oxide Catalyst with Well-Defined and Varying Composition Applied to CO Oxidation

The Pechini method allows for compositional and structural control of mixed ruthenium–iridium powder samples. Extensive characterization reveals that the calcination step leads to agglomerates with a metallic core that is encapsulated by the mixed RuxIr1–xO2 oxides. In the composition range of 21 up to 74 mol % ruthenium, the metal core reveals a miscibility gap with an Ir-rich fcc structure and a Ru-enriched hcp structure. Quite in contrast, the mixed oxide particles form a well-defined RuxIr1–xO2 solid solution throughout the entire composition range. Catalytic activity tests of the mixed RuxIr1–xO2 oxide catalysts are conducted with the prototypical CO oxidation reaction under oxidizing and under both stoichiometric reaction conditions; note that the metallic core is buried and does therefore not contribute to the activity. The least active catalyst is pure IrO2. At moderate reaction temperatures above 100 °C, the most active oxidation catalyst is identified with the Ir0.125Ru0.875O2 mixed oxide. All mixed RuxIr1–xO2 oxide catalysts are bulk-stable under the reaction conditions considered. However, upon CO oxidation reaction, the Ir4+ concentration at the mixed oxide surface is significantly enhanced with respect to its bulk composition. This information may be important for other catalytic oxidation reactions as well, such as the anodic oxygen evolution reaction in the electrocatalytic water splitting.

Iridium nanostructured metal oxide, its inclusion in silica matrix and their activity toward photodegradation of methylene blue

Precious metal oxides of IrO2 were prepared by thermal treatment of the macromolecular Chitosan●(IrCl3)X and PSP-4-PVP●(IrCl3)X precursors. Using this procedure, pure IrO2, phases were formed. The nature of the polymeric precursor is acting as a solid state template and influences the size of the iridium dioxide but not significantly the morphology, and the obtained IrO2 nanoparticles are about 15 nm. For the first time, the photocatalytic degradation of methylene blue using IrO2 was measured founding a moderated activity. The inclusion of IrO2 into SiO2 was performed using a combined solution of the Chitosan and PVP precursors by the sol-gel method. Subsequent pyrolysis of the isolated solid-state Chitosan●(IrCl3)x(SiO2)y and PSP-4-PVP●(IrCl3)x(SiO2)y give rise to the IrO2//SiO2 nanocomposites. The IrO2 particles are distributed uniformly inside the matrix of SiO2 leading to stable semi porous materials appropriate for high temperature catalytic applications. The IrO2 nanoparticles formed from the PVP precursor are mainly nanobars of 10 nm width, while that for the chitosan precursor are around 25 nm. The IrO2/SiO2 composites exhibit a moderate photocatalytic activity toward the degradation of methylene blue and similar to that of IrO2.

Synergistic cerium doping and MXene coupling in layered double hydroxides as efficient electrocatalysts for oxygen evolution

Oxygen evolution reaction (OER) is a bottle-neck process in many sustainable energy conversion systems due to its sluggish kinetics. The development of cost-effective yet efficient electrocatalysts towards OER is highly desirable but still a great challenge at current stage. Herein, a new type of hybrid nanostructure, consisting of two-dimensional (2D) Cerium-doped NiFe-layered double hydroxide nanoflakes directly grown on the 2D Ti3C2Tx MXene surface (denoted as NiFeCe-LDH/MXene), is designed using a facile in-situ coprecipitation method. The resultant NiFeCe-LDH/MXene hybrid presents a hierarchical nanoporous structure, high electrical conductivity and strong interfacial junction because of the synergistic effect of Ce doping and MXene coupling. As a result, the hybrid catalyst exhibits an excellent catalytic activity for OER, delivering a low onset overpotential of 197 mV and an overpotential of 260 mV at a current density of 10 mA·cm−2 in the alkaline medium, much lower than its pure LDH counterparts and IrO2 catalyst. Besides, the hybrid catalyst also displays a fast reaction kinetics and a remarkable stable durability. Further theoretic studies using density function theory (DFT) methods reveal that Ce doping could effectively narrow the bandgap of NiFe-LDH and reduce the overpotential in OER process. This work may shed light on the exploration of advanced electrocatalysts for renewable energy conversion and storage systems.

