Key Takeaways & Executive Findings
- •• • Glycine-intercalated NiFe-LDH achieves an overpotential of 240 mV at 10 mA cm−2 in 1.0 M KOH, a 40 mV improvement over pristine NiFe-LDH (280 mV), directly lowering the energy input required for hydrogen production. • • The Tafel slope is reduced to 38 mV dec−1 from 52 mV dec−1, indicating faster reaction kinetics and more favorable charge transfer, which is critical for high-current-density industrial electrolyzers. • • The electrochemically active surface area increases by 2.3-fold, and charge transfer resistance drops from 12.5 Ω to 4.8 Ω, enhancing catalytic site accessibility and electron transport, thereby improving overall electrode efficiency. • • Long-term stability is demonstrated with 95% activity retention after 24 h of continuous operation at 10 mA cm−2, addressing durability concerns for practical water splitting applications.
Abstract
The sluggish kinetics of the oxygen evolution reaction (OER) remains a bottleneck for efficient water splitting. NiFe-layered double hydroxides (LDHs) are promising OER catalysts, but their performance is often limited by the high-spin state of Fe3+ and poor structural stability. Here, we report a series of amino acid-intercalated iron-rich NiFe-LDHs (AA-NiFe-LDHs) synthesized via a facile one-step coprecipitation method. Intercalation of glycine, alanine, and valine into the interlayer galleries expands the interlayer spacing and induces a partial transition of Fe3+ from high-spin to low-spin state, as confirmed by X-ray absorption spectroscopy and Mössbauer spectroscopy. The low-spin Fe3+ enhances the intrinsic catalytic activity by optimizing the adsorption energy of oxygen intermediates. Among the series, the glycine-intercalated sample (Gly-NiFe-LDH) exhibits the best OER performance in 1.0 M KOH, with an overpotential of 240 mV at 10 mA cm−2 and a Tafel slope of 38 mV dec−1, significantly outperforming the pristine NiFe-LDH (280 mV, 52 mV dec−1). Moreover, Gly-NiFe-LDH shows excellent long-term stability, retaining 95% of its initial activity after 24 h of chronopotentiometry at 10 mA cm−2. The intercalation also increases the electrochemically active surface area by 2.3-fold and reduces the charge transfer resistance from 12.5 Ω to 4.8 Ω. This work demonstrates that amino acid intercalation is an effective strategy to modulate the spin state of Fe3+ and enhance the OER performance of NiFe-LDHs, providing a new avenue for designing high-efficiency, low-cost electrocatalysts.
1. Introduction
Electrochemical water splitting is a cornerstone of green hydrogen production, yet its efficiency is severely hampered by the oxygen evolution reaction (OER) at the anode. The OER involves a four-electron transfer process with sluggish kinetics, requiring high overpotentials to drive the reaction at meaningful rates. Precious metal oxides such as IrO2 and RuO2 are the benchmark catalysts, but their high cost and scarcity limit large-scale deployment. Transition metal-based catalysts, particularly NiFe-layered double hydroxides (LDHs), have emerged as promising alternatives due to their low cost, high activity, and tunable composition. However, the intrinsic activity of NiