Participation Of Lattice Oxygen Research Articles

Understanding the Role of Strain on Electrochemical Reaction Kinetics: Oxygen Evolution on Mechanically Strained Rutile TiO2 As a Model System

Electrocatalysis offers a green alternative (when coupled with renewably-sourced electrons) to conventional carbon-intensive chemical fuel and commodity production processes. Electrochemical device efficiency, however, is limited by the sluggish kinetics of multi-electron transfer reactions, such as the oxygen evolution reaction (OER). Theoretical adsorption free energy scaling relationships predict large oxygen evolution overpotentials (>370 mV) for metal oxides performing the adsorbate evolution mechanism, a series of four proton-concerted electron transfer steps.1 Identifying catalyst design strategies that overcome or “break” scaling relations (i.e. strain,2 high entropy alloys,3 non-concerted proton and electron transfer mechanisms4,5) would provide a means to lower kinetic potential energy penalties and enhance the efficiency and economic incentives for further development of renewably-driven electrochemical reactions.Here we investigate the role of mechanically induced strain on the OER activity of polycrystalline rutile TiO2 thin films, grown on the super elastic alloy nitinol (NiTi) and mechanically strained by tensile tester. Our work characterizes how strain manifests in these complex polycrystalline systems with complementary physical characterization techniques (e.g. X-ray diffraction and Raman spectroscopy) and relates strain to OER performance in alkaline electrolytes. We contextualize our results within the framework of conventional adsorption scaling relationships to hypothesize how tensile strain influences reaction intermediate adsorption affinities, inferring implications for the OER kinetics of benchmark IrO2 and RuO2 catalysts that share the same crystal structure as the rutile TiO2 considered here.(1) Jaramillo, T. F.; Nørskov, J. K.; Rossmeisl, J. Universality in Oxygen Evolution Electrocatalysis on Oxide Surfaces. ChemCatChem 2011, 3 (7), 1159–1165. https://doi.org/10.1002/cctc.201000397.(2) Khorshidi, A.; Violet, J.; Hashemi, J.; Peterson, A. A. How Strain Can Break the Scaling Relations of Catalysis. Nat Catal 2018, 1 (4), 263–268. https://doi.org/10.1038/s41929-018-0054-0.(3) Kante, M. V.; Weber, M. L.; Ni, S.; van den Bosch, I. C. G.; van der Minne, E.; Heymann, L.; Falling, L. J.; Gauquelin, N.; Tsvetanova, M.; Cunha, D. M.; Koster, G.; Gunkel, F.; Nemšák, S.; Hahn, H.; Velasco Estrada, L.; Baeumer, C. A High-Entropy Oxide as High-Activity Electrocatalyst for Water Oxidation. ACS Nano 2023, 17 (6), 5329–5339. https://doi.org/10.1021/acsnano.2c08096.(4) Grimaud, A.; Diaz-Morales, O.; Han, B.; Hong, W. T.; Lee, Y.-L.; Giordano, L.; Stoerzinger, K. A.; Koper, M. T. M.; Shao-Horn, Y. Activating Lattice Oxygen Redox Reactions in Metal Oxides to Catalyse Oxygen Evolution. Nature Chem 2017, 9 (5), 457–465. https://doi.org/10.1038/nchem.2695.(5) Yoo, J. S.; Rong, X.; Liu, Y.; Kolpak, A. M. Role of Lattice Oxygen Participation in Understanding Trends in the Oxygen Evolution Reaction on Perovskites. ACS Catal. 2018, 8 (5), 4628–4636. https://doi.org/10.1021/acscatal.8b00612.

Minimal doping approach to activate lattice oxygen participation in K2WO4 electrocatalysts for oxygen evolution reaction

Understanding oxygen redox processes is pivotal for advancing oxygen evolution catalysts, critical in electrochemical devices for renewable fuel synthesis. Thermodynamic instability of high entropy metal oxides can interfere with oxygen redox reactions via electrochemical reconstruction. Transforming a W5N4 pre-catalyst into thermodynamically stable K2WO4 through electrochemical treatment in KOH, and incorporating minimal Fe doping, modifies the oxygen evolution reaction (OER) pathway towards oxygen redox activity, significantly influenced by the pH of the electrolyte. The Fe-doped K2WO4 catalyst demonstrates superior OER performance, achieving 10 mA/cm^2 at an overpotential of merely 181 mV (without iR compensation) and sustaining a lifetime of 1200 h at 1000 mA/cm2. Electrochemical methods and DFT calculations confirmed Fe doping creates oxygen vacancies and increases electron density near the Fermi level, enhancing the OER pathway. This methodology offers a versatile approach to adapt high entropy catalysts for broad electrochemical energy conversion applications, highlighting its potential for innovation in renewable energy technologies.