Mechanochemical processing of IrO2–Ta2O5: An alternative route for synthesizing Ir and Ir(Ta)O2 solid solution

This paper describes a study exploring milling and subsequent heat treatments of pure IrO2 and Ta2O5 powders. Reactants were milled under Ar atmosphere in a SPEX 8000D mill, with structural, morphological, and compositional characterizations (during milling and after subsequent heat treatments) by X-ray diffraction, energy-dispersive spectroscopy, and transmission electron microscopy. Electrochemical stability of powders was evaluated by open circuit potential (OCP). Results showed that the mechanical energy transferred during this process induces a reaction between IrO2 and Ta2O5, forming metallic Ir and Ir(Ta)O2 saturated solid solution. The study additionally shows that this reaction can be thermally induced with previous mechanical activation of reactants. Electrochemical evaluations of milled powders immersed in H2SO4 solution revealed that OCP shifts negatively with increasing milling time, approaching that of pure Ir at 15h milling.

IrO2 coated TiO2 core-shell microparticles advance performance of low loading proton exchange membrane water electrolyzers

Herein we present novel IrO2 coated TiO2 core-shell microparticles (IrO2@TiO2) as an oxygen evolution reaction catalyst. We compare the IrO2@TiO2 catalyst to commercial TiO2 supported IrO2 catalyst (IrO2/TiO2) and pure IrO2 catalyst powder. A stability analysis via on-line inductively coupled plasma mass spectrometry based on the S-number, a descriptor considering both energy efficiency and catalyst utilization efficiency, shows that the IrO2@TiO2 catalyst shows high potential for practical applications. This was further confirmed by full-cell tests showing superior performance of the IrO2@TiO2 catalyst with moderate and low loadings of 1.2 mgIr cm−2 and 0.4 mgIr cm−2, respectively. The core-shell catalyst is synthesized via facile route suitable for large quantities. Moreover, stable inks from the synthesized catalyst powder make this system appealing for large scale manufacturing of cells. Given the facile synthesis route, high activity, and good stability, the IrO2@TiO2 catalyst is potentially suitable for industry proton exchange membrane water electrolysis application.

Electrochemical behavior and corrosion resistance of IrO2-ZrO2 binary oxide coatings for promoting oxygen evolution in sulfuric acid solution

In this study, we prepared Ti/IrO2-ZrO2 electrodes with different ZrO2 contents using zirconium-n-butoxide (C16H36O4Zr) and chloroiridic acid (H2IrCl6) via a sol-gel route. To explore the effect of ZrO2 content on the surface properties and electrochemical behavior of electrodes, we performed physical characterizations and electrochemical measurements. The obtained results revealed that the binary oxide coating was composed of rutile IrO2, amorphous ZrO2, and an IrO2-ZrO2 solid solution. The IrO2-ZrO2 binary oxide coatings exhibited cracked structures with flat regions. A slight incorporation of ZrO2 promoted the crystallization of the active component IrO2. However, the crystallization of IrO2 was hindered when the added ZrO2 content was greater than 30at%. The appropriate incorporation of ZrO2 enhanced the electrocatalytic performance of the pure IrO2 coating. The Ti/70at%IrO2-30at%ZrO2 electrode, with its large active surface area, improved electrocatalytic activity, long service lifetime, and especially, lower cost, is the most effective for promoting oxygen evolution in sulfuric acid solution.

