Oxidation Of Lattice Oxygen Research Articles

Ex Situ Reconstruction-Shaped Ir/CoO/Perovskite Heterojunction for Boosted Water Oxidation Reaction.

The oxygen evolution reaction (OER) is the performance-limiting step in the process of water splitting. In situ electrochemical conditioning could induce surface reconstruction of various OER electrocatalysts, forming reactive sites dynamically but at the expense of fast cation leaching. Therefore, achieving simultaneous improvement in catalytic activity and stability remains a significant challenge. Herein, we used a scalable cation deficiency-driven exsolution approach to ex situ reconstruct a homogeneous-doped cobaltate precursor into an Ir/CoO/perovskite heterojunction (SCI-350), which served as an active and stable OER electrode. The SCI-350 catalyst exhibited a low overpotential of 240 mV at 10 mA cm-2 in 1 M KOH and superior durability in practical electrolysis for over 150 h. The outstanding activity is preliminarily attributed to the exponentially enlarged electrochemical surface area for charge accumulation, increasing from 3.3 to 175.5 mF cm-2. Moreover, density functional theory calculations combined with advanced spectroscopy and 18O isotope-labeling experiments evidenced the tripled oxygen exchange kinetics, strengthened metal-oxygen hybridization, and engaged lattice oxygen oxidation for O-O coupling on SCI-350. This work presents a promising and feasible strategy for constructing highly active oxide OER electrocatalysts without sacrificing durability.

Comprehensively Strengthened Metal‐Oxygen Bonds for Reversible Anionic Redox Reaction

AbstractIntroducing anionic redox in layered oxides is an effective approach to breaking the capacity limit of conventional cationic redox. However, the anionic redox reaction generally suffers from excessive oxidation of lattice oxygen to O2 and O2 release, resulting in local structural deterioration and rapid capacity/voltage decay. Here, a Na0.71Li0.22Al0.05Mn0.73O2 (NLAM) cathode material is developed by introducing Al3+ into the transition metal (TM) sites. Thanks to the strong Al–O bonding strength and small Al3+ radius, the TMO2 skeleton and the holistic TM–O bonds in NLAM are comprehensively strengthened, which inhibits the excessive lattice oxygen oxidation. The obtained NLAM exhibits a high reversible capacity of 194.4 mAh g‐1 at 20 mA g‐1 and decent cyclability with 98.6% capacity retention over 200 cycles at 200 mA g−1. In situ characterizations reveal that the NLAM experiences phase transitions with an intermediate OP4 phase during the charge–discharge. Theoretical calculations further confirm that the Al substitution strategy is beneficial for improving the overlap between Mn 3d and O 2p orbitals. This finding sheds light on the design of layered oxide cathodes with highly reversible anionic redox for sodium storage.

High-Voltage Layered Manganese-Based Oxide Cathode with Excellent Rate Capability Enabled by K/F Co-doping

P-type layered manganese-based materials are prone to undergo lattice oxygen oxidation accompanied by oxygen layer slipping and even unfavorable phase transitions at around 4.2 V, giving rise to rapid discharge capacity decline and inferior structural stability, which restricts their operating voltage and energy density. Here we propose a modification strategy for layered Na0.67MnO2 material with K/F co-doping so as to reach the optimization of lattice oxygen oxidation behavior and structural stability at a high cut-off voltage of 4.4 V. Combining X-ray powder diffraction refinement results, ex situ X-ray photoelectron spectrometry analysis, high-resolution transmission electron microscopy, and electrochemical characterization, our work demonstrates that an appropriate amount of K/F co-doping has a favorable effect on the formation of well-reversible lattice oxygen oxidation behavior and the improvement of Na layer spacing. Owing to the synergetic effect of potassium and fluorine atoms, the initial discharge capacity is up to 210.2 mA h g–1 at 0.1 C and 140.2 mA h g–1 at 1 C with 73% capacity retention after 100 cycles and high discharge capacity of 115.0 mA h g–1 at 5 C, with 68.1 mA h g–1 retained after 200 cycles. The kinetic analysis shows that the optimal K0.05Na0.62MnO1.95F0.05 sample exhibits the largest sodium ion diffusion coefficient and the smallest electrochemical polarization, which paves a novel path for the application of layered manganese-based oxides in high-voltage cathode materials for sodium-ion batteries.