Bimetal (CuNi and CuCo) substituted CeO2: An approach for low temperature dry reforming of methane

The solution combustion synthesis method was used to make CuNi substituted CeO2 (7.5 at.% of Cu+7.5 at.% of Ni), and CuCo substituted CeO2 (7.5 at.% of Cu+7.5 at.% of Co) catalysts. The catalysts were characterized by x-ray diffraction (XRD),XPS, BET surface area measurements, scanning electron microscopy (SEM), and H2-temperature-programmed reduction(H2-TPR). Further, these catalysts were tested for endothermic dry reforming of methane (DRM) reaction. The CuNi substituted CeO2 catalyst started dry reforming of methane (DRM) at around 350 °C, while the CuCo substituted CeO2 catalyst started DRM at around 450 °C. This indicates that the CuNi catalyst has a lower activation temperature for the DRM reaction compared to the CuCo catalyst. The CuNi substituted CeO2 catalyst converted CH4 better than the CuCo substituted CeO2 at all temperatures reaching 98 % conversion at 800 °C The CuNi substituted CeO2 showed higher H2/CO ratio in comparison to the CuCo substituted CeO2 but the long-term stability followed the opposite order. Thermal gravimetric analysis (TGA), SEM and O2-TPO were used to quantify as well as to understand the nature of carbon that had built up on spent catalysts and it is mostly amorphous. Transient studies have shown that along with the lattice oxygen participation, controlled methane decomposition step is necessary for stability of catalysts. Transient studies also recommended additional reaction steps during DRM where an exothermic methane partial oxidation step reduces the endothermicity of DRM. Also, CO2 activation also goes via the defect dissociation route, an additional step to the conventional carbon oxidation (CO2+C→CO) step. So, novelty of this work is in elucidating the exact role of lattice oxygen in imparting the activity and stability to the DRM catalyst.

Pourbaix Machine Learning Framework Identifies Acidic Water Oxidation Catalysts Exhibiting Suppressed Ruthenium Dissolution.

The demand for green hydrogen has raised concerns over the availability of iridium used in oxygen evolution reaction catalysts. We identify catalysts with the aid of a machine learning-aided computational pipeline trained on more than 36,000 mixed metal oxides. The pipeline accurately predicts Pourbaix decomposition energy (Gpbx) from unrelaxed structures with a mean absolute error of 77 meV per atom, enabling us to screen 2070 new metallic oxides with respect to their prospective stability under acidic conditions. The search identifies Ru0.6Cr0.2Ti0.2O2 as a candidate having the promise of increased durability: experimentally, we find that it provides an overpotential of 267 mV at 100 mA cm-2 and that it operates at this current density for over 200 h and exhibits a rate of overpotential increase of 25 μV h-1. Surface density functional theory calculations reveal that Ti increases metal-oxygen covalency, a potential route to increased stability, while Cr lowers the energy barrier of the HOO* formation rate-determining step, increasing activity compared to RuO2 and reducing overpotential by 40 mV at 100 mA cm-2 while maintaining stability. In situ X-ray absorption spectroscopy and ex situ ptychography-scanning transmission X-ray microscopy show the evolution of a metastable structure during the reaction, slowing Ru mass dissolution by 20× and suppressing lattice oxygen participation by >60% compared to RuO2.

Metallic Ru─Ru Interaction in Ruthenium Oxide Enabling Durable Proton Exchange Membrane Water Electrolysis.

