Oxidation Research Articles

Dynamic modulation of electron redistribution at the heterogeneous interface nickel hydroxides/platinum boosts acidic oxygen reduction reaction

The interfacial electron interactions in heterogeneous catalysts are critical in determining the adsorption strengths and configurations of reaction intermediates, which are essential for the efficiency of multistep tandem catalytic processes. Amorphous-crystalline (a-c) heterostructures have garnered significant interest due to their unusual atomic arrangements, adaptable electron configurations, and exceptional stability. Here, we introduce a mesoporous a-c heterojunction catalyst featuring enriched amorphous-crystalline Ni(OH)2/Pt boundaries (ac-Ni(OH)2@m-Pt), designed for efficient acidic oxygen reduction reaction (ORR). This catalyst enables electron redistribution at the heterogeneous interface, thereby enhancing both catalytic activity and durability. As anticipated, the ac-Ni(OH)2@m-Pt delivers a high mass activity (MA) of 0.95 A mgPt−1 and maintains good durability (89.8% MA retention) over 15000 cycles. Advanced characterization and theoretical calculations reveal that the catalyst’s high performance stems from the dynamic heterogeneous-interface electron redistribution at the a-c interface. This dynamic-cycling electron transfer, driven by the applied potential, promotes O2 activation and accelerates the protonation of *O intermediate during ORR. This work offers a promising avenue for improving the design of electrocatalysts using a-c interface engineering.

Ion-Docking Effect Enabling Rechargeable High-Voltage Magnesium-Iodine/Chlorine Battery.

Rechargeable magnesium (Mg) batteries represent a promising energy storage system by offering low cost and dendrite-less propensity. However, the limited selection of cathode materials, and often with low voltage and capacity, constrain Mg batteries. Herein, by exploiting the ion-docking effect between two halogen species - iodine cations (I+) and chlorine anions (Cl-) - we activate the cathodic activity of halogens and develop a magnesium-iodine/chlorine (Mg-I/Cl) battery prototype with high energy and power density. The ion-docking effect enables I+ and Cl- to mutually balance and disperse their charges, weakens the coordination strength between Cl- and Mg2+ while enhances the stability of I+, thus facilitating the multi-electron (2+1/3) redox reactions of halogens. We also find the solvation state of iodine species determine the reaction process of the I0/I3-/I- redox couples. The here-developed magnesium-iodine/chlorine battery features an impressively high discharge plateau of up to 3.0 V with a high capacity exceeding 400 mAh g-1, and demonstrates a stable lifespan for 500 cycles, with the ability of ultra-fast charging at 20C and low-temperature cycling under -30 °C. These findings may provide new insights for developing high-energy-density Mg battery systems.

Efficient Oxygen Reduction Catalysis on Fe4 Cluster Site Facilitated by Adjacent Single Atom.

The inherent sluggish kinetics of the conventional four-electron transfer pathway fundamentally limits the oxygen reduction reaction (ORR) efficiency. While electronic structure modulation offers potential solutions, developing effective catalytic regulation strategies remains challenging due to elusive structure-activity correlations. In this study, Fe4 cluster sites are engineered with dual parallel electron transfer channels that enable concurrent O─O bond cleavage and dual oxygen atom protonation. This unique configuration facilitates an optimized two-step double electron transfer mechanism, significantly enhancing ORR kinetics. Synergistic Mn single atom sites, strategically positioned as electron reservoirs, substantially elevate the electron density of Fe4 clusters while reinforcing Fe─N coordination bonds through charge redistribution. Remarkably, the spatial configuration of Fe4 clusters at the support periphery minimizes steric confinement effects, allowing simultaneous product desorption and oxygen adsorption - a critical advantage for sustaining continuous catalytic cycles. Through combined experimental and theoretical analyses, it is demonstrated that this dual-channel electron transport system effectively reduces activation barriers for elementary steps while accelerating charge transfer kinetics. This fundamental study establishes a new paradigm for designing high-performance ORR catalysts through multi-site collaborative engineering and reaction pathway optimization.

