Unlocking Potential of Pyrochlore in Energy Systems via Soft Voting Ensemble Learning.

In traditional machine learning (ML)-based material design, the defects of low prediction accuracy, overfitting and low generalization ability are mainly caused by the training of a single ML model. Here, a Soft Voting Ensemble Learning (SVEL) approach is proposed to solve the above issues by integrating multiple ML models in the same scene, thus pursuing more stable and reliable prediction. As a case study, SVEL is applied to develop the broad chemical space of novel pyrochlore electrocatalysts with the molecular formula of A2B2O7, to explore promising pyrochlore oxides and accelerate predictions of unknown pyrochlore in the periodic table. The model successfully established the structure-property relationship of pyrochlore, and selected six cost-effective pyrochlore from the periodic table with a high prediction accuracy of 91.7%, all of which showed good electrocatalytic performance. SVEL not only effectively avoids the high costs of experimentation and lengthy computations, but also addresses biases arising from data scarcity in single models. Furthermore, it has significantly reduced the research cycle of pyrochlore by ≈ 22 years, offering broad prospects for accelerating the development of materials genomics. SVEL method is intended to integrate multiple AI models to provide broader model training clues for the AI material design community.

Na Substitution Steering RuO6 Unit in Ruthenium Pyrochlores for Enhanced Oxygen Evolution in Acid.

Although Ruthenium-based pyrochlore oxides can function as promising catalysts for acidic water oxidation, their limitations in terms of stability and activity still need to be addressed for further application in practical conditions. In this work, the possibility to enhance both oxygen evolution reaction activity and durability of Gd2Ru2O7- δ through partial replacement with Na+ in Gd3+ sites is first offered, leading to the electronic and geometric regulation of active center RuO6. Na+ triggers the emergence of Ru<4+ and the electron rearrangement of active-centered RuO6. Specifically, Ru ions with a negative d-band center after Na+ doping exhibit weaker adsorption energies of *O and result in the conversion of the rate-limiting step from *O/*OOH to *OH/O*, reducing energy barriers for boosting activities. Therefore, the NaxGd2- xRu2O7- δ requires a low overpotential of 260 mV at 10 mA cm-2 in 0.1 m HClO4 electrolyte. Moreover, the higher formation energy of Ru vacancy and less distorted RuO6 enable the as-prepared NaxGd2- xRu2O7- δ to operate steadily at 10 mA cm-2 for 300 h and multi-current chronopotentiometry with current densities from 20 to 100 mA cm-2 for 60 h in acidic proton exchange membrane electrolyzer, respectively.

Surface Oxygen Defect Engineering of A2B2O7 Pyrochlore Semiconductors Boosts the Electrocatalytic Reduction of CO2-to-HCOOH.

The electrocatalytic conversion of inert CO2 to value-added chemical fuels powered by renewable energy is one of the benchmark approaches to address excessive carbon emissions and achieve carbon-neutral energy restructuring. However, the adsorption/activation of supersymmetric CO2 is facing insurmountable challenges that constrain its industrial-scale applications. Here, this theory-guided study confronts these challenges by leveraging the synergies of bimetallic sites and defect engineering, where pyrochlore-type semiconductor A2B2O7 is employed as research platform and the conversion of CO2-to-HCOOH as the model reaction. Specifically, defect engineering intensified greatly the chemisorption-induced CO2 polarization via the bimetallic coordination, thermodynamically beneficial to the HCOOH production via the *HCO2 intermediate. The optimal V-BSO-430 electrocatalyst with abundant surface oxygen vacancies achieved a superior HCOOH yield of 116.7 mmol h-1 cm-2 at -1.2 VRHE, rivalling the incumbent similar reaction systems. Furthermore, the unique catalytic unit featured with a Bi1-Sn-Bi2 triangular structure, which is reconstructed by defect engineering, and altered the pathway of CO2 adsorption and activation to allow the preferential affinity of the suspended O atom in *HCO2 to H. As a result, V-BSO-430 gave an impressive FEHCOOH of 93% at -1.0 VRHE. This study held promises for inspiring the exploration of bimetallic materials from the massive semiconductor database.

Novel pyrochlore type europium stannate - tungsten disulfide heterostructure for light driven carbon dioxide reduction and nitrogen fixation.