Developing efficient and robust electrocatalysts toward the oxygen evolution reaction (OER) is critical for proton exchange membrane water electrolysis (PEMWE). RuO2 possesses intrinsically high OER activity, but the concurrent electrochemical dissolution leads to rapid deactivation. Here a unique RuO2 catalyst containing metallic Ru─Ru interactions (m-RuO2) is reported, which maintains stability in practical PEMWE for 100h at 60 °C and 1 A cm-2. Experimental and theoretical investigations suggest that the presence of Ru─Ru interactions significantly increases the energy barrier for the formation of RuO2(OH)2, which is a key intermediate for Ru dissolution, and hence substantially mitigates the electrochemical corrosion of m-RuO2. Meanwhile, the Ru4d band center downshifts, accordingly, ensuring the high OER activity, and the participation of lattice oxygen in the OER is also suppressed at the Ru─Ru sites, further contributing to the enhanced durability. Interestingly, such enhanced stability is also dependent on the size of metallic Ru─Ru cluster, where the energy barrier is further increased for Ru3, but is decreased for Ru5. These results highlight the significance of local coordination structure modulation on the electrochemical stability of RuO2 and open a feasible avenue toward the development of robust OER electrocatalysts for high-performance PEMWE.

Dual Doping of B and Fe Activated Lattice Oxygen Participation for Enhanced Oxygen Evolution Reaction Activity in Alkaline Freshwater and Seawater

AbstractThe exploitation of highly activity oxygen evolution reaction (OER) electrocatalysts is critical for the application of electrocatalytic water splitting. Triggering the lattice oxygen mechanism (LOM) is expected to provide a promising pathway to overcome the sluggish OER kinetics, however, effectively enhancing the involvement of lattice oxygen remains challenging. In this study, the fabrication of B, Fe co‐doped CoP (B, Fe─CoP) nanofibers is reported, which serve as highly efficient OER electrocatalyst through phosphorization and boronation treatment of Fe‐doped Co3O4 nanofibers. Experimental results combined with theoretical calculations reveal that simultaneous incorporation of both B and Fe can more effectively trigger the participation of lattice oxygen in CoFe oxyhydroxides reconstructed from B, Fe─CoP nanofibers compared to incorporating only B or Fe. Therefore, the optimized B, Fe─CoP nanofibers exhibit superb OER activity with low overpotentials of 361 and 376 mV at 1000 mA cm−2 in alkaline freshwater and alkaline natural seawater, respectively. The present work provides significant guidelines and innovative design concepts for the development of OER electrocatalysts following the LOM pathway.

Regulating the electronic state of SnO2@NiFe-LDH heterojunction: Activating lattice oxygen for efficient oxygen evolution reaction

In Oxygen Evolution Reaction (OER), catalysts with lattice oxygen, utilizing the Lattice Oxygen Mechanism (LOM), directly participate in oxygen evolution, effectively reducing activation energy. NiFe-Layered Double Hydroxides (NiFe-LDHs), rich in surface hydroxyls, are potential for LOM. However, their stability is challenged in alkaline conditions due to metal cation dissolution from the lattice, limiting catalytic efficiency. In this work, we modify NiFe-LDH by combining hydrothermal and electrodeposition techniques, coupling NiFe-LDH with the metal oxide SnO2. This process creates a heterojunction enriched with oxygen vacancies through interfacial and defect engineering. In 1 M KOH solution, this modified catalyst exhibits an OER overpotential of just 209 mV at a current density of 10 mA cm−2. Furthermore, when the current density is increased to 100 mA cm−2, the overpotential only increases by a modest 46 mV. Subsequent DFT investigations reveal that in the heterostructured system, there is an enhanced overlap between the O 2p and metal 3d orbitals, which optimizes the covalency of the metal–oxygen bond and promotes the participation of lattice oxygen in the reduction reaction. The heterojunction, in concert with oxygen vacancies, aligns the energy bands of oxygen and metal closer to the Fermi level, resulting in improved continuity of electronic orbitals near the Fermi level. This synergistic arrangement significantly reduces the energy barrier for the rate-determining step of the OER, substantiating the improved performance and activation of lattice oxygen.

Oxygen Radical Coupling on Short-Range Ordered Ru Atom Arrays Enables Exceptional Activity and Stability for Acidic Water Oxidation.