Harnessing Bio-Inspired Axial Coordination to Boost Synergistic Effects for Enhanced Bifunctional Oxygen Electrocatalysis.

Strategic alteration of the chelating atoms around the metal center can modify the electronic band structure of the electrocatalyst, improving its performance in oxygen evolution and reduction reactions (OER/ORR). Advancements in the development of catalysts with heteroatoms and axial modifications in the coordination sphere are mostly limited to single-molecule electrocatalysts or elevated temperature-mediated pyrolysis approaches for oxygen electrocatalysis. Inspired by biological catalytic systems with axial coordination, a pyrolysis-free strategic methodology is adopted for the synthesis of an iron-metaled covalent organic polymer matrix axially laminated over cobalt-based metal-organic framework through an imidazole moiety. Precise engineering of coordination atoms in synthesized core-shell material, featuring dual metal sites with distinct neighboring atom exhibits mutual synergy due to the presence of bridging imidazole moiety between two metal sites. Modulated synergism navigates the electronic structure such that it favors specific reactant adsorption on specific metal sites during bifunctional O2 electrocatalysis as confirmed through in situ Raman spectroscopy and in situ attenuated total reflection infrared (ATR-IR) spectroscopy. Through dynamic correlation between the in-situ studies and modified d-band center obtained theoretically, the pivotal role of axial coordination linkage mediated synergism favoring ORR/OER process via target-specific reactant adsorption is demonstrated.

Suppression of ATP-dependent (S)-NAD(P)H-hydrate dehydratase expression inhibits adipocyte differentiation of 3T3-L1 preadipocytes by increasing excessive accumulation of NADHX.

ATP-dependent (S)-NAD(P)H-hydrate dehydratase (NAXD) is a crucial enzyme in the nicotinamide adenine dinucleotide repair system that regenerates NAD(P)H, an essential electron donor in metabolic redox reactions. NAD+-related metabolic pathways connect cellular metabolism and the expression of genes responsible for adipogenesis; however, the biological significance of the NAXD-mediated repair pathway remains unclear. Herein, we showed that NAXD is essential for normal adipocyte differentiation of 3T3-L1 murine preadipocytes. Silencing of the Naxd gene attenuated differentiation-induced lipid accumulation with excessive accumulation of hydrated NADH (NADHX) without altering NAD+ levels. FK866, a specific inhibitor of NAMPT, further reduced lipid accumulation even in Naxd-silenced cells with substantial decrease in NAD+. Supplementation with nicotinamide mononucleotide, a precursor of NAD+, restored NAD+ levels comparably in Naxd- and LacZ-silenced cells treated with FK866, but failed to recover adipocyte differentiation of Naxd-silenced cells to the level of LacZ-silenced cells. In contrast, exposure of wild-type 3T3-L1 cells to NADHX recapitulated the Naxd deficiency-elicited inhibitory effects on adipocyte differentiation with reduced expression of master transcriptional regulators of adipogenesis, peroxisome proliferator-activated receptor γ and CCAAT/enhancer binding protein α. These results suggest that NAXD supports normal adipogenesis, in part, by inhibiting excessive accumulation of NADHX.

CNT-Supported RuNi Composites Enable High Round-Trip Efficiency in Regenerative Fuel Cells.

Regenerative fuel cells hold significant potential for efficient, large-scale energy storage by reversibly converting electrical energy into hydrogen and vice versa, making them essential for leveraging intermittent renewable energy sources. However, their practical implementation is hindered by the unsatisfactory efficiency. Addressing this challenge requires the development of cost-effective electrocatalysts. In this study, a carbon nanotube (CNT)-supported RuNi composite with low Ru loading is developed as an efficient and stable catalyst for alkaline hydrogen and oxygen electrocatalysis, including hydrogen evolution, oxygen evolution, hydrogen oxidation, and oxygen reduction reaction. Furthermore, a regenerative fuel cell using this catalyst composite is assembled and evaluated under practical relevant conditions. As anticipated, the system exhibits outstanding performance in both the electrolyzer and fuel cell modes. Specifically, it achieves a low cell voltage of 1.64V to achieve a current density of 1 A cm- 2 for the electrolyzer mode and delivers a high output voltage of 0.52V at the same current density in fuel cell mode, resulting in a round-trip efficiency (RTE) of 31.6% without further optimization. The multifunctionality, high activity, and impressive RTE resulted by using the RuNi catalyst composites underscore its potential as a single catalyst for regenerative fuel cells.