The reduction of carbon dioxide (CO2) and nitrogen (N2) to value-added products is a substantial area of research in the fields of sustainable chemistry and renewable energy that aims at reducing greenhouse gas emissions and the production of alternative fuels and chemicals. The current work deals with the synthesis of pyrochlore-type europium stannate (Eu2Sn2O7: EuSnO), tungsten disulfide (WS2:WS), and novel EuSnO/WS heterostructure by a simple and facile co-precipitation-aided hydrothermal method. Using different methods, the morphological and structural analyses of the prepared samples were characterized. It was confirmed that a heterostructure was formed between the cubic EuSnO and the layered WS. Synthesized materials were used for photocatalytic CO2 and N2 reduction under UV and visible light. The amount of CO and CH4 evolved due to CO2 reduction is high in EuSnO/WS (CO = 104, CH4 = 64 µmol h-1 g-1) compared to pure EuSnO (CO = 36, CH4 = 70 µmol h-1 g-1) and WS (CO = 22, CH4 = 1.8 µmol h-1 g-1) under visible light. The same trend was observed even in the N2 fixation reaction under visible light, and the amount of NH4+ produced was found to be 13, 26, and 41 µmol h-1 g-1 in the presence of WS, EuSnO and EuSnO/WS, respectively. Enhanced light-driven activity towards CO2 and N2 reduction reactions in EuSnO/WS is due to the efficient charge separation through the formation of type-II heterostructure, which is in part associated with photocurrent response, photoluminescence, and electrochemical impedence spectroscopic (EIS) results. The EuSnO/WS heterostructure's exceptional stability and reusability may pique the attention of pyrochlore-based composite materials in photocatalytic energy and environmental applications.

High-performance AEM unitized regenerative fuel cell using Pt-pyrochlore as bifunctional oxygen electrocatalyst.

The performance of fixed-gas unitized regenerative fuel cells (FG-URFCs) are limited by the bifunctional activity of the oxygen electrocatalyst. It is essential to have a good bifunctional oxygen electrocatalyst which can exhibit high activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this regard, Pt-Pb2Ru2O7-x is synthesized by depositing Pt on Pb2Ru2O7-x wherein Pt individually exhibits high ORR while Pb2Ru2O7-x shows high OER and moderate ORR activity. Pt-Pb2Ru2O7-x exhibits higher OER (η@10mAcm-2 = 0.25 ± 0.01 V) and ORR (η@-3mAcm-2 = -0.31 ± 0.02 V) activity in comparison to benchmark OER (IrO2, η@10mAcm-2 = 0.35 ± 0.02 V) and ORR (Pt/C, η@-3mAcm-2 = -0.33 ± 0.02 V) electrocatalysts, respectively. Pt-Pb2Ru2O7-x shows a lower bifunctionality index (η@10mAcm-2, OER- η@-3mAcm-2, ORR) of 0.56 V with more symmetric OER-ORR activity profile than both Pt (>1.0 V) and Pb2Ru2O7-x (0.69 V) making it more useful for the AEM (anion exchange membrane) URFC or metal-air battery applications. FG-URFC tested with Pt-Pb2Ru2O7-x and Pt/C as bifunctional oxygen electrocatalyst and bifunctional hydrogen electrocatalyst, respectively, yields a mass-specific current density of 715 ± 11 A/gcat-1 at 1.8 V and 56 ± 2 A/gcat-1 at 0.9 V under electrolyzer mode and fuel-cell mode, respectively. The FG-URFC shows a round-trip efficiency of 75% at 0.1 A/cm-2, underlying improvement in AEM FG-URFC electrocatalyst design.

Dry Reforming of Methane over Pyrochlore-Type La2Ce2O7-Supported Ni Catalyst: Effect of Particle Size of Support.

The properties of supports (such as oxygen vacancies, oxygen species properties, etc.) significantly impact the anti-carbon ability due to their promotional effect on the activation of CO2 in dry reforming of methane (DRM). Herein, pyrochlore-type La2Ce2O7 compounds prepared using co-precipitation (CP), glycine nitrate combustion (GNC) and sol-gel (S-G) methods, which have highly thermal stability and unique oxygen mobility, are applied as supports to prepare Ni-based catalysts for DRM. The effect of the calcining temperature (500, 600 and 700 °C) on La2Ce2O7(CP) has also been investigated. Based on multi-technique characterizations, it is found that the synthesis method and calcination temperature can influence the particle size of the La2Ce2O7 support. Changes in particle size strongly modulate the pore volume, specific surface area and numbers of surface oxygen vacancies of the La2Ce2O7 support. As a result, the distribution of supported Ni components is affected due to the different metal-support interaction, thereby altering the activity of the catalysts for cracking CH4. Moreover, the supports' abilities to adsorb and activate CO2 are also adjusted accordingly, accelerating the removal of the carbon deposited on the catalysts. Finally, La2Ce2O7(CP 600) with an appropriate particle size exhibits the best catalytic activity and stability in DRM.

