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Spinel oxides have emerged as highly active catalysts for the oxygen evolution reaction (OER). However, due to covalency competition, the OER process on spinel oxides often follows an arduous adsorbate evolution mechanism (AEM) pathway. Herein, we propose a novel rare-earth sites substitution strategy to tune the lattice oxygen redox of spinel oxides and bypass the AEM scaling relationship limitation. Taking NiCo2O4 as a model, the incorporation of Ce into the octahedral site induces the formation of Ce-O-M (M: Ni, Co) bridge, which triggers charge redistribution in NiCo2O4. The developed Ce-NiCo2O4 exhibits remarkable OER activity with a low overpotential, satisfactory electrochemical stability, and good practicability in anion-exchange membrane water electrolyzer. Theoretical analyses reveal that OER on Ce-NiCo2O4 surface follows a more favorable lattice oxygen mechanism (LOM) pathway and non-concerted proton-electron transfers compared to pure NiCo2O4, as further verified by pH-dependent behavior and in situ Raman analysis. 18O-labeled electrochemical mass spectrometry directly demonstrates that oxygen originates from the lattice oxygen of Ce-NiCo2O4 during OER. It is discovered that electron delocalization of Ce 4f states triggers charge redistribution in NiCo2O4 through the Ce-O-M bridge, favoring antibonding state occupation of Ni-O bonding in [Ce-O-Ni] site, thereby activating lattice oxygen redox of NiCo2O4 in OER., (© 2024 Wiley‐VCH GmbH.)

Herein, an interfacial electron redistribution is proposed to boost the activity of carbon-supported spinel NiCo 2 O 4 catalyst toward oxygen conversion via Fe, N-doping strategy. Fe-doping into octahedron induces a redistribution of electrons between Co and Ni atoms on NiCo 1.8 Fe 0.2 O 4 @N-carbon. The increased electron density of Co promotes the coordination of water to Co sites and further dissociation. The generation of proton from water improves the overall activity for the oxygen reduction reaction (ORR). The increased electron density of Ni facilitates the generation of oxygen vacancies. The Ni-V O -Fe structure accelerates the deprotonation of *OOH to improve the activity toward oxygen evolution reaction (OER). N-doping modulates the electron density of carbon to form active sites for the adsorption and protonation of oxygen species. Fir wood-derived carbon endows catalyst with an integral structure to enable outstanding electrocatalytic performance. The NiCo 1.8 Fe 0.2 O 4 @N-carbon express high half-wave potential up to 0.86 V in ORR and low overpotential of 270 mV at 10 mA cm -2 in OER. The zinc-air batteries (ZABs) assembled with the as-prepared catalyst achieve long-term cycle stability (over 2000 cycles) with peak power density (180 mWcm -2 ). Fe, N-doping strategy drives the catalysis of biomass-derived carbon-based catalysts to the highest level for the oxygen conversion in ZABs., (© 2024 Wiley‐VCH GmbH.)

As a sustainable valorization route, electrochemical glycerol oxidation reaction (GOR) involves in formation of key OH* and selective adsorption/cleavage of C-C(O) intermediates with multi-step electron transfer, thus suffering from high potential and poor formate selectivity for most non-noble-metal-based electrocatalysts. So, it remains challenging to understand the structure-property relationship as well as construct synergistic sites to realize high-activity and high-selectivity GOR. Herein, we successfully achieve dual-high performance with low potentials and superior formate selectivity for GOR by forming synergistic Lewis and Brønsted acid sites in Ni-alloyed Co-based spinel. The optimized NiCo oxide solid-acid electrocatalyst exhibits low reaction potential (1.219 V@10 mA/cm 2 ) and high formate selectivity (94.0 %) toward GOR. In situ electrochemical impedance spectroscopy and pH-dependence measurements show that the Lewis acid centers could accelerate OH* production, while the Brønsted acid centers are proved to facilitate high-selectivity formation of formate. Theoretical calculations reveal that NiCo alloyed oxide shows appropriate d-band center, thus balancing adsorption/desorption of C-O intermediates. This study provides new insights into rationally designing solid-acid electrocatalysts for biomass electro-upcycling., (© 2024 Wiley‐VCH GmbH.)