Recent advances in de novo designed metallopeptides as tailored enzyme mimics.

Recent advances in de novo designed metallopeptides as tailored enzyme mimics.

Cryptic iron cycling influenced by organic carbon availability in a seasonally stratified lake.

Iron cycling including phototrophic Fe(II) oxidation has been observed in multiple permanently stratified meromictic lakes, yet less focus has been on dimictic lakes which seasonally overturn and are vastly more common. Here we investigated iron cycling in a dimictic lake, Großes Heiliges Meer in northwest Germany, using 16S rRNA amplicon sequencing, as well as in-situ and lab-based experiments. Bacterial community composition in the lake follows geochemical gradients and differs markedly between oxic and anoxic conditions. Potential iron-metabolizing bacteria were found mostly in anoxic conditions at 7 and 8 m depth and were comprised of taxa from the genera Chlorobium, Thiodictyon, Sideroxydans, Geobacter and Rhodoferrax. We were able to recreate active iron cycling 1) with an ex-situ microbial community from 8 m depth and 2) with a successful microbial enrichment culture from 7 m depth. Varying the light and organic carbon availability in lab-based experiments showed that Fe(III) reduction overshadows Fe(II) oxidation leading to a cryptic iron cycle. Overall we could demonstrate that microbial iron cycling can be a key biogeochemical process in dimictic lakes despite regular disturbance, and that complex environmental factors like organic substrates control the balance between Fe(II) oxidation and Fe(III) reduction.

Regulating Electron Distribution in Regioisomeric Covalent Organic Frameworks for Efficient Solar-Driven Hydrogen Peroxide Production.

Covalent organic frameworks (COFs) are emerging as a transformative platform for photocatalytic hydrogen peroxide (H2O2) production due to their highly ordered structures, intrinsic porosity, and molecular tunability. Despite their potential, the inefficient utilization of photogenerated charge carriers in COFs significantly restrains their photocatalytic efficiency. This study presents two regioisomeric COFs, α-TT-TDAN COF and β-TT-TDAN COF, both incorporating thieno[3,2-b]thiophene moieties, to investigate the influence of regioisomerism on the excited electron distribution and its impact on photocatalytic performance. The β-TT-TDAN COF demonstrates a remarkable solar-to-chemical conversion efficiency of 1.35%, outperforming its α-isomeric counterpart, which is merely 0.44%. Comprehensive spectroscopic and computational investigations reveal the critical role of subtle substitution change in COFs on their electronic properties. This structural adjustment intricately connects molecular structure to charge dynamics, enabling precise regulation of electron distribution, efficient charge separation and transport, and localization of excited electrons at active sites. Moreover, this finely tuned interplay significantly enhances the efficiency of the oxygen reduction reaction. These findings establish a new paradigm in COF design, offering a molecular-level strategy to advance COFs and reticular materials toward highly efficient solar-to-chemical energy conversion.

MOF-Derived Ni5P4 Nanoparticles Based on the Microemulsion Strategy for Supercapacitors and Water Splitting.