Nickel-based cerium zirconate inorganic complex structures for CO2 valorisation via dry reforming of methane.

The increasing anthropogenic emissions of greenhouse gases (GHG) is encouraging extensive research in CO2 utilisation. Dry reforming of methane (DRM) depicts a viable strategy to convert both CO2 and CH4 into syngas, a worthwhile chemical intermediate. Among the different active phases for DRM, the use of nickel as catalyst is economically favourable, but typically deactivates due to sintering and carbon deposition. The stabilisation of Ni at different loadings in cerium zirconate inorganic complex structures is investigated in this work as strategy to develop robust Ni-based DRM catalysts. XRD and TPR-H2 analyses confirmed the existence of different phases according to the Ni loading in these materials. Besides, superficial Ni is observed as well as the existence of a CeNiO3 perovskite structure. The catalytic activity was tested, proving that 10 wt.% Ni loading is the optimum which maximises conversion. This catalyst was also tested in long-term stability experiments at 600 and 800°C in order to study the potential deactivation issues at two different temperatures. At 600°C, carbon formation is the main cause of catalytic deactivation, whereas a robust stability is shown at 800°C, observing no sintering of the active phase evidencing the success of this strategy rendering a new family of economically appealing CO2 and biogas mixtures upgrading catalysts.

Insulator-transition-induced Degradation of Pyrochlore Ruthenates in Electrocatalytic Oxygen Evolution and Stabilization through Doping.

Ru-based pyrochlores (e.g., Y2Ru2O7-d) are promised to replace IrO2 in polymer electrolyte membrane (PEM) electrolyzers. It is significant to reveal the cliff attenuation on the oxygen evolution reaction (OER) performance of these pyrochlores. In this work, we monitor the structure changes and electrochemical behavior of Y2Ru2O7-d over the OER process, and it is found that the reason of decisive OER inactivation is derived from an insulator transition occurred within Y2Ru2O7-d due to its inner ²perfecting² lattice induced by continuous atom rearrangement. Therefore, a stabilization strategy of the Ir-substituted Y2Ru2O7-d is proposed to alleviate this undesirable behavior. The double-exchange interaction between Ru and Ir in [RuO6] and [IrO6] octahedra leads the charge redistribution with simultaneous spin configuration adjustment. The electronic state in newly formed octahedrons centered with Ru 4d3 (with the state of eg'2--a1g-1 eg0) and Ir 5d6 (eg'4a1g-2 eg0) relieves the uneven electron distributions in [RuO6] orbital. The attenuated Jahn-Teller effect alleviates atom rearrangement, represented as the mitigation of insulator transition, surface reconstruction, and metal dissolution. As results, the Ir-substituted Y2Ru2O7-d presents the greatly improved OER stability and PEM durability. This study unveils the OER degradation mechanism and stabilization strategy for material design of Ru-based OER catalysts for electrochemical applications.

Role of MoOx Surficial Modification in Enhancing the OER Performance of Ru-Pyrochlore.

Pyrochlore ruthenate (Y2 Ru2 O7-δ ) is highlighted as a promising oxygen evolution reaction (OER) catalyst for water splitting in polymer electrolyte membrane electrolyzers. However, an efficient electronic modulation strategy for Y2 Ru2 O7-δ is required to overcome its electrochemical inertness. Herein, a surface manipulation strategy involving implanting MoOx moieties on nano Y2 Ru2 O7-δ (Mo-YRO) using wet chemical peroxone method is demonstrated. In contrast to electronic structure regulation by intramolecular charge transfer (i.e., substitutional strategies), the heterogeneous Mo-O-Ru micro-interfaces facilitate efficient intermolecular electron transfer from [RuO6 ] to MoOx . This eliminates the bandgap by inducing Ru 4d delocalization and band alignment rearrangement. The MoOx modifiers also alleviate distortion of [RuO6 ] by shortening Ru-O bond and enlarging Ru-O-Ru bond angle. This electronic and geometric structure tailoring enhances the OER performance, showing a small overpotential of 240 mV at 10 mA cm-2 . Moreover, the electron-accepting MoOx moieties provide more electronegative surfaces, which serve as a protective "fence" to inhibit the dissolution of metal ions, thereby stabilizing the electrochemical activity. This study offers fresh insights into the design of new-based pyrochlore electrocatalysts, and also highlights the versatility of surface engineering as a way of optimizing electronic structure and catalytic performance of other related materials.

