Reaction Kinetics Research Articles

Monitoring Enzymatic Reaction Kinetics and Activity Assays in Confined Nanospace.

Enzyme-mediating biotransformations commonly occur in micro- and nanospace, which is crucial to maintain the essential biochemical processes and physiological functions in living systems. Probing enzyme-catalytic reactions in a biomimetic fashion remains challenging due to the lack of competent tools and methodology. Here, we show that studying enzymatic reaction kinetics can be readily achieved by a well-designed solid-state nanopore. Using tyrosine as a classical substrate, we quantitatively characterize the catalytic activity of tyrosinase (TYR) and tyrosine decarboxylase (TDC) in a nanoconfined space. Tyrosine was first immobilized in the nanopipette, wherein the active sites of tyrosine were left unoccupied. When successively exposed to TYR and TDC, a two-step cascade reaction can spontaneously take place. In this process, the surface wettability and charge of the nanopipette stemming from the catalytic products can sensitively regulate ion transport and ionic current rectification behavior, which were monitored by ionic current signal. In this biomimetic scenario, we obtained the enzymatic reaction kinetics of monophenyl oxidase that were not previously actualized in the conventional macroenvironment. Significantly, TYR showed higher enzyme activity, with a Km value of 1.59 mM, which was lower than that measured in a free and open space (with a Km of 3.01 mM). This suggests that tyrosine should be the most appropriate substrate of TYR, thus improving our understanding of tyrosine-associated biochemical reactions. This work offers an applicable technical platform to mimic enzyme-mediated biotransformations and biometabolisms.

Enhancing the performance of porous silicon biosensors: the interplay of nanostructure design and microfluidic integration

This work presents the development and design of aptasensor employing porous silicon (PSi) Fabry‒Pérot thin films that are suitable for use as optical transducers for the detection of lactoferrin (LF), which is a protein biomarker secreted at elevated levels during gastrointestinal (GI) inflammatory disorders such as inflammatory bowel disease and chronic pancreatitis. To overcome the primary limitation associated with PSi biosensors—namely, their relatively poor sensitivity due to issues related to complex mass transfer phenomena and reaction kinetics—we employed two strategic approaches: First, we sought to optimize the porous nanostructure with respect to factors including layer thickness, pore diameter, and capture probe density. Second, we leveraged convection properties by integrating the resulting biosensor into a 3D-printed microfluidic system that also had one of two different micromixer architectures (i.e., staggered herringbone micromixers or microimpellers) embedded. We demonstrated that tailoring the PSi aptasensor significantly improved its performance, achieving a limit of detection (LOD) of 50 nM—which is >1 order of magnitude lower than that achieved using previously-developed biosensors of this type. Moreover, integration into microfluidic systems that incorporated passive and active micromixers further enhanced the aptasensor’s sensitivity, achieving an additional reduction in the LOD by yet another order of magnitude. These advancements demonstrate the potential of combining PSi-based optical transducers with microfluidic technology to create sensitive label-free biosensing platforms for the detection of GI inflammatory biomarkers.

Interfacial Engineering of Fluorescent Carbon Dots with Metal Oxides for Real-Time Visualization of Oxygen Vacancy Dynamics.

Oxygen vacancy (Vo), as one of the most common surface defects, significantly influence the physiochemical properties of metal oxides. However, it remains a challenge for existing techniques to visualize the evolution of Vo during redox process due to its heterogeneous distribution, small size, and dynamic nature. Herein, the real-time monitoring of such microscopic interfacial events is reported by advantage of the high-contrast fluorescence response of carbon dots (H-CDs) to Vo. The green emissive H-CDs possess a unique disc-shaped structure and exceptional hydrophilicity, allowing their tight adhesion to the surfaces of Vo-rich MgO by simple mixing. Subsequently, a water involved interfacial reaction occurred between H-CDs and Vo, resulting in gradual quenching of the original green emission and simultaneously emergence of bright red fluorescence. Moreover, the spatiotemporal diffusion dynamics and reaction kinetics are investigated by confocal laser scanning microscopy, revealing the time-dependent reorganization and structural heterogeneity at the interface. The finding provides a new toolbox for in situ imaging of Vo-triggered phenomena at a microscopic level, which will be helpful in promoting the rational design of oxide materials.