Mesoporous iridium oxide/Sb-doped SnO2 nanostructured electrodes for polymer electrolyte membrane water electrolysis

In proton exchange membrane (PEM) water electrolysis, iridium oxide (IrO2) has often been utilized as a main catalyst for the oxygen evolution reaction (OER) as a rate-determining step. In general, the performance of PEM water electrolysis is dominantly affected by the specific surface area and the porous structure of the IrO2 catalyst. Thus, in this study, IrO2 and antimony-doped tin oxide (ATO) nanostructures with high specific surface areas were synthesized through the Adams fusion method. The as-prepared samples showed well-defined porous high-crystalline nanostructures. The ATO nanoparticles as a support were surrounded by IrO2 nanoparticles as a catalyst without serious agglomeration, indicating that the IrO2 catalyst was uniformly distributed on the ATO support. Compared to pure IrO2, the IrO2/ATO mixture electrodes showed superior OER properties because of their increased electrochemical active sites.

Preparation of Sb-Doped SnO2 Nanoparticle with High Surface Area for Use As a Stable Anode Catalyst Support for PEM Electrolyzers.

Proton exchange membrane (PEM) water electrolysis has been considered as one of the most promising technologies for large H2 production. While the cost and stability of PEM are the main obstacles for the commercial application. Here we report a cost-effective catalyst, which consists of IrO2 nanoparticles supported on Sb-doped SnO2 (ATO). ATO support is synthesized by using templating process and hydrothermal method to improve its thermal stability. It has a mesoporous structure, small particle size, and high surface area. After loading IrO2 via Adams fusion method, the IrO2/ATO catalyst shows high electrochemical stability, according to repetitive potential cycling. This catalyst also shows a good electrochemical performance in single cell. Firstly, we prepared a series of ATO samples and named them as the Brunauer Emmett Teller model (BET) surface area. The surface area and pore size distribution of the obtained ATO samples were calculated by BET and nonlocal density functional theory (NLDFT). As shown in Fig.1a, the pore size become smaller with the increases of BET surface area, and the high surface area may be contributed to high synthesize temperature and long synthesize time. Secondly, we use the as-prepared ATO samples as catalysts support for IrO2, the catalysts named as BET surface area-IrO2 (e.g. 107-IrO2) and the IrO2 loading is 40 wt%. Fig.1b shows the cyclic voltammetry (CV) performance of different catalysts, it is quite clear that when supported by ATO, the voltammograms of these supported catalysts are dissimilar in shape from that of unsupported IrO2. The electrochemically active surface area (ECSA) of 170-IrO2 is obvious higher than the other ATO supported catalyst and a little higher than pure IrO2. This indicate that the 170 sample has the appropriate surface area as well as pore size distribution and it is best used as for IrO2 catalyst support. Finally, the accelerated degradation testing (ADT) was performed to investigated the durability of the 170-IrO2 catalyst in rotating disk electrode (RDE) test. As shown in Fig.1c the CV curves almost overlap before and after 9000 cycles’ ADT. Fig.1d shows the Linear sweep voltammetry (LSV) results of the catalyst samples before and after ADT. It is quite obvious that the 170-IrO2 catalyst is maintained stable with only a little loss in the catalytic activity. We have successfully made a series of ATO through templating process followed by hydrothermal method with different BET surface area and used as catalyst support for IrO2. The 170-IrO2 catalyst demonstrates high electrochemical performance and good stability. Herein, the as-synthesized ATO is considered to be a promising oxygen evolution catalyst support for solid polymer electrolyte water electrolyzer applications. Figure 1

Improving the Stability of DSA Electrodes by the Addition of TiO2 Nanoparticles

Dimensionally stable anodes (DSA) are widely used in water electrolysis, cathodic protection, wastewater treatment, metal electrowinning and chlor-alkali industry. An important parameter of these anodes is their lifetime under harsh anodic conditions. In this work, the incorporation of TiO2 nanoparticles into a thermally prepared IrO2 anode as a way of improving its service lifetime was investigated. The results show that incorporation of up to 25 wt% TiO2 nanoparticles into the coating formed crack-free structure during the thermal decomposition process and thus enhances the service lifetime of modified electrode dramatically by up to 10x compared to the pure IrO2 anode. Importantly, these nanoparticle additions have minimal effect of the anodes performance toward the oxygen evolution reaction. Further addition of TiO2 nanoparticles reduced the lifetime of the anode due to uneven distribution of the active coating over the substrate leading to electrolyte penetration to, and passivation of, the underlying titanium substrate. It is proposed that adding the right quantity of nanoparticles into the IrO2 layer improved the anodes lifetime by minimising electrolyte penetration to the substrate while increasing the mechanical strength of the layer.