Unique κ-Ce2Zr2O8 Superstructure Promoting the NOx Adsorption-Selective Catalytic Reduction (AdSCR) Performance of the WO3/CeZrOx Catalyst.

Selective catalytic reduction of NOx by NH3 (NH3-SCR) for diesel emission control at low temperatures is still a great challenge due to the limit of the urea injection threshold and inferior SCR activity of state-of-the-art catalyst systems below 200 °C. Fabricating bifunctional catalysts with both low temperature NOx adsorption-storage capacity and medium-high temperature NOx reduction activity is an effective strategy to solve the issues mentioned above but is rarely investigated. Herein, the WO3/Ce0.68Zr0.32Ox (W/CZ) catalyst containing the κ-Ce2Zr2O8 pyrochlore structure was successfully developed by a simple H2 reduction method, not only showing superior NOx adsorption-storage ability below 180 °C but also exhibiting excellent NH3-SCR activity above 180 °C. The presence of the pyrochlore structure effectively increased the oxygen vacancies on the κ-Ce2Zr2O8-containing W/CZ catalyst with enhanced redox property, which significantly promoted the NOx adsorption-storage as active nitrate species below 180 °C. Upon NH3 introduction above 180 °C, the κ-Ce2Zr2O8-containing W/CZ catalyst showed greatly improved NOx reduction performance, suggesting that the pyrochlore structure played a vital role in improving the NOx adsorption-selective catalytic reduction (AdSCR) performance. This work provides a new perspective for designing bifunctional CeZrOx-based catalysts to efficiently control the NOx emissions from diesel engines during the cold-start process.

Multiphase magnetism in Yb2Ti2O7.

We use neutron scattering to show that ferromagnetism and antiferromagnetism coexist in the low T state of the pyrochlore quantum magnet [Formula: see text] While magnetic Bragg peaks evidence long-range static ferromagnetic order, inelastic scattering shows that short-range correlated antiferromagnetism is also present. Small-angle neutron scattering provides direct evidence for mesoscale magnetic structure that we associate with metastable antiferromagnetism. Classical Monte Carlo simulations based on exchange interactions inferred from [Formula: see text]-oriented high-field spin wave measurements confirm that antiferromagnetism is metastable within the otherwise ferromagnetic ground state. The apparent lack of coherent spin wave excitations and strong sensitivity to quenched disorder characterizing [Formula: see text] is a consequence of this multiphase magnetism.

Fuel and oxygen harvesting from Martian regolithic brine.

NASA's current mandate is to land humans on Mars by 2033. Here, we demonstrate an approach to produce ultrapure H2 and O2 from liquid-phase Martian regolithic brine at ∼-36 °C. Utilizing a Pb2Ru2O7-δ pyrochlore O2-evolution electrocatalyst and a Pt/C H2-evolution electrocatalyst, we demonstrate a brine electrolyzer with >25× the O2 production rate of the Mars Oxygen In Situ Resource Utilization Experiment (MOXIE) from NASA's Mars 2020 mission for the same input power under Martian terrestrial conditions. Given the Phoenix lander's observation of an active water cycle on Mars and the extensive presence of perchlorate salts that depress water's freezing point to ∼-60 °C, our approach provides a unique pathway to life-support and fuel production for future human missions to Mars.

Defect Pyrochlore-Type Mott-Schottky Photocatalysts for Enhanced Ammonia Synthesis at Low Pressure.

The ambient ammonia synthesis coupled with distributed green hydrogen production technology can provide promising solutions for low-carbon NH3 production and H2 storage. Herein, we reported Ru-loaded defective pyrochlore K2 Ta2 O6-x with remarkable visible-light absorption and a very low work function, enabling effective visible-light-driven ammonia synthesis from N2 and H2 at low pressure down to 0.2 atm. The photocatalytic rate was 2.8 times higher than that of the best previously reported photocatalyst and the photo-thermal rate at 425 K was similar to that of Ru-loaded black TiO2 at 633 K. Compared to perovskite-type KTaO3-x with the same composition, the pyrochlore exhibited a 3.7-fold increase in intrinsic activity due to a higher photoexcited charge separation efficiency and a higher conduction band position. The interfacial Schottky barrier and spontaneous electron transfer between K2 Ta2 O6-x and Ru further improve photoexcited charge separation and accumulate energetic electrons to facilitate N2 activation.