The Nickel-based catalysts have a good catalytic effect on the 5-hydroxymethylfurfural electrooxidation reaction (HMFOR), but limited by the conversion potential of Ni 2+ /Ni 3+ , 1.35 V versus RHE, the HMF electrooxidation potential of nickel-based catalysts is generally greater than 1.35 V versus RHE. Considering fluorine has the highest Pauling electronegativity and similar atomic radius of oxygen, the introduction of fluorine into the lattice of metal oxides might promote the adsorption of intermediate species, thus improving the catalytic performance. F is successfully doped into the lattice structure of NiCo 2 O 4 spinel oxide by the strategy of hydrothermal reaction and low-temperature fluorination. As is confirmed by in situ electrochemical impedance spectroscopy and Raman spectroscopy, the introduction of F weakens the interaction force of metal-oxygen covalent bonds of the asymmetric M T -O-M O backbone and improves the valence of Ni in tetrahedra structure, which makes it easier to be oxidized to higher valence active Ni 3+ under the action of electric field and promotes the adsorption of OH - , while the decrease of Co valence enhances the adsorption of HMF with the catalyst. Combining the above reasons, F-NiCo 2 O 4 shows superb electrocatalytic performance with a potential of only 1.297 V versus RHE at a current density of 20 mA cm -2 , which is lower than the most catalyst., (© 2023 Wiley-VCH GmbH.)

The reasonable design and controlled synthesis of efficient and hollow nanocatalysts with plentiful heterointerface and fully exposed active sites to accelerate the electron transfer and mass transfer process for oxygen evolution reaction (OER) is highly desirable for water splitting by electrolysis. Herein, a metal-organic framework (MOF)-engaged strategy is developed to prepare Ce-doped hollow mesoporous NiCo 2 O 4 nanoprisms (NiCo 2 O 4 /CeO 2 HNPs) for enhanced OER. Due to the advanced synthesis strategy generating a large number of interfaces between NiCo 2 O 4 and CeO 2 , as well as modulated electrons of the active center by the synergistic action of multi-metals, the obtained catalyst exhibits excellent OER performance with a small overpotential of 290 mV at current density (J) of 10 mA cm -2 . Spinel/Perovskite hollow nanoprisms synthesized by a similar way demonstrates the versatility of our strategy. This work may provide new insights into the development of rare earth-doped hollow polymetallic spinel oxide catalysts., (© 2023 Wiley-VCH GmbH.)

High catalytic efficiency and long-term stability are two main components for the performance assessment of an electrocatalyst. Previous attention has been paid more to efficiency other than stability. The present work is focused on the study of the stability processed on the FeCoNiRu high-entropy alloy (HEA) in correlation with its catalytic efficiency. This catalyst has demonstrated not only performing the simultaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with high efficiency but also sustaining long-term stability upon HER and OER. The study reveals that the outstanding stability is attributed to the spinel oxide surface layer developed during evolution reactions. The spinel structure preserves the active sites that are inherited from the HEA's intrinsic structure. This work will provide an insightful direction/pathway for the design and manufacturing activities of other metallic electrocatalysts and a benchmark for the assessment of their efficiency-stability relationship., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Magnetic field enhanced electrocatalysis has recently emerged as a promising strategy for the development of a viable and sustainable hydrogen economy via water oxidation. Generally, the effects of magnetic field enhanced electrocatalysis are complex including magnetothermal, magnetohydrodynamic and spin selectivity effects. However, the exploration of magnetic field effect on the structure regulation of electrocatalyst is still unclear whereas is also essential for underpinning the mechanism of magnetic enhancement on the electrocatalytic oxygen evolution reaction (OER) process. Here, it is identified that in a mixed NiFe 2 O 4 (NFO), a large magnetic field can force the Ni 2+ cations to migrate from the octahedral (O h ) sites to tetrahedral (T d ) sites. As a result, the magnetized NFO electrocatalyst (NFO-M) shows a two-fold higher current density than that of the pristine NFO in alkaline electrolytes. The OER enhancement of NFO is also observed at 1 T (NFO@1T) under an operando magnetic field. Our first-principles calculations further confirm the mechanism of magnetic field driven structure regulation and resultant OER enhancement. These findings provide a strategy of manipulating tetrahedral units of spinel oxides by a magnetic field on boosting OER performance., (© 2022 Wiley-VCH GmbH.)