Accelerating alcohol oxidation kinetics for electrochemical biomass upgrading via photoinduced active CuIII-O generation

Copper-based compounds exhibit broad prospects in the electrocatalytic oxidation of biomass for sustainable production of high-value-added chemicals due to their passivated oxygen evolution reaction (OER) competitiveness. However, the sluggish reaction kinetics remain the main challenge in constraining their scalable application. Herein, a highly selective electrooxidation of 5-hydroxymethylfurfural (HMF) to 2, 5-furandicarboxylic acid (FDCA) on CuO is achieved via photoinduced surface reconstruction. The experimental results confirmed that the photogenerated hole accumulation on the surface of CuO with matched valence band position can promote the CuOOH active phase generation. Density functional theory (DFT) calculations and the overall relationship between structure and selectivity indicate the CuOOH species can accelerate the spontaneous dehydrogenation process of hydroxyl group. Therefore, the activated CuO electrode under illumination can effectively regulate the conversion of 5-Hydroxymethyl-2-furancarboxylic acid (HMFCA) key intermediates and exhibits accelerated reaction kinetics, FDCA yield increased by 17.79 % compared to dark condition. Additionally, a general enhancement effect on the oxidation of benzyl alcohol and furfuryl alcohol was also revealed. This work introduces photoassistance effect for the first time in HMF oxidation, opening up prospects for the application of photoelectric synergy in biomass value-added conversion and providing insights into the activity mechanism of Cu-based catalysts in organic oxidation.

Stabilized Hf-doped Ti/Sb-SnO2 electrode for efficient degradation of tetracycline.

The electrochemical advanced oxidation process (EAOP) has shown significant promise in the field of refractory organic wastewater treatment due to its high efficiency and environmentally friendly nature. In this study, Ti/Sb-SnO2 electrodes with varying proportions of Hf were prepared using the sol-gel method. The addition of Hf transformed the original collapsing and broken surface into a flat and regular surface. The results demonstrated that Ti/Sb-SnO2-Hf electrode doped with 6% Hf exhibited a higher oxygen evolution potential (OEP) and excellent stability. The OEP increased from 2.315 V without Hf-doping to 2.482 V, and the corresponding actual life was 321.05% higher than that without Hf. The current density (5-40 mA·cm-2), electrolyte concentration (0.02-0.2 mol·L-1), pH (3-11), and initial pollutant concentration (5-80 mg·L-1) were evaluated to confirm the tetracycline (TC) degradation characterization of Ti/Sb-SnO2-6%Hf electrodes. It was concluded that under the optimal degradation conditions, the removal rate of TC could reach 99.66% within 2 h. The degradation of TC follows first-order reaction kinetics. The oxidative degradation of TC was achieved through indirect oxidation, with ·OH playing a dominant role. TC's electrochemical oxidation degradation pathway has been proposed: Based on LC-MS results, three main pathways are speculated. During the electrocatalytic oxidation process, decarboxylation, deamidation, and ring-opening reactions occur under ·OH attack, producing intermediate compounds with m/z values of 427, 433, 350, 246, 461, 424, 330, 352, 309, 263, and 233. These intermediates are further oxidized to intermediate compounds with an m/z value of 218. This work introduces a new efficient anode electrochemical catalyst for the degradation of TC, providing a strategy for industrial applications.

Azatriangulenetrione as the Anode Material for Sodium-Ion Batteries: Reversible Redox Chemistry Mediated by Lone Pair Electrons.

Redox-active organic molecules have potential as electrode materials, but their cycling stability is often limited by the irreversible formation of σ-bonds from the radical intermediates. Herein, we present an effective approach to achieve high reversibility by using lone pair electrons to mediate intramolecular radical-radical coupling. Azatriangulenetrione (1) was examined as the anode in sodium-ion batteries, which displayed a reversible four-step, one-electron redox chemistry. In situ electron spin resonance, ex situ Fourier transform infrared/X-ray photoelectron spectroscopy, and density functional theory calculation revealed that the unstable radical anions can couple with each other through the lone pair electrons of the central nitrogen atom, leading to stabilized radical species. Furthermore, scan-rate-dependent cyclic voltammetry measurements and galvanostatic intermittent titration techniques demonstrated that the redox reaction kinetics for radical formation were much faster than the radical paring process. This study offers deep insights into the design of highly reversible organic electrodes.

Binder-Responsive DNA Strand Displacement Enables High-Throughput and High-Fidelity Discovering of Small Molecular DNA Binders.