With the rapid advancement of energy storage and conversion systems (ESCSs), renewable energy can achieve a smooth and continuous output capacity. Nevertheless, commercial precious metal-based multifunctional ESCSs materials are plagued by issues like scarcity and high production costs. This study adopted microemulsion and chemical vapor deposition (CVD) strategies to fabricate single crystal Ni5P4 nanoparticles successfully. Due to its excellent crystal integrity and high electrical conductivity, single crystal Ni5P4 offers abundant active sites for redox reactions. Additionally, it allows electrons and ions to move more efficiently and freely, making it a highly promising multifunctional material for ESCSs. For supercapacitors (SCs), the prepared Ni5P4-10 electrode possesses a battery-like behavior with a high specific capacity of 1643.13 F g-1@0.5 A g-1. The corresponding assembled Ni5P4-10//AC hybrid SCs (HSCs) exhibit a maximum energy density of 37.78 Wh kg-1 at a power density of 400 W kg-1. Furthermore, Ni5P4-10 displays low overpotentials of 150 mV@HER and 250 mV@OER at 10 mA cm-2 when it serves as an electrocatalyst. This study offers a novel perspective for the design of MOF-derived multifunctional ESCSs materials.

Atomic Layer Thickness Modulated the Catalytic Activity of Platinum for Oxygen Reduction and Hydrogen Oxidation Reaction.

Reducing platinum (Pt) usage and enhancing its catalytic performance in the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) are vital for advancing fuel cell technology. This study presents the design and investigation of monolayer and few-layer Pt structures with high platinum utilization, developed through theoretical calculations. By minimizing the metal thickness from 1 to 3 atomic layers, an atomic utilization rate ranging from 66.66% to 100% is achieved, in contrast to conventional multilayer Pt structures. This reduction resulted in a unique surface coordination environment. These thinner structures exhibited nonlinear fluctuations in key electronic characteristics-such as the d-band center, surface charge, and work function-as the atomic layer thickness decreased. These variations significantly impacted species adsorption and the Pt-H2O interfacial structure, which in turn affected the catalytic activity. Notably, 1-layer Pt exhibited the best performance for HOR, while 3-layer Pt showed high activity for both HOR and ORR. The findings establish a clear relationship between atomic layer thickness, surface characteristics, adsorption behavior, electric double-layer structure, and catalytic performance in Pt systems. This research contributes to a deeper understanding of precision atomic-structured electrocatalyst design and paves the way for the development of highly effective, low-loading Pt-based catalytic materials.

Engineering Proton-Coupled Electron Transfer to Break Activity-Stability Trade-off of Oxygen Electroreduction Catalysts for Temperature-Adaptive Zn-Air Battery.

Single-atom catalysts (SACs) are regarded as effective electrocatalysts for oxygen reduction reaction (ORR). However, integrating high active and long-term durability on SACs is still challenging due to the severe limitations of activity-stability trade-off. Herein, we report an integrative electrocatalyst combining isolated Fe sites and MoC nanoparticles (MoC/Fe-NC). MoC nanoparticles accelerate ORR kinetics via the proton-feeding effect and optimize Fe site microstructure. Thus, MoC/Fe-NC exhibits a high alkaline ORR activity with half-wave potential (E1/2) of 0.916 V vs. the reversible hydrogen electrode, and exceptional durability of 50k cycles with 5 mV E1/2 loss. The observed ORR performance is further verified in a zinc-air battery (ZAB) with a high peak power density of 316 mW cm-2 and operational stability over 1000 h. Moreover, the fabricated temperature-adaptive quasi-solid-state ZAB can cycle stably for 150 h under alternating temperatures. Theory calculations and experiment characterizations, involving scanning electrochemical microscopy techniques and distribution of relaxation times analysis, reveal that the excellent capabilities of MoC/Fe-NC arise from accelerated proton-coupled electron transfer, weakened *OH adsorption, and strengthened Fe-N bonds fueled by MoC nanoparticles. This work sheds light on breaking the activity-stability trade-off barrier of SACs for energy-conversion applications.

Uncovering the Nonmonotonic Relationship between Total Activity and Single-Atom Density for Oxygen Reduction Catalysis.