Antioxidant treatment strategy by scavenging reactive oxygen species (ROS) is a highly effective disease treatment option. Nanozymes with multiple antioxidant activities can cope with the diverse ROS environment. However, lack of design strategies and limitation of negative correlation for nanozymes with multiple antioxidant activities hindered their development. To overcome these difficulties, here we used ZnMn 2 O 4 as a model to explore the role of Mn valency at the octahedral site via a valence-engineered strategy, and found that its multiple antioxidant activities are positively correlated with the content of Mn 4+ . Therefore, through this strategy, a self-cascading antioxidant nanozyme LiMn 2 O 4 was constructed, and its efficacy was verified at the cellular level and in an inflammatory bowel disease model. This work not only provides guidance for the design of multiple antioxidant nanozymes, but also broadens the biomedical application potential of multiple antioxidant nanozymes., (© 2022 Wiley-VCH GmbH.)

Atomic substitutions at the tetrahedral site (A Td ) could theoretically achieve an efficient optimization of the charge at the octahedral site (B Oh ) through the A Td -O-B Oh interactions in the spinel oxides (AB 2 O 4 ). Despite substantial progress having been made, the precise control and adjustment of the spinel oxides are still challenging owing to the complexity of their crystal structure. In this work, we demonstrate a simple solvent method to tailor the structures of spinel oxides and use the spinel oxide composites (ACo 2 O 4 /NCNTs, A=Mn, Co, Ni, Cu, Zn) for oxygen electrocatalysis. The optimized MnCo 2 O 4 /NCNTs exhibit high activity and excellent durability for oxygen reduction/evolution reactions. Remarkably, the rechargeable liquid Zn-air battery equipped with a MnCo 2 O 4 /NCNTs cathode affords a specific capacity of 827 mAh g Zn -1 with a high power density of 74.63 mW cm -2 and no voltage degradation after 300 cycles at a high charging-discharging rate (5 mA cm -2 ). The density functional theory (DFT) calculations reveal that the substitution could regulate the ratio of Co 3+ /Co 2+ and thereby lead to the modulation of the electronic structure accompanied with the movement of the d-band center. The tetrahedral and octahedral sites interact through the Mn-O-Co, and the Co 3+ Oh of MnCo 2 O 4 with the optimal charge structure allows a more suitable binding interaction between the active center and the oxygenated species, resulting in superior oxygen electrocatalytic performance., (© 2021 Wiley-VCH GmbH.)

The electrooxidation of 5-hydroxymethylfurfural (HMF) offers a promising green route to attain high-value chemicals from biomass. The HMF electrooxidation reaction (HMFOR) is a complicated process involving the combined adsorption and coupling of organic molecules and OH - on the electrode surface. An in-depth understanding of these adsorption sites and reaction processes on electrocatalysts is fundamentally important. Herein, the adsorption behavior of HMF and OH - , and the role of oxygen vacancy on Co 3 O 4 are initially unraveled. Correspondingly, instead of the competitive adsorption of OH - and HMF on the metal sites, it is observed that the OH - can fill into oxygen vacancy (Vo) prior to couple with organic molecules through lattice oxygen oxidation reaction process, which could accelerate the rate-determining step of the dehydrogenation of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) intermediates. With the modulated adsorption sites, the as-designed Vo-Co 3 O 4 shows excellent activity for HMFOR with the earlier potential of 90 and 120 mV at 10 mA cm -2 in 1 m KOH and 1 m PBS solution. This work sheds insight on the catalytic mechanism of oxygen vacancy, which benefits designing a novel electrocatalysts to modulate the multi-molecules combined adsorption behaviors., (© 2021 Wiley-VCH GmbH.)