A new film-forming electrolyte additive in enhancing the interface of layered cathode and cycling life of sodium ion batteries

Sodium layered oxides have been widely investigated as cathodes for sodium-ion batteries (SIBs), and extensive research efforts have been made to enhance their performance through composition design and structural engineering. However, limited attention has been paid to developing the electrolyte system and stabilizing the electrolyte–cathode interface, which play important roles in determining the cycling life of SIBs. Herein, a new electrolyte additive, diglycolic anhydride (DGA), is investigated as a film-forming additive. A Na/Na0.67Li0.2Ni0.23Mn0.67O2 (NLNMO) cell with 2 wt% DGA in the electrolyte exhibits a capacity of 85 mAh g−1 at a rate of 1 C, with a retention of 92.59% after 1000 cycles. Soft X-ray absorption characterization, 18O2 isotopic labeling, titration mass spectrometry, and online electrochemical mass spectrometry measurements are performed. The results reveal that the robust interface formed by DGA inhibits side reactions between the electrolyte and (O2)n– species formed through the oxidation of lattice oxygen, thus resulting in the retention of the original NLNMO cathode structure and a prolonged lifespan in Na/NLNMO batteries. Furthermore, electrochemical impedance spectroscopy using a three-electrode cell system reveals the influence of DGA on the interface at the NLNMO cathode and Na metal anode.

Lattice oxygen activation in disordered rocksalts for boosting oxygen evolution.

The recent development of some special oxygen evolution reaction (OER) electrocatalysts shows that the lattice oxygen could participate in the catalysis process via the lattice oxygen oxidation mechanism (LOM), which the provides good possibility of exploring advanced electrocatalysts that could overcome the scaling relationship in conventional catalysis processes through a traditional adsorbate evolution mechanism. In this work, we theoretically predict that, benefiting from the unhybridized O-Li orbitals and the resulting metastable Li-O-Li ligands, the lattice oxygen could be easily activated and oxidized at relatively high oxidation voltages. Thus, lithium-excess disordered rocksalts (DRX) should possess the potential for acting as active OER electrocatalysts, which catalyze through the LOM pathway. The isotope labelling experimental results show that the lattice oxygen in the DRX was activated and participated in the OER process through the LOM pathway. The typical DRX of Li1.2Fe0.4Ti0.5O2 displays obviously pH-dependent OER activity under the LOM process and shows a low overpotential of 263 mV to reach 10 mA cm-2 with long-term stability for 100 hours. The turnover frequency of Li1.2Fe0.4Ti0.5O2 is nearly 9 times that of LiFePO4 at the overpotential of 300 mV. This work opens a new chemical space for exploring efficient electrocatalysts to enhance the OER performance through the LOM pathway.

O-hetero-Fe-N3.6 active sites in ZIF-derived carbon nanotubes for the electrocatalytic oxygen evolution reaction

In order to clarify competitive reactions between lattice oxygen oxidation mechanism (LOM) with lower energy barrier and conventional adsorbate evolution mechanism (AEM), O-hetero-Fe-N3.6 active site was built in ZIF-derived carbon nanotubes to transform traditional AEM mechanism on iron-unsaturated active site into LOM mechanism during electrocatalytic oxygen evolution reaction (OER). In-situ attenuated total reflectance infrared (ATR-FTIR) and X-ray absorption fine structure results confirmed the formation of Fe-O bonds and a Fe-N3.6 structure, indicating that O-hetero-Fe-N3.6 active sites were built. A key intermediate O* was detected on ATR-FTIR, which suggests that OER proceeded via LOM mechanism. The alkaline OER activity and stability are enhanced on the O-hetero-Fe-N3.6 active sites to accelerate rate-determining step of water oxidation. The ZIF-derived carbon nanotubes expose more O-hetero-Fe-N3.6 active sites to facilitate electron and mass transfer during electrocatalytic OER. The Fe-NC catalyst exhibits excellent OER activity with an overpotential of 235 mV at 10 mA cm−2 and Tafel slope of 98 mV dec−1 in 1 M KOH.

Understanding of Oxygen Redox in the Oxygen Evolution Reaction.