The discovery of efficient and stable electrocatalysts for oxygen evolution reaction (OER) in acid is vital for the commercialization of the proton-exchange membrane water electrolyzer. In this work, we demonstrate that short-range Ru atom arrays with near-ideal Ru-Ru interatomic distances and a unique Ru-O hybridization state can trigger direct O*-O* radical coupling to form an intermediate O*-O*-Ru configuration during acidic OER without generating OOH* species. Further, the Ru atom arrays suppress the participation of lattice oxygen in the OER and the dissolution of active Ru. Benefiting from these advantages, the as-designed Ru array-Co3O4 electrocatalyst breaks the activity/stability trade-off that plagues RuO2-based electrocatalysts, delivering an excellent OER overpotential of only 160 mV at 10 mA cm-2 in 0.5 M H2SO4 and outstanding durability during 1500 h operation, representing one of the best acid-stable OER electrocatalysts reported to date. 18O-labeled operando spectroscopic measurements together with theoretical investigations revealed that the short-range Ru atom arrays switched on an oxide path mechanism (OPM) during the OER. Our work not only guides the design of improved acidic OER catalysts but also encourages the pursuit of short-range metal atom array-based electrocatalysts for other electrocatalytic reactions.

Tailoring atomic chemistry to refine reaction pathway for the most enhancement by magnetization in water oxidation

Water oxidation on magnetic catalysts has generated significant interest due to the spin-polarization effect. Recent studies have revealed that the disappearance of magnetic domain wall upon magnetization is responsible for the observed oxygen evolution reaction (OER) enhancement. However, an atomic picture of the reaction pathway remains unclear, i.e., which reaction pathway benefits most from spin-polarization, the adsorbent evolution mechanism, the intermolecular mechanism (I2M), the lattice oxygen-mediated one, or more? Here, using three model catalysts with distinguished atomic chemistries of active sites, we are able to reveal the atomic-level mechanism. We found that spin-polarized OER mainly occurs at interconnected active sites, which favors direct coupling of neighboring ligand oxygens (I2M). Furthermore, our study reveals the crucial role of lattice oxygen participation in spin-polarized OER, significantly facilitating the coupling kinetics of neighboring oxygen radicals at active sites.

Directed Surface Reconstruction of Fe Modified Co2VO4 Spinel Oxides for Water Oxidation Catalysts Experiencing Self-Terminating Surface Deterioration.

Affordable highly efficient catalysts for electrochemical oxygen evolution reaction (OER) play pivotal roles in green hydrogen production via water electrolysis. Regarding the non-noble metal-based electrocatalysts, considerable efforts are made to decipher the cation leaching and surface reconstruction; yet, little attention is focused on correlating them with catalytical activity and stability. Herein, in situ reconstruction of Fe-modified Co2VO4 precursor catalyst to form a highly active (Fe,V)-doped CoOOH phase for OER is reported, during which partial leaching of V accelerates the surface reconstruction and the V reserved in the reconstructed CoOOH layer in the form of alkali-resistant V2O3 serves for dynamic charge compensation and prevention of excessive loss of lattice oxygen and Co dissolution. Fe substitution facilitates Co pre-oxidation and endows the catalysts with structural flexibility by elevating O 2p band level; hence, encouraging participation of lattice oxygen in OER. The optimized Co2Fe0.25V0.75O4 electrode can afford current densities of 10 and 500 mA cm-2 at low overpotentials of 205 and 320 mV, respectively, with satisfactory stability over 600 h. By coupling with Pt/C cathode, the assembled alkaline electrolyzer can deliver 500 mA cm-2 at a low cell voltage of 1.798 V, better than that of commercial RuO2 (+) || Pt/C (-).

Introducing phosphorus into spinel nickel ferrite to enhance lattice oxygen participation towards water oxidation electrocatalysis

Oxygen evolution reaction (OER) restricts the efficiency of overall water splitting due to its complex transfer process and sluggish intrinsic kinetics. The novel lattice oxygen oxidation mechanism (LOM) could lift the theoretical scaling limits of the traditional adsorbate evolution mechanism (AEM), but increasing the participation of lattice oxygen still remains a great challenge. Herein, we introduce phosphorus into spinel nickel ferrite as electrocatalyst with an overpotential of 264 mV at 10 mA cm−2 towards water oxidation. Experimental results confirm the enhanced participation of lattice oxygen for OER in P-NiFe2O4. Further theoretical modelling reveals that the incorporated phosphorus results in an upshift of O 2p band center relative to Fermi level and enhances hybridization of the metal-oxygen bond, thus facilitating LOM and accelerating the OER process on spinel NiFe2O4. This work provides some deep insights into the OER mechanism and a sound strategy for improving the electrocatalytic activity of spinel oxides.

Essential role of lattice oxygen in hydrogen sensing reaction.