Spinel zinc cobalt oxide (ZnCo 2 O 4 ) is not considered as a superior catalyst for the electrochemical oxygen evolution reaction (OER), which is the bottleneck reaction in water-electrolysis. Herein, taking advantage of density functional theory (DFT) calculations, we find that the existence of low-spin (LS) state cobalt cations hinders the OER activity of spinel zinc cobalt oxide, as the t 2g 6 e g 0 configuration gives rise to purely localized electronic structure and exhibits poor binding affinity to the key reaction intermediate. Increasing the spin state of cobalt cations in spinel ZnCo 2 O 4 is found to propagate a spin channel to promote spin-selected charge transport during OER and generate better active sites for intermediates adsorption. The experiments find increasing the calcination temperature a facile approach to engineer high-spin (HS) state cobalt cations in ZnCo 2 O 4 , while not working for Co 3 O 4 . The activity of the best spin-state-engineered ZnCo 2 O 4 outperforms other typical Co-based oxides., (© 2021 Wiley-VCH GmbH.)

The electrosynthesis from 5-hydroxymethylfurfural (HMF) is considered a green strategy to achieve biomass-derived high-value chemicals. As the molecular structure of HMF is relatively complicated, understanding the HMF adsorption/catalysis behavior on electrocatalysts is vital for biomass-based electrosynthesis. The electrocatalysis behavior can be modulated by tuning the adsorption energy of the reactive molecules. In this work, the HMF adsorption behavior on spinel oxide, Co 3 O 4 is discovered. Correspondingly, the adsorption energy of HMF on Co 3 O 4 is successfully tuned by decorating with single-atom Ir. It is observed that compared with bare Co 3 O 4 , single-atom-Ir-loaded Co 3 O 4 (Ir-Co 3 O 4 ) can enhance adsorption with the CC groups of HMF. The synergetic adsorption can enhance the overall conversion of HMF on electrocatalysts. With the modulated HMF adsorption, the as-designed Ir-Co 3 O 4 exhibits a record performance (with an onset potential of 1.15 V RHE ) for the electrosynthesis from HMF., (© 2021 Wiley-VCH GmbH.)

Carbon is usually used as cathode material for Li-O 2 batteries. However, the discharge product, such as Li 2 O 2 and LiO 2 , could react with carbon to form an insulating lithium carbonate layer, resulting in cathode passivation and capacity fading. To solve this problem, the development of non-carbon cathodes is highly desirable. Herein, we successfully synthesized MnCo 2 O 4 (MCO) nanoparticles anchored on porous MoO 2 nanosheets that are grown on Ni foam (current collector) (MCO/MoO 2 @Ni), acting as a carbon- and binder-free cathode for Li-O 2 batteries, in an attempt to improve the electrical conductivity, electrocatalytic activity, and durability. This MCO/MoO 2 @Ni electrode delivers excellent cyclability (more than 400 cycles) and rate performance (voltage gap of 0.75 V at 5000 mA g -1 ). Notably, the battery with this electrode exhibits a high energy efficiency (higher than 85 %). The advanced electrochemical performance of MCO/MoO 2 @Ni can be attributed to its high electrical conductivity, excellent stability, and outstanding electrocatalytic activity. This work offers a new strategy to fabricate high-performance Li-O 2 batteries with non-carbon cathode materials., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)