The electron-transfer process during the oxygen evolution reaction (OER) often either proceeds solely via a metal redox chemistry (adsorbate evolution mechanism (AEM), with metal bands around the Fermi level) or an oxygen redox chemistry (lattice oxygen oxidation mechanism (LOM), with oxygen bands around the Fermi level). Unlike the AEM, the LOM involves oxygen redox chemistry instead of metal redox, which leads to the formation of a direct oxygen-oxygen (OO) bond. As a result, such a process is able to bypass the rate-determining step, that is, OO bonding, in AEM, which highlights the critical advantage of LOM as compared to the conventional AEM. Thus, it has been well reported that LOM-based catalysts are able to demonstrate higher OER activities as compared to AEM-based catalysts. Here, a comprehensive understanding of the oxygen redox in LOM and all documented and possible characterization techniques that can be used to identify the oxygen redox are reviewed. This review will interpret the origins of oxygen redox in the reported LOM-based electrocatalysts and the underlying science of LOM-induced surface reconstruction in transition metal oxides. Finally, perspectives on the future development of LOM electrocatalysts are also provided.

Activated Ni-O-Ir Enhanced Electron Transfer for Boosting Oxygen Evolution Reaction Activity of LaNi1-x Irx O3.

Tuning the structure of the active center of catalysts to atomic level provides the most efficient utilization of the active component, which plays an especially important role for precious metals. In this study, the liquid phase ion exchange method is used to introduce atomic Ir into LaNiO3 perovskite oxide, which shows excellent catalytic performance in the oxygen evolution reaction (OER). The catalyst, LaNi0.96 Ir0.04 O3 , with the optimal concentration of Ir, displays an overpotential of just 280mV at 10mAcm-2 . The introduced Ir enriches the surface electron density significantly, which not only improves site-to-site electron transfer between O and Ni sites but also allows stable adsorption of the intermediates. Theresults of cyclic voltammetry tests reveal the superior overpotential and remarkable efficiency of the OER process because of the strong interactions in Ni-O-Ir. Moreover, the Ir atom inhibits the participation of a lattice oxygen oxidation mechanism (LOM) in LaNiO3 that guarantees the stability of the catalyst in alkaline conditions. It is anticipated that this work will be instrumental for the preparation and study of a broad range of atomic metal-doped perovskite oxides for water splitting.

Pivotal role of reversible NiO6 geometric conversion in oxygen evolution.

Realizing an efficient electron transfer process in the oxygen evolution reaction by modifying the electronic states around the Fermi level is crucial in developing high-performing and robust electrocatalysts1-3. Typically, electron transfer proceeds solely through either a metal redox chemistry (an adsorbate evolution mechanism (AEM), with metal bands around the Fermi level) or an oxygen redox chemistry (a lattice oxygen oxidation mechanism (LOM), with oxygen bands around the Fermi level), without the concurrent occurrence of both metal and oxygen redox chemistries in the same electron transfer pathway1-15. Here we report an electron transfer mechanism that involves a switchable metal and oxygen redox chemistry in nickel-oxyhydroxide-based materials with light as the trigger. In contrast to the traditional AEM and LOM, the proposed light-triggered coupled oxygen evolution mechanism requires the unit cell to undergo reversible geometric conversion between octahedron (NiO6) and square planar (NiO4) to achieve electronic states (around the Fermi level) with alternative metal and oxygen characters throughout the oxygen evolution process. Utilizing this electron transfer pathway can bypass the potential limiting steps, that is, oxygen-oxygen bonding in AEM and deprotonation in LOM1-5,8. As a result, the electrocatalysts that operate through this route show superior activity compared with previously reported electrocatalysts. Thus, it is expected that the proposed light-triggered coupled oxygen evolution mechanism adds a layer of understanding to the oxygen evolution research scene.

Regulating Ru-based double perovskite against lattice oxygen oxidation by incorporating Ir for efficient and stable acidic oxygen evolution reaction

Oxygen evolution reaction is one of the core half-reactions in proton-exchange membrane (PEM) water electrolysis, but its slow reaction kinetics has been limiting the overall energy conversion efficiency (e.g., water splitting). It is urgent to develop efficient catalysts for OER in acidic media. At present, Ru-based catalysts have high activity, but their poor stability makes them difficult to be used in acidic oxygen evolution reactions. The involvement of lattice oxygen mechanism (LOM) in the reaction is one of the main causes of instability in Ru-based catalysts. Herein, we synthesized SrRu0.5Ir0.5O3 double perovskite by doping Ir into SrRuO3. The double perovskite displays an extraordinary OER performance with a low overpotential of 185 mV at 10 mA cm−2 current density and maintains its catalytic stability for over 50 h in 0.5 M H2SO4. X-ray photoelectron spectroscopy results show that the electronic synergistic effect between Ir and Ru enables the double perovskite materials with high activity. Meanwhile, the double perovskite catalyst inhibits the occurrence of the lattice oxygen mechanism during the OER, which greatly improve the catalytic stability of Ru-based perovskite materials.