In common sense, the total activity of single-atom catalysts (SACs) increases monotonically with the densification of single-atom sites, encouraging a general effort in developing high-density SACs for a variety of reactions, such as the oxygen reduction reaction (ORR). However, the intrinsic activity of each single-atom site may not remain constant with increasing density, since their growing interactions at the subnanometer scale can no longer be ignored. Here we report the nonmonotonic relationship between ORR activity and single-atom density, as revealed by theoretical calculations and experimental validation. Taking cobalt-embedded carbon as the model SAC for ORR, when the distance between neighboring Co sites is reduced below about 0.5 nm, proximity effects including hydrogen bonding and steric hindrance between adjacent intermediates dominate the ORR energetics, leading to a unexpected drop in the intrinsic activity. Our experiments unambiguously verified that both the total and mass activities of Co-SACs show turning points with increasing single-atom density. This counterintuitive nonmonotonic relationship between total activity and single-atom density may guide the rational design of high-performance SACs with optimal site densities.

A High-Rate and Ultrastable Ammonium Ion-Air Battery Enabled by the Synergy of ORR and NH4 + Storage.

Ammonium ion batteries (AIBs) offer cost-effectiveness, nontoxicity, and eco-friendly attributes in energy storage technology. However, the constrained capacity and poor stability of conventional cathode materials have impeded their widespread adoption. Herein, a synergistic approach is introduced to overcome these challenges, by enhancing the air cathode with NH4 + and simultaneously leveraging atmospheric oxygen as a reservoir for NH4 + storage. Notably, NH4 + significantly enhances the oxygen reduction reaction (ORR) performance in neutral environments. Through in situ Raman spectroscopy and quantum density functional theory calculations, it is elucidated how NH4 + can act as a proton donor, replacing H2O in neutral media and reducing energy barriers in the protonation of *O2 - and *O, thereby accelerating ORR kinetics. The resulting ammonium ion-air battery, comprising an air cathode and a polymer (PNP) anode, showcases impressive metrics: high energy density of 78 Wh kg-1 and power density of 9369 W kg-1 at 1 A g-1, an initial capacity of 94.3 mAh g-1 and exceptional cycling stability (70.4% capacity retention after 12500 cycles) at 10 A g-1. This pioneering research highlights the synergistic relationship between ORR and NH4 + storage and opens up new avenues for the design and advancement of innovative, sustainable, and environment-friendly AIBs.

Robust Redox-Active Tetrathiafulvalene-Cobalt Metal-Organic Frameworks for Supercapatteries with Promoting Electrochemical Performances.

Integrating abundant electroactive sites and redox reactions into stable metal-organic framework (MOF) electrodes is an effective and relatively unexplored approach to improve the performance of emerging supercapatteries. In this study, electroactive Co(II) was chosen to coordinate with a redox-active tetrathiafulvalene (TTF) ligand to construct a new MOF, formulated as [Co(TTF(py)4)(BDC)] (1) (TTF(py)4 is tetra(4-pyridyl)-TTF and H2BDC is terephthalic acid). Crystallographic characterization indicated that 1 possesses a three-dimensional 6-fold interpenetrating diamond-like topology with high crystal density. Isostructural [Zn(TTF(py)4)(BDC)] (2) was also synthesized to explore the effect of metal ions on the performance of supercapatteries. When directly used as an electrode material in a 3-electrode system, the iodine-treated MOFs 1 and 2 (namely 1-ox and 2-ox, respectively) electrodes exhibit battery-type performance and high capacities. The specific capacities are 1072.2 and 857.8 C g-1 at 1 A g-1 for 1-ox and 2-ox, respectively. The AC||1-ox supercapattery device presents a specific energy of 100.8 Wh kg-1 at a specific power of 0.975 kW kg-1. Ex situ characterizations and theoretical calculations revealed that the excellent performance of 1-ox originates from the synergistic effect of the robust topology, Co(II) metal centers, and ligand dominant mechanism.