High-throughput screening (HTS) is pivotal in the discovery of small molecules that bind to DNA, yet there are limited sensing mechanisms available for designing HTS assays for DNA binders. Herein, we introduce a binder-responsive toehold-mediated DNA strand displacement (BR-TMSD) technique featuring programmable reaction kinetics in response to DNA-binder interactions. When two DNA binders are used, BR-TMSD is initiated through a rapid binder displacement, followed by the DNA strand displacement. The orthogonal displacement reactions of BR-TMSD enables a high-fidelity, dual-channel HTS assay, returning 19 new DNA binders from a library of 1,170 compounds.

High Young's Modulus Li6.4La3Zr1.4Ta0.6O12-Based Solid Electrolyte Interphase Regulating Lithium Deposition for Dendrite-Free Lithium Metal Anode.

Artificial solid electrolyte interphase (SEI) layers have been widely regarded as an effective protection for lithium (Li) metal anodes. In this work, an artificial SEI film consisting of dense Li6.4La3Zr1.4Ta0.6O12 (LLZTO) nanoparticles and polymerized styrene butadiene rubber is designed, which has good mechanical and chemical stability to effectively prevent Li anode corrosion by the electrolyte. The LLZTO-based SEI film can not only guide Li to uniformly deposit at the interface but also accelerate the electrochemical reaction kinetics due to its high Li+ conductivity. In particular, the high Young's modulus of the LLZTO-based SEI will regulate e- distribution in the continuous Li plating/stripping process and achieve uniform deposition of Li. As a consequence, the Li anode with LLZTO-based SEI (Li@LLZTO) enables symmetric cells to demonstrate a stable overpotential of 25 mV for 600 h at a current density of 1 mA cm-2 for 1 mA h cm-2. The Li@LLZTO||LFP (LiFePO4) full cell exhibits a capacity of 106 mA h g-1 after 800 cycles at 5 C with retention as high as 90%. Our strategy here suggests that the artificial SEI with high Young's modulus effectively inhibits the formation of Li dendrites and provides some guidance for the design of higher performance Li metal batteries.

Theoretical study of the second- and third-H-abstraction reactions of monomethylhydrazine and nitrogen dioxide and its application to hypergolic ignition modeling

The chemical kinetics of the second–H-abstraction and the third-H-abstraction reactions of monomethylhydrazine (MMH) and nitrogen dioxide (NO2) and its application to modeling hypergolic ignition of MMH/NO2 were investigated in this work. Potential energy surfaces (PESs) for the key reactions were obtained by employing the CCSD(T)/CBS//M06-2X/6-311++G(d,p) single-reference method and the MRCI(7e,6o)/CBS//M06-2X/6-311++G(d,p) multi-reference method. The RRKM/Master Equation approach was used to calculate the temperature- and pressure-dependent rate constants. For the second-H-abstraction reactions, the trans-CH3NNH and HNO2/HONO are the major products. For the third-H-abstraction reactions, the bimolecular reaction of cis-CH3NNH+NO2→CH3NN+HNO2 is more favorable. The calculated rate constants and thermodynamics data were fitted and incorporated into two existing mechanisms to investigate their influence on modeling MMH/NO2 hypergolic ignition. The modeling results show that the system reactivity of MMH/NO2 is promoted by the second- and third-H-abstraction reactions, as the ignition delay times decrease by a factor of two at 300–800 K. The production rate and sensitivity analyses further validate the significance of the second-H-abstraction reactions at low temperatures. The sensitivity analyses at 1000 K also indicate the necessity of further investigations on CH2O, N2H2/NO2, and CH3NH/NO2 sub-mechanisms for modeling the MMH/NO2 combustion at high temperatures. This work provides not only new kinetic and thermochemical data but also a better understanding of the hypergolic ignition of MMH/NO2.

A neuro‐computational study of viscous dissipation and nonlinear Arrhenius chemical kinetics during the hypodicarbonous acid‐based hybrid nanofluid flow past a Riga plate

A neuro‐computational study of viscous dissipation and nonlinear Arrhenius chemical kinetics during the hypodicarbonous acid‐based hybrid nanofluid flow past a Riga plate

Insights into the catalytic properties of 4,3-α-glucanotransferase to guide the biofabrication of α-glucans with low digestibility.