Dynamics of Both Active Phase and Catalysis Pathway for Spinel Water‐Oxidation Catalysts

AbstractThe active structure and catalysis pathway of catalytic materials jointly dominate the thermodynamic energy barrier and kinetic rate during the reactions, which severely restrict their catalysis service behaviors. Herein, the whole dynamic process covering both the structural evolution and the catalysis pathway evolution of model catalyst spinel NiCo2O4 during water oxidation via in situ experiments and theoretical calculations is investigated. Based on the identified authentic terminated active phase NiOOH and figured lattice oxygen oxidation pathway, an effective expedition and optimization of this reconfiguration with a proper doping approach is sufficiently evidenced, to finally establish a life‐time dynamic structure–performance correlation of catalysts and acquire outstanding catalysis activity. Results indicate synergistic deliberation of two critical issues regarding the dynamics of both catalyst structure and catalysis pathway can truthfully benefit the in‐depth understanding of advanced catalysts design and render their performance.

Constructing high-activity Cobalt‐based Perovskite hybrid by a top-down phase evolution method for the direct seawater electrolysis anode

The direct seawater electrolysis requires the robust oxygen evolution reaction (OER) catalysts with high activity and stability. Co-based perovskites with superior durability can be used as the promising OER catalysts for the direct seawater electrolysis, though their OER catalytic activity still needs to be improved. In this work, we propose a novel top-down phase evolution method to synthesize a Co-based perovskite hybrid (P/RP-SNCF) compositing the ABO3-type SrNb0.1Co0.7Fe0.2O3-δ (P-SNCF) and Ruddlesden-Popper Sr3NbCoO7-δ (RP-SNCF) perovskite by a facile annealing method. Compared with P-SNCF, the OER process of P/RP-SNCF prefers the lattice oxygen oxidation (LOM) pathway. The P/RP-SNCF hybrid shows significantly enhanced OER catalytic activity with the overpotential being as low as 335 mV at 10 mA cm-2. By the active surface reconstruction of P/RP-SNCF with electrochemical reduction, the optimized ER-P/RP-SNCF-5 shows the further improved OER activity. Furthermore, by using ER-P/RP-SNCF-5 as the anode for the direct seawater electrolysis, the electrolytic voltage reaches 1.57 V to yield a current density of 10 mA cm-2 and keeps stable for 100 h. The proposed strategy provides a new insight into the design of the high-performance perovskite hybrid for the direct seawater electrolysis.

Artificially steering electrocatalytic oxygen evolution reaction mechanism by regulating oxygen defect contents in perovskites.

The regulation of mechanism on the electrocatalysis process with multiple reaction pathways is more efficient and essential than conventional material engineering for the enhancement of catalyst performance. Here, by using oxygen evolution reaction (OER) as a model, which has an adsorbate evolution mechanism (AEM) and a lattice oxygen oxidation mechanism (LOM), we demonstrate a general strategy for steering the two mechanisms on various LaxSr1−xCoO3−δ. By delicately controlling the oxygen defect contents, the dominant OER mechanism on LaxSr1−xCoO3−δ can be arbitrarily transformed between AEM-LOM-AEM accompanied by a volcano-type activity variation trend. Experimental and computational evidence explicitly reveal that the phenomenon is due to the fact that the increased oxygen defects alter the lattice oxygen activity with a volcano-type trend and preserve the Co0 state for preferably OER. Therefore, we achieve the co-optimization between the activity and stability of catalysts by altering the mechanism rather than a specific design of catalysts.

Enhancing cycling stability in Li-rich Mn-based cathode materials by solid-liquid-gas integrated interface engineering

The specific capacity of Li-rich Mn-based cathode materials (LRM) can be enhanced by the oxidation of lattice oxygen at high voltages. Nevertheless, an irreversible oxygen loss emerges with cycling, triggering interlocking surface/interface issues and thereby the fast deterioration of cycling performance. Herein, a solid-liquid-gas integrated surface/interface modification method is presented to form a CEI preconstruction layer and defective heterostructure on the surface/interface of LRM material to improve its cycling stability greatly. The CEI preconstruction layer can effectively anchor on the surface/interface of LRM primary and secondary particles to induce a thin and exceptionally stable CEI layer during cycling, and then mitigate the TM dissolution and strengthen the stability of surface lattice oxygen. The introduced defective heterostructure can reduce the charge transfer resistance. As a result, the designed LRM cathode displays a high reversible capacity of 315 mAh g−1 at 0.1 C as well as high capacity retention of 83.3% at 1 C after 500 cycles. Outstanding voltage stability with a retention of 91.5% is achieved at 5 C after 500 cycles. This work opens an attractive path in manipulating the surface/interface stability of LRM to enhance its cycling performance for high-energy-density Li-ion batteries.