A high-performance nitrogen-rich ZIF8-derived $$\textrm{Fe}-\textrm{Co}-\textrm{NC}$$ electrocatalyst for the oxygen reduction reaction

A high-performance nitrogen-rich ZIF8-derived $$\textrm{Fe}-\textrm{Co}-\textrm{NC}$$ electrocatalyst for the oxygen reduction reaction

Ni Single Atoms/Nanoparticles-Decided Spatial Adjustment of Photocatalytic Redox Sites Boosting CO2 Reduction in H2O Vapour.

The kinetics matching of CO2reduction and H2O oxidation is required in sacrificial agent-free photocatalytic CO2reduction. It indicates that the modification engineering on photocatalytic H2O oxidation half-reaction except that on photocatalytic CO2reduction half-reaction should be equally paid attention, which has been easily ignored in most of the literatures. Herein, Ni single atoms (NiSAs) and nanoparticles (NiNPs) co-loaded Ti-MOF-derived TiO2having a flower-like nanospheremicrostructure (NiSAs@NPs/TC) was developed for synchronous design of well-defined redox active sites of photocatalytic CO2 reduction and H2O oxidation. It was verified that NiNPs and NiSAs as the active sites of CO2 reduction and H2O oxidation, respectively, synergically accelerated photocatalytic redox reactions and enhanced separation of photo-generated carriers. NiSAs@NPs/TC showed a remarkable photocatalytic CO2-reduction performance (CO and CH4 products: 35.60 and 3.41 μmol g-1 h-1, respectively) in H2O vapour which was at the advanced level in published relevant studies. Furthermore, the reaction process of CO2 reduction on NiNPs was proposed based on the key intermediates capture of CO and CH4 production in photocatalytic CO2 reduction by in situ analysis.

Multiphasic condensates formed with mono-component of tetrapeptides via phase separation

Biomolecular condensates, formed by liquid-liquid phase separation of biomacromolecules, play crucial roles in regulating physiological events in biological systems. While multiphasic condensates have been extensively studied, those derived from a single component of short peptides have not yet been reported. Here, we report the symmetrical core-shell structural biomolecular condensates formed with a programmable tetrapeptide library via phase separation. Our findings reveal that tryptophan is essential for core-shell structure formation due to its strongest homotypical π-π interaction, enabling us to modulate the structure of condensates from core-shell to homogeneous by altering the amino acid composition. Molecular dynamics simulation combined with cryogenic focused ion beam scanning electron microscopy and cryogenic electron microscopy show that the inner core of multiphasic tetrapeptide condensates is solid-like, consisting of ordered structures. The core is enveloped by a liquid-like shell, stabilizing the core structure. Furthermore, we demonstrate control over multiphasic condensate formation through intrinsic redox reactions or post-translational modifications, facilitating the rational design of synthetic multiphasic condensates for various applications on demand.

A TiO2-modified porous carbon fiber interlayer for long-term cycling and high-rate lithium-sulfur batteries.

Lithium-sulfur batteries (LSBs) are increasingly viewed as promising alternatives to traditional lithium-ion batteries. However, their practical application is hindered by challenges such as polysulfide shuttling and the slow kinetics of sulfur redox reactions. Herein, we have developed an interlayer composed of titanium dioxide nanoparticle-modified porous carbon fibers (TiO2-PCF), created through the carbonization of facial tissue. The high polarity and excellent electrolyte wettability of TiO2-PCF significantly enhance the electrochemical performance of the sulfur cathode. Notably, it achieves a high initial capacity of 1492 mA h g-1 at 0.1C, demonstrates a minimal decay rate of 0.11% over 200 cycles at 0.5C, and maintains a high capacity of 554 mA h g-1 at 2C. This study presents an effective approach to markedly enhance the performance of the sulfur cathode, providing essential insights for future advancements in LSBs.

Yeast-Derived Phosphorus for Eco-friendly Synthesis of Cu3P/Biochar Catalysts with Enhanced Hydrogen Peroxide-based Fenton-like Reaction.

Yeast-Derived Phosphorus for Eco-friendly Synthesis of Cu3P/Biochar Catalysts with Enhanced Hydrogen Peroxide-based Fenton-like Reaction.