Iridium Doped Pyrochlore Ruthenates for Efficient and Durable Electrocatalytic Oxygen Evolution in Acidic Media.

Developing highly active, durable, and cost-effective electrocatalysts for the oxygen evolution reaction (OER) is of prime importance in proton exchange membrane (PEM) water electrolysis techniques. Ru-based catalysts have high activities but always suffer from severe fading and dissolution issues, which cannot satisfy the stability demand of PEM. Herein, a series of iridium-doped yttrium ruthenates pyrochlore catalysts is developed, which exhibit better activity and much higher durability than commercial RuO2 , IrO2 , and most of the reported Ru or Ir-based OER electrocatalysts. Typically, the representative Y2 Ru1.2 Ir0.8 O7 OER catalyst demands a low overpotential of 220 mV to achieve 10 mA cm-2 , which is much lower than that of RuO2 (300 mV) and IrO2 (350 mV). In addition, the catalyst does not show obvious performance decay or structural degradation over a 2000 h stability test. EXAFS and XPS co-prove the reduced valence state of ruthenium and iridium in pyrochlore contributes to the improved activity and stability. Density functional theory reveals that the potential-determining steps barrier of OOH* formation is greatly depressed through the synergy effect of Ir and Ru sites by balancing the d band center and oxygen intermediates binding ability.

Luminescence study of Sm3+ ,Eu3+ -doped Y2 Zr2 O7 host: optical investigation of greenish yellow to red colour tunable pyrochlore phosphor.

Pyrochlore phosphors have shown their worth in modern day lighting in the last few years. Colour tunability of the phosphor is one of the modern techniques used to obtain white light-emitting diodes (WLEDs). In the proposed work, Y2 Zr2 O7 :Sm3+ ,Eu3+ phosphors were investigated for WLED applications as well as display devices. A convectional solid-state diffusion method was used to synthesize the proposed phosphors. X-ray diffraction of the proposed phosphors was performed and compared with the standard Inorganic Crystal Structure Database. The crystal structure of the sample was cubic in nature, obtained from Rietveld refinement. Vibrational and morphological studies on the samples were carried out using Fourier transform infrared spectroscopy and scanning electron microscopy analysis. The photoluminescence study of the colour tunable phosphor showed the characteristic peak of Sm3+ together with the two sharp peaks of Eu3+ ions. Greenish yellow to red colour tunability was observed in the proposed phosphor with enhancement of Eu3+ ions. All these results showed the worth of this sample for WLEDs applications as well as in display devices.

A First-Principles Investigation on the Structural, Optoelectronic, and Thermoelectric Properties of Pyrochlore Oxides (La2Tm2O7 (Tm = Hf, Zr)) for Energy Applications.

A first-principles calculation based on DFT investigations on the structural, optoelectronic, and thermoelectric characteristics of the newly designed pyrochlore oxides La2Tm2O7 (Tm = Hf, Zr) is presented in this study. The main quest of the researchers working in the field of renewable energy is to manufacture suitable materials for commercial applications such as thermoelectric and optoelectronic devices. From the calculated structural properties, it is evident that La2Hf2O7 is more stable compared to La2Zr2O7. La2Hf2O7 and La2Zr2O7 are direct bandgap materials having energy bandgaps of 4.45 and 4.40 eV, respectively. No evidence regarding magnetic moment is obtained from the spectra of TDOS, as a similar overall profile for both spin channels can be noted. In the spectra of ε2(ω), it is evident that these materials absorb maximum photons in the UV region and are potential candidates for photovoltaic device applications. La2Tm2O7 (Tm = Hf, Zr) are also promising candidates for thermoelectric device applications, as these p-type materials possess ZT values of approximately 1, which is the primary criterion for efficient thermoelectric materials.

Trace element partitioning between pyrochlore, microlite, fersmite and silicate melts.

We present experimentally determined trace element partition coefficients (D) between pyrochlore-group minerals (Ca2(Nb,Ta)2O6(O,F)), Ca fersmite (CaNb2O6), and silicate melts. Our data indicate that pyrochlores and fersmite are able to strongly fractionate trace elements during the evolution of SiO2-undersaturated magmas. Pyrochlore efficiently fractionates Zr and Hf from Nb and Ta, with DZr and DHf below or equal to unity, and DNb and DTa significantly above unity. We find that DTa pyrochlore-group mineral/silicate melt is always higher than DNb, which agrees with the HFSE partitioning of all other Ti-rich minerals such as perovskite, rutile, ilmenite or Fe-Ti spinel. Our experimental partition coefficients also show that, under oxidizing conditions, DTh is higher than corresponding DU and this implies that pyrochlore-group minerals may fractionate U and Th in silicate magmas. The rare earth element (REE) partition coefficients are around unity, only the light REE are compatible in pyrochlore-group minerals, which explains the high rare earth element concentrations in naturally occurring magmatic pyrochlores.