Redirecting dynamic structural evolution of nickel-contained RuO2 catalyst during electrochemical oxygen evolution reaction

Electrochemical oxygen evolution reaction (OER) is a main efficiency bottleneck of water electrolysis. Commercial ruthenium oxide (RuO2) catalyst displays remarkable activities but poor stability for OER. The instability stems from lattice oxygen oxidation, resulting in the oxidation of Ru4+ to soluble Rux+ (x > 4) species. Herein, we redirect dynamic structural evolution of Ru-based catalysts through introducing oxidized nickel (Ni) components. By virtue of comprehensive structural characterizations, such as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), operando Raman and so forth, it is demonstrated that when the atomic content of Ni exceeds that of ruthenium (Ru), the Ni components can efficiently inhibit the Ru4+ oxidation and structural collapse. Density functional theory (DFT) calculations suggest that the introduction of Ni component hinders the formation of oxygen vacancies, and makes lattice oxygen mediated mechanism turn to adsorbate evolution mechanism, which eventually improves the stability. The optimized nickel-contained RuO2 catalyst delivers an effective reactivity with an overpotential of less than 215 mV to attain 10 mA cm−2 and remarkable stability with only 5 mV increment after 5000 potential cycles. This work provides insights into the origin of dynamic structural evolution of transition-metal-modified RuO2 electrocatalysts.

Key roles of surface Fe sites and Sr vacancies in the perovskite for an efficient oxygen evolution reactionvialattice oxygen oxidation

Highly efficient La/Sr-based perovskites with surface Fe sites and Sr vacancies were developed for the active lattice oxygen mechanism (LOM) of the oxygen evolution reaction (OER), and a relationship between the LOM and dynamic surface structure was established.

Safeguarding the RuO2 phase against lattice oxygen oxidation during acidic water electrooxidation

Pt impregnated into the RuO2 phase assisted by oxophilic Co suppresses the over-oxidation of Ru during water electrooxidation under acidic conditions.

Activating the lattice oxygen oxidation mechanism in amorphous molybdenum cobalt oxide nanosheets for water oxidation

Amorphous ultrathin MoCoxOynanosheets with excellent OER catalytic performance were prepared, and the incorporation of molybdenum to enable a lattice oxygen oxidation mechanism (LOM).

Oxygen evolution in spin-sensitive pathways

The overall performance of water electrolysis suffers from the high kinetic barrier in the oxygen evolution reaction (OER) at the anode. Considerable effort has been made on the fundamental understandings of the reaction mechanisms of OER. Recently, the attention has been given to the OER on magnetic catalysts, which is believed being able to promote the kinetics of an OER process from singlet reactants to triplet oxygen. The process in principle involves spin selective electron transfer. Here, we discuss the effects of spin in OER based on the recent advances and summarize our recently proposed mechanisms of the OER in spin-sensitive pathways under the lattice oxygen oxidation mechanism, the interaction of two M−O entity mechanism, and the adsorbate evolution mechanism.

Engineering Lattice Oxygen Activation of Iridium Clusters Stabilized on Amorphous Bimetal Borides Array for Oxygen Evolution Reaction.

Developing robust oxygen evolution reaction (OER) catalysts requires significant advances in material design and in-depth understanding for water electrolysis. Herein, we report iridium clusters stabilized surface reconstructed oxyhydroxides on amorphous metal borides array, achieving an ultralow overpotential of 178 mV at 10 mA cm-2 for OER in alkaline medium. The coupling of iridium clusters induced the formation of high valence cobalt species and Ir-O-Co bridge between iridium and oxyhydroxides at the atomic scale, engineering lattice oxygen activation and non-concerted proton-electron transfer to trigger multiple active sites for intrinsic pH-dependent OER activity. The lattice oxygen oxidation mechanism (LOM) was confirmed by in situ 18 O isotope labeling mass spectrometry and chemical recognition of negative peroxo-like species. Theoretical simulations reveal that the OER performance on this catalyst is intrinsically dominated by LOM pathway, facilitating the reaction kinetics. This work not only paves an avenue for the rational design of electrocatalysts, but also serves the fundamental insights into the lattice oxygen participation for promising OER application.