Understanding the sensing mechanism of metal oxide semiconductors is imperative to the development of high-performance sensors. The traditional sensing mechanism only recognizes the effect of surface chemisorbed oxygen from the air but ignores surface lattice oxygen. Herein, using in-situ characterizations, we provide direct experimental evidence that the surface chemisorbed oxygen participated in the sensing process can come from lattice oxygen of the oxides. Further density functional theory (DFT) calculations prove that the p-band center of O serves as a state of art for regulating the participation of lattice oxygen in gas-sensing reactions. Based on our experimental data and theoretical calculations, we discuss mechanisms that are fundamentally different from the conventional mechanism and show that the easily participation of lattice oxygen is helpful for the high response value of the materials.

Perovskite for Electrocatalytic Oxygen Evolution at Elevated Temperatures.

The development of advanced electrolysis technologies such as anion exchange membrane water electrolyzer (AEMWE) is central to the vision of a sustainable energy future. Key to the realization of such AEMWE technology lies in the exploration of low-cost and high-efficient catalysts for facilitating the anodic oxygen evolution reaction (OER). Despite tremendous efforts in the fundamental research, most of today's OER works are conducted under room temperature, which deviates significantly with AEMWE's operating temperature (50-80 °C). To bridge this gap, it is highly desirable to obtain insights into the OER catalytic behavior at elevated temperatures. Herein, using the well-known perovskite catalyst Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) as a proof of concept, the effect of temperature on the variation in OER catalytic activity and stability is evaluated. It is found that the BSCF's activity increases with increasing temperature due to enhanced lattice oxygen participation promoting the lattice oxygen-mediated OER process. Further, surface amorphization and cation leaching of BSCF become more pronounced as temperature increases, causing a somewhat attenuated OER stability. These new understandings of the fundamental OER catalysis over perovskite materials at industrial-relevant temperature conditions are expected to have strong implications for the research of OER catalysts to be deployed in practical water electrolyzers.

P-Incorporation Induced Enhancement of Lattice Oxygen Participation in Double Perovskite Oxides to Boost Water Oxidation.

Activating the lattice oxygen in the catalysts to participate in the oxygen evolution reaction (OER), which can break the scaling relation-induced overpotential limitation (> 0.37V) of the adsorbate evolution mechanism, has emerged as a new and highly effective guide to accelerate the OER. However, how to increase the lattice oxygen participation of catalysts during OER remains a major challenge. Herein, P-incorporation induced enhancement of lattice oxygen participation in double perovskite LaNi0.58Fe0.38P0.07O3-σ (PLNFO) is studied. P-incorporation is found to be crucial for enhancing the OER activity. The current density reaches 1.35mA cmECSA -2 at 1.63V (vs RHE), achieving a sixfold increase in intrinsic activity. Experimental evidences confirm the dominant lattice oxygen participation mechanism (LOM) for OER pathway on PLNFO. Further electronic structures reveal that P-incorporation shifts the O p-band center by 0.7eV toward the Fermi level, making the states near the Fermi level more O p character, thus facilitating LOM and fast OER kinetics. This work offers a possible method to develop high-performance double perovskite OER catalysts for electrochemical water splitting.

Strain‐modulated Ru‐O Covalency in Ru‐Sn Oxide Enabling Efficient and Stable Water Oxidation in Acidic Solution

AbstractRuO2 is one of the benchmark electrocatalysts used as the anode material in proton exchange membrane water electrolyser. However, its long‐term stability is compromised due to the participation of lattice oxygen and metal dissolution during oxygen evolution reaction (OER). In this work, weakened covalency of Ru−O bond was tailored by introducing tensile strain to RuO6 octahedrons in a binary Ru−Sn oxide matrix, prohibiting the participation of lattice oxygen and the dissolution of Ru, thereby significantly improving the long‐term stability. Moreover, the tensile strain also optimized the adsorption energy of intermediates and boosted the OER activity. Remarkably, the RuSnOx electrocatalyst exhibited excellent OER activity in 0.1 M HClO4 and required merely 184 mV overpotential at a current density of 10 mA cm−2. Moreover, it delivered a current density of 10 mA cm−2 for at least 150 h with negligible potential increase. This work exemplifies an effective strategy for engineering Ru‐based catalysts with extraordinary performance toward water splitting.

Strain-modulated Ru-O Covalency in Ru-Sn Oxide Enabling Efficient and Stable Water Oxidation in Acidic Solution.