Structural Evolution and Magnetic Properties of Gd2Hf2O7 Nanocrystals: Computational and Experimental Investigations.

Structural evolution in functional materials is a physicochemical phenomenon, which is important from a fundamental study point of view and for its applications in magnetism, catalysis, and nuclear waste immobilization. In this study, we used x-ray diffraction and Raman spectroscopy to examine the Gd2Hf2O7 (GHO) pyrochlore, and we showed that it underwent a thermally induced crystalline phase evolution. Superconducting quantum interference device measurements were carried out on both the weakly ordered pyrochlore and the fully ordered phases. These measurements suggest a weak magnetism for both pyrochlore phases. Spin density calculations showed that the Gd3+ ion has a major contribution to the fully ordered pyrochlore magnetic behavior and its cation antisite. The origin of the Gd magnetism is due to the concomitant shift of its spin-up 4f orbital states above the Fermi energy and its spin-down states below the Fermi energy. This picture is in contrast to the familiar Stoner model used in magnetism. The ordered pyrochlore GHO is antiferromagnetic, whereas its antisite is ferromagnetic. The localization of the Gd-4f orbitals is also indicative of weak magnetism. Chemical bonding was analyzed via overlap population calculations: These analyses indicate that Hf-Gd and Gd-O covalent interactions are destabilizing, and thus, the stabilities of these bonds are due to ionic interactions. Our combined experimental and computational analyses on the technologically important pyrochlore materials provide a basic understanding of their structure, bonding properties, and magnetic behaviors.

Unveiling the Catalytic Origin of Nanocrystalline Yttrium Ruthenate Pyrochlore as a Bifunctional Electrocatalyst for Zn-Air Batteries.

Zn-air batteries suffer from the slow kinetics of oxygen reduction reaction (ORR) and/or oxygen evolution reaction (OER). Thus, the bifunctional electrocatalysts are required for the practical application of rechargeable Zn-air batteries. In terms of the catalytic activity and structural stability, pyrochlore oxides (A2[B2-xAx]O7-y) have emerged as promising candidates. However, a limited use of A-site cations (e.g., lead or bismuth cations) of reported pyrochlore catalysts have hampered broad understanding of their catalytic effect and structure. More seriously, the catalytic origin of the pyrochlore structure was not clearly revealed yet. Here, we report the new nanocrystalline yttrium ruthenate (Y2[Ru2-xYx]O7-y) with pyrochlore structure. The prepared pyrochlore oxide demonstrates comparable catalytic activities in both ORR and OER, compared to that of previously reported metal oxide-based catalysts such as perovskite oxides. Notably, we first find that the catalytic activity of the Y2[Ru2-xYx]O7-y is associated with the oxidations and corresponding changes of geometric local structures of yttrium and ruthenium ions during electrocatalysis, which were investigated by in situ X-ray absorption spectroscopy (XAS) in real-time. Zn-air batteries using the prepared pyrochlore oxide achieve highly enhanced charge and discharge performance with a stable potential retention for 200 cycles.

A Porous Pyrochlore Y2 [Ru1.6 Y0.4 ]O7-δ Electrocatalyst for Enhanced Performance towards the Oxygen Evolution Reaction in Acidic Media.

A robust porous structure is often needed for practical applications in electrochemical devices, such as fuel cells, batteries, and electrolyzers. While templating approach is useful for the preparation of porous materials in general, it is not effective for the synthesis of oxide-based electrocatalysts owing to the chemical instability of disordered porous materials thus created. Now the synthesis of phase-pure porous yttrium ruthenate pyrochlore oxide using an unconventional porogen of perchloric acid is presented. The lattice oxygen defects are formed by the mixed-valence state of Ru4+/5+ through the partial substitution of Ru4+ with Y3+ cations, leading to the formation of mixed B-site Y2 [Ru1.6 Y0.4 ]O7-δ . This porous Y2 [Ru1.6 Y0.4 ]O7-δ electrocatalyst exhibits a turnover frequency (TOF) of 560 s-1 (at 1.5 V versus RHE) for the oxygen evolution reaction, which is two orders of magnitude higher than that of the RuO2 reference catalyst (5.41 s-1 ).