Carbon-templated conductive oxide supports for oxygen evolution catalysis.

We present a novel route for the preparation of supported IrO2 catalysts for the oxygen evolution reaction in proton exchange membrane electrolyzers. It uses carbon soot as a nanostructure template, which is sequentially coated with a conductive niobium-doped titanium oxide (NTO) layer and an ultrathin, highly pure IrO2 catalyst layer by atomic layer deposition (ALD). The NTO acts as an oxidation-stable conductor between the metal current distributor and the catalyst. The highly controlled film growth by ALD enables the fabrication of electrodes with a very low noble metal loading. Nonetheless, these electrodes exhibit very high catalytic activity and good stability under cyclic and constant load conditions. At an IrO2 content of less than 10 percent by mass of the oxide material and an area-based Ir content of 153 μg cm-2, the nanostructured NTO/IrO2 electrode achieves an oxygen evolution current density of 1 mA cm-2 at an overpotential of ∼250 mV, which is significantly lower than the reported values for particulate NTO/IrO2 catalysts.

Iridium substitution in nickel cobaltite renders high mass specific OER activity and durability in acidic media

Oxygen evolution reactions being kinetically sluggish and highly expensive remains bottleneck in high pressure hydrogen production from acidic solution water electrolysis. Process economization is mostly affected due to larger consumption of precious iridium as an anodic catalyst. Therefore, effective utilization of noble metal remains a major challenge to be overwhelmed. Comprehensive theoretical and experimental studies show electronic dependency on different structural motifs of IrOx. However, due to lack of suitable non-noble host structures for iridium substitution there is hindrance in implementation. In current study, we explored inverse spinel, nickel cobaltite, as a host structure that provides OER beneficial structural motif to iridium sites on account of relatively higher IrO6 edge sharing than in rutile IrO2. Compact presence of octahedras in host structure reduces IrIr bond length for neighboring IrO6 octahedral units in it that further intrinsically improves the iridium sites due to electronic modulations. Specifically, composite comprising 20 mol% iridium in NiCo2-xO4 rendered acid stable 15 folds enhancement in mass specific OER activity relative to IrO2 resulting in substantial reduction of iridium content. Fabricated composite displayed an onset potential and tafel slope of 1.425 V and 40.4 mV dec−1, respectively in relative to 1.475 V and 68.1 mV dec−1 for pure IrO2. Current approach for effectively utilizing precious metal will lead in future for economizing hydrogen production via water splitting.

Boosted Performance of Ir Species by Employing TiN as the Support toward Oxygen Evolution Reaction.

Reducing the noble-metal loading without sacrificing the catalytic performance of the oxygen evolution reaction (OER) catalysts is paramount yet highly challenging. Herein, IrO2@Ir/TiN electrocatalysts employing TiN as the support have been developed and shown high efficiency toward OER. TiN is found not only to disperse the IrO2@Ir nanoparticles effectively but also to exert the electronic modulation of Ir by downshifting its d-band center of 0.21 eV compared to pure IrO2. Excitingly, TiN remarkably enhances the catalytic performance of Ir, where the overpotential to achieve the current density of 10 mA cm-2 is only 265 mV for the IrO2@Ir/TiN (60 wt %) catalyst. As a result, 71.7 wt % of the Ir metal can be saved to compare with the commercial Ir-black counterpart. Moreover, TiN can inhibit the aggregation and oxidative dissolution of Ir species, thereby enhancing the operational stability. The combined advantages of TiN open a new solution to reduce the anodic catalyst cost through boosting the catalytic activity and stability.