RuO2 is one of the benchmark electrocatalysts used as the anode material in proton exchange membrane water electrolyser. However, its long-term stability is compromised due to the participation of lattice oxygen and metal dissolution during oxygen evolution reaction (OER). In this work, weakened covalency of Ru-O bond was tailored by introducing tensile strain to RuO6 octahedrons in a binary Ru-Sn oxide matrix, prohibiting the participation of lattice oxygen and the dissolution of Ru, thereby significantly improving the long-term stability. Moreover, the tensile strain also optimized the adsorption energy of intermediates and boosted the OER activity. Remarkably, the RuSnOx electrocatalyst exhibited excellent OER activity in 0.1 M HClO4 and required merely 184 mV overpotential at a current density of 10 mA cm-2 . Moreover, it delivered a current density of 10 mA cm-2 for at least 150 h with negligible potential increase. This work exemplifies an effective strategy for engineering Ru-based catalysts with extraordinary performance toward water splitting.

Lattice Oxygen Exchange in Transition Metal Oxyhydroxides and Metal Hydroxide Organic Frameworks Elucidated for the Oxygen Evolution Reaction

To achieve the goal of climate neutrality by 2050, it is essential to increase the use of renewable fuels and carbon-neutral energy.1 The anodic oxygen evolution reaction (OER) is a key reaction not only in electrocatalytic production of many renewable fuels,2 but also for next generation of charge storage devices such as metal-air batteries.3 However, the slow kinetics of the OER process result in high energy losses and costs.4 Therefore, the development of more efficient electrocatalysts is critical for making renewable energy via electrocatalysis a viable option in emerging energy systems.Transition metal (TM) oxides are a promising alternative to expensive noble metals due to their high catalytic OER activity under alkaline conditions and wider earth-abundance. Despite extensive research, establishing structure-activity correlations and understanding mechanistic processes is challenging, given the intricate interplay between external and intrinsic parameters.In this study, we investigate the role of lattice oxygens in electrodeposited Ni-Fe, Co-Fe, and Mn-Fe oxyhydroxide (M(OH)xOy, M = TM) electrocatalysts using surface-enhanced Raman spectroscopy (SERS) in conjunction with secondary ion mass spectroscopy (SIMS). By taking advantage of the Raman shift that results from 16O/18O isotope exchange,5–7 we can track the participation of lattice oxygens in the electrocatalytic cycle. Our investigation reveals that, during OER, all the electrocatalysts display minimal exchange of lattice oxygens with the electrolyte (less than 5%). However, many of these electrocatalysts show partial or complete exchange when exposed to non-catalytic potential when in their more reduced states (see Figure 1).Apart from fully inorganic catalysts, we also present results from Ni-derived metal-hydroxide-organic frameworks (MHOFs), which are analogous to M(OH)xOy catalysts but with organic linkers separating the layers.8 Our findings indicate that MHOFs with linkers that have a high π-π stacking energy (and a high structural stability)8 undergo near complete 16O/18O exchange during OER, while MHOFs employing linkers with a low π-π stacking energy (and thus a low stability) show minor or no lattice exchange during OER.Our study suggests that participation oflattice oxygens is closely linked to the oxidation state of the transition metals rather than to the catalytic process. The work provides a detailed picture of the exchange mechanism and elucidates alternative processes involved in lattice oxygen participation and discusses their relation to the mechanisms of the OER process. References IEA (2023), Energy Technology Perspectives 2023, IEA, Paris https://www.iea.org/reports/energy-technology-perspectives-2023, License: CC BY 4.0.Wei, S. Z. et al. Combining theory and experiment in electrocatalysis: Insights into materials design. Science (80-. ). 355, eaad4998 (2017).Li, Y. & Lu, J. Metal–Air Batteries: Will They Be the Future Electrochemical Energy Storage Device of Choice? ACS Energy Lett. 2, 1370–1377 (2017).Song, F. et al. Transition Metal Oxides as Electrocatalysts for the Oxygen Evolution Reaction in Alkaline Solutions: An Application-Inspired Renaissance. J. Am. Chem. Soc. 140, 7748–7759 (2018).Lee, S., Banjac, K., Lingenfelder, M. & Hu, X. Oxygen Isotope Labeling Experiments Reveal Different Reaction Sites for the Oxygen Evolution Reaction on Nickel and Nickel Iron Oxides. Angew. Chemie Int. Ed. 58, 10295–10299 (2019).Moysiadou, A., Lee, S., Hsu, C.-S., Chen, H. M. & Hu, X. Mechanism of Oxygen Evolution Catalyzed by Cobalt Oxyhydroxide: Cobalt Superoxide Species as a Key Intermediate and Dioxygen Release as a Rate-Determining Step. J. Am. Chem. Soc. 142, 11901–11914 (2020).Diaz-Morales, O., Ferrus-Suspedra, D. & Koper, M. T. M. The importance of nickel oxyhydroxide deprotonation on its activity towards electrochemical water oxidation. Chem. Sci. 7, 2639–2645 (2016).Yuan, S. et al. Tunable metal hydroxide–organic frameworks for catalysing oxygen evolution. Nat. Mater. 21, 673–680 (2022). Figure 1