The effect of the starch chain structure on 4,3-α-glucanotransferase's (4,3-α-GTase) catalytic properties was investigated to modulate the digestibility of starch. Three starches with diverse amylose contents were used, and the enzymatic kinetic reaction of 4,3-α-GTase was fitted using the Michaelis-Menten equation. The results revealed that the linear substrate was more suitable for modification by 4,3-α-GTase. Linear starch chains were then selected with various degrees of polymerization (DP) as substrates of 4,3-α-GTase modification. Additionally, the structures and in vitro digestion of 4,3-α-GTase derived α-glucans were studied. The results showed that enzyme catalysis increased the amount of α-1,3 glycosidic linkages in products (highest 33.5%), the digestibility of 4,3-α-GTase derived α-glucans conformed to a first-order two-phase equation, and the equilibrium digestibility was controlled between 43.2-72.1%. It was observed that the structure of α-glucans could be managed to attain low digestibilities (43.2%) by selecting maltodextrin with DE 2 as the substrate. These findings offer valuable insights into the fabrication of α-glucans and their potential applications in various fields.

Cu-alginate hydrogels in microfluidic systems: a sustainable catalytic approach for click chemistry

This work explores the innovative use of copper-alginate (Cu-alginate) hydrogels within microfluidic systems to catalyze dipolar cycloaddition reactions, emphasizing green chemistry principles and process intensification. Utilizing naturally occurring biopolymers, such as alginates, provides an environmentally friendly alternative to conventional catalyst supports due to their biocompatibility, biodegradability, and effective metal ion immobilization capabilities. The integration of these biopolymer-based catalysts into microfluidic devices allows for precise control over reaction conditions, leading to enhanced reaction kinetics and mass transfer efficiencies. Our results demonstrate that Cu-alginate hydrogels effectively catalyze the formation of 1,4-disubstituted 1,2,3-triazoles through [3 + 2] dipolar cycloaddition reactions with high regioselectivity and conversion. The microfluidic setup ensures rapid and efficient synthesis, surpassing traditional batch reaction methods in both reaction rate and environmental impact by reducing solvent usage and waste generation. Furthermore, the use of microfluidics contributes to the reproducibility and scalability of the synthesis process, important for industrial applications. The model-based design and its simulations have been employed to further understand and optimize the reaction system. Diffusion through the gel layer and catalytic reaction kinetics estimated from experimental data were included in the model, providing a theoretical foundation for a comprehensive process evaluation. This study not only advances the field of sustainable catalysis by demonstrating the practical utility of biopolymer-supported catalysts in microfluidic systems, but also sets the stage for further research into biopolymer applications in complex chemical syntheses.

Enhancing Reversibility and Kinetics of Anionic Redox in O3‐NaLi1/3Mn2/3O2 through Controlled P2 Intergrowth

Anionic redox chemistry can surpass theoretical limits of conventional layered oxide cathodes in energy density. A recent model system of sodium‐ion batteries, O3‐NaLi1/3Mn2/3O2, demonstrated full anionic redox capacity but is limited in reversibility and kinetics due to irreversible structural rearrangement and oxygen loss. Solutions to these issues are missing due to the challenging synthesis. Here, we harness the unique structural richness of sodium layered oxides and realize a controlled ratio of P2 structural intergrowth in this model compound with the overall composition maintained. The resulted O3 with 27% P2 intergrowth structure delivers an excellent initial Coulombic efficiency of 87%, comparable to the state‐of‐the‐art Li‐rich NMCs. This improvement is attributed to the effective suppression of irreversible oxygen release and structural changes, evidenced by operando Differential Electrochemical Mass Spectroscopy and X‐ray Diffraction. The as‐prepared intergrowth material, based on the environmentally benign Mn, exhibits a reversible capacity of 226 mAh g−1 at C/20 rate with excellent cycling stability stemming from the redox reactions of oxygen and manganese. Our work isolates the role of P2 structural intergrowth and thereby introduces a novel strategy to enhance the reversibility and kinetics of anionic redox reactions in sodium layered cathodes without compromising capacity.

Enhancing Reversibility and Kinetics of Anionic Redox in O3-NaLi1/3Mn2/3O2 through Controlled P2 Intergrowth.

Anionic redox chemistry can surpass theoretical limits of conventional layered oxide cathodes in energy density. A recent model system of sodium-ion batteries, O3-NaLi1/3Mn2/3O2, demonstrated full anionic redox capacity but is limited in reversibility and kinetics due to irreversible structural rearrangement and oxygen loss. Solutions to these issues are missing due to the challenging synthesis. Here, we harness the unique structural richness of sodium layered oxides and realize a controlled ratio of P2 structural intergrowth in this model compound with the overall composition maintained. The resulted O3 with 27% P2 intergrowth structure delivers an excellent initial Coulombic efficiency of 87%, comparable to the state-of-the-art Li-rich NMCs. This improvement is attributed to the effective suppression of irreversible oxygen release and structural changes, evidenced by operando Differential Electrochemical Mass Spectroscopy and X-ray Diffraction. The as-prepared intergrowth material, based on the environmentally benign Mn, exhibits a reversible capacity of 226 mAh g-1 at C/20 rate with excellent cycling stability stemming from the redox reactions of oxygen and manganese. Our work isolates the role of P2 structural intergrowth and thereby introduces a novel strategy to enhance the reversibility and kinetics of anionic redox reactions in sodium layered cathodes without compromising capacity.

Carbon Nanofiber-Based Sandwich Free-Standing Cathode for High-Performance Lithium-Sulfur Batteries.

Challenges including rapid capacity degradation and reduced Coulombic efficiency due to the shuttle effect have hindered the commercial viability of lithium-sulfur (Li-S) batteries. A novel sandwich-structured electrode with an optimized electrode structure and current collector interface design was presented as a free-standing positive electrode for Li-S batteries. Fabricated via a simple slurry coating process, the electrode embedded multiwalled carbon nanotubes within carbon nanofiber composite films (PCNF/T). Owing to the superior conductivity and reduced weight in comparison to both carbon nanofibers (PCNF) and the conventional aluminum foil current collector (Al), the PCNF/T electrode exhibited diminished polarization and accelerated redox reaction kinetics. Thus, it delivers an initial discharge capacity of 990.23 mA h g-1 at 0.5 C. Even after 400 cycles, while retains a reversible capacity of 707.45 mA h g-1, corresponding to a minimal capacity degradation rate of merely 0.07% per cycle. Notably, the electrode exhibits a capacity retention of 619.81 mA h g-1 after 400 cycles at 1 C, with a capacity decay rate of only 0.08% per cycle. This study presents an innovative approach to developing a new free-standing cathode for high-performance Li-S batteries.

Anchoring Ni(OH)2-CeOx Heterostructure on FeOOH-Modified Nickel-Mesh for Efficient Alkaline Water-Splitting Performance with Improved Stability under Quasi-Industrial Conditions.

Developing low-cost and industrially viable electrode materials for efficient water-splitting performance and constructing intrinsically active materials with abundant active sites is still challenging. In this study, a self-supported porous network Ni(OH)2-CeOx heterostructure layer on a FeOOH-modified Ni-mesh (NiCe/Fe@NM) electrode is successfully prepared by a facile, scalable two-electrode electrodeposition strategy for overall alkaline water splitting. The optimized NiCe0.05/Fe@NM catalyst reaches a current density of 100 mA cm-2 at an overpotential of 163 and 262mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, in 1.0m KOH with excellent stability. Additionally, NiCe0.05/Fe@NM demonstrates exceptional HER performance in alkaline seawater, requiring only 148mV overpotential at 100mA cm-2. Under real water splitting conditions, NiCe0.05/Fe@NM requires only 1.701V to achieve 100mA cm-2 with robust stability over 1000h in an alkaline medium. The remarkable water-splitting performance and stability of the NiCe0.05/Fe@NM catalyst result from a synergistic combination of factors, including well-optimized surface and electronic structures facilitated by an optimal Ce ratio, rapid reaction kinetics, a superhydrophilic/superaerophobic interface, and enhanced intrinsic catalytic activity. This study presents a simple two-electrode electrodeposition method for the scalable production of self-supported electrocatalysts, paving the way for their practical application in industrial water-splitting processes.

Anchoring Multi‐Coordinated Bismuth Metal Atom Sites on Honeycomb‐Like Carbon Rods Achieving Advanced Potassium Storage

AbstractCarbonaceous materials are recognized for their high conductivity and adaptable structures, making them potential candidates for potassium‐ion batteries (PIBs). Yet, their application has been restricted due to challenges like limited potassium storage and slow kinetics. Addressing these issues, this study presents a novel method by anchoring nitrogen‐oxygen‐coordinated bismuth metal atom sites onto honeycomb‐like carbon rods, termed Bi‐N4‐O2@HCR. This aims to enhance PIB performance by exploiting carbonaceous materials' strengths and mitigating their limitations. Through comprehensive experiments and theoretical simulations, it is found that Bi‐N4‐O2 sites enrich potassium storage and facilitate potassium ion migration, thus improving transport efficiency and reaction kinetics. The resulting anode showcased rapid and durable potassium storage, with a remarkable capacity of 190.7 mAh g−1 at 30 A g−1 and maintaining 192.2 mAh g−1 over 4200 cycles at 5 A g−1, outperforming many existing carbon anodes. Additionally, in full cell tests, it exhibited excellent rate performance and ultra‐long cycle life, sustaining up to 8000 cycles with a stable capacity of 88.9 mAh g−1 at 5 A g−1. This research underscores the significance of incorporating unique metal sites on carbon substrates to advance battery technology.