Carbon Monoxide Oxidation on Ceria-Supported Nanoclusters.

Periodic density functional theory is used to evaluate the minimum energy pathways of CO oxidation on cerium oxide-supported platinum and palladium nanoclusters (Pt/CeO2 and Pd/CeO2). For Pt/CeO2, the oxidation process involves the participation of lattice oxygen from CeO2 at the boundary sites of the cluster-ceria interface, which exhibits an exceptionally low energy barrier. Conversely, on Pd/CeO2, oxidation predominantly occurs through oxygen species bound to the Pd cluster. Experimental analysis using the temperature-programmed reduction of the oxidized Pd/CeO2 catalyst reveals a lower CO oxidation temperature compared to Pt/CeO2. This observation aligns with the anticipated decrease in the energy barrier for CO oxidation due to the oxygen coverage of the Pd cluster.

Essential role of lattice oxygen in methanol electrochemical refinery toward formate.

Developing technologies based on the concept of methanol electrochemical refinery (e-refinery) is promising for carbon-neutral chemical manufacturing. However, a lack of mechanism understanding and material properties that control the methanol e-refinery catalytic performances hinders the discovery of efficient catalysts. Here, using 18O isotope-labeled catalysts, we find that the oxygen atoms in formate generated during the methanol e-refinery reaction can originate from the catalysts' lattice oxygen and the O-2p-band center levels can serve as an effective descriptor to predict the catalytic performance of the catalysts, namely, the formate production rates and Faradaic efficiencies. Moreover, the identified descriptor is consolidated by additional catalysts and theoretical mechanisms from density functional theory. This work provides direct experimental evidence of lattice oxygen participation and offers an efficient design principle for the methanol e-refinery reaction to formate, which may open up new research directions in understanding and designing electrified conversions of small molecules.

Evidence of oxygen evolution over sputtered zinc ferrite (ZnFe2O4) thin film by enhanced lattice oxygen participation

We report evidence of oxygen evolution over zinc ferrite (ZnFe2O4) thin films grown on indium tin oxide and quartz substrates using the RF sputtering. The thin films are deposited at ambient temperature with different argon/oxygen gas ratios, specifically 1:0 (Z–Ar), 1:1 (Z–Ar:O), and 0:1 (Z–O). Structural characterization using grazing incidence x-ray diffraction at a 0.400° grazing angle confirmed the polycrystalline nature of the films. X-ray photoelectron spectroscopy scans of Zn 2p, Fe 2p, and O1s were conducted to investigate the lattice oxygen vacancies. The lattice oxygen vacancies in the Z–Ar film resulted in a lower bandgap of 2.05 eV than the Z–O film of 2.36 eV. The oxygen evolution reaction (OER) performances of the thin films are investigated to understand the effect of oxygen vacancies on electrochemical activity and observed that the Z–Ar film, with oxygen vacancies, exhibits a decrease in overpotential by ∼12.5% at 10 mA cm−2, eightfold increase in current density at 520 mV overpotential deduced from linear sweep voltammetry, and a 71.9% increase in donor density inferred from the Mott–Schottky plot, as compared to the Z–O film. The findings suggest that the Z–Ar film follows a “lattice oxygen participation mechanism” for the OER, instead of an “adsorbate evolution mechanism” observed in the Z–O film. The results highlight the significant impact of argon/oxygen gas ratios on the structural, optical, and electrochemical properties of zinc ferrite thin films and provide insight into the role of oxygen vacancies in modulating the OER performance for potential applications.