Molecular-docking electrolytes enable high-voltage lithium battery chemistries.

Ideal rechargeable lithium battery electrolytes should promote the Faradaic reaction near the electrode surface while mitigating undesired side reactions. Yet, conventional electrolytes usually show sluggish kinetics and severe degradation due to their high desolvation energy and poor compatibility. Here we propose an electrolyte design strategy that overcomes the limitations associated with Li salt dissociation in non-coordinating solvents to enable fast, stable Li chemistries. The non-coordinating solvents are activated through favourable hydrogen bond interactions, specifically Fδ--Hδ+ or Hδ+-Oδ-, when blended with fluorinated benzenes or halide alkane compounds. These intermolecular interactions enable a dynamic Li+-solvent coordination process, thereby promoting the fast Li+ reaction kinetics and suppressing electrode side reactions. Utilizing this molecular-docking electrolyte design strategy, we have developed 25 electrolytes that demonstrate high Li plating/stripping Coulombic efficiencies and promising capacity retentions in both full cells and pouch cells. This work supports the use of the molecular-docking solvation mechanism for designing electrolytes with fast Li+ kinetics for high-voltage Li batteries.

Performance of zero-valent iron immobilized on activated carbon cloth for the removal of phenol from wastewater

BackgroundDischarge of large amounts of untreated industrial effluent into water bodies pose significant environmental challenges worldwide. This is due to the limitations of traditional wastewater treatment methods in the treatment of recalcitrant organic pollutants. Fenton processes involves the generation of hydroxyl radicals that are well suited to degrade organics in effluent water. This study focuses on reducing slag generation during Fenton processes and enhancing the reuse of nano-zero-valent iron (NZVI) through the immobilization of NZVI on activated carbon cloth (ACC) through a chitosan (CH) linker with phenol as a model pollutant.ResultsMicrostructural and spectroscopic techniques were employed to study the materials prepared and 37.5 wt% iron loading was achieved. Phenol degradation of 96.3% at 40 °C at pH of 3.0 with 50 mM H2O2 was achieved using ACC-CH-NZVI. Adsorption and degradation studies carried out using ACC-CH-NZVI catalyst revealed that phenol adsorption onto ACC-CH-NZVI fits the Langmuir isotherm model, following the pseudo-second-order kinetic model and first-order reaction kinetics. Thermodynamic studies indicate the non-spontaneous, endothermic and irreversible nature of the removal process. Comparing ACC-CH-NZVI with ACC and ACC-CH, phenol removal using ACC drops from 87.8 to 39%, while using ACC-CH, the removal efficiency drops from 73 to 20.9% and using ACC-CH-NZVI, phenol removal drops from 96.3 to about 70% and total organic carbon removal drops from 79 to about 60% with minimal iron leaching, highlighting the superior performance of ACC-CH-ZVI and the role of NZVI in enhancing phenol removal.ConclusionsThe catalyst demonstrated good stability for phenol degradation to about 70% phenol removal from simulated wastewater and 60% TOC removal from industrial wastewater after five treatment cycles with minimal Fe leaching.Graphical abstract

Elucidating the local structure and electronic properties of a highly active overall alkaline water splitting NixCo1-xO/hollow carbon sphere catalyst

A NixCo1-xO/HCS catalyst with superior water-splitting is presented. High water-splitting reaction kinetics and enhanced durability were observed. The structure-function relationship was investigated with XPS, which demonstrated the presence of dominant Ni2+ and Co2+ species and a functionalized HCS support where nucleation of small metal oxide nanoparticles occurred. The PDF showed broadened Nickel/Cobalt-oxide bonds and expansion of the metal-metal pair distances. The alteration of the Metal-Oxide and Metal-Metal-Oxide bonds favored better HER and OER electrocatalysis, also as supported by DFT. EXAFS showed the existence of the bimetallic oxide catalyst and the stretching of the Ni–O bonds due to the coordination of the Ni–O with the Co. The composite exhibited higher activity and enhanced electrocatalytic mechanism towards water splitting through higher exchange current densities (0.615 and 0.886 mA cm−2) and low charge transfer resistance (14 and 10 Ω) respectively. Chronoamperometry proved the catalyst's stability during prolonged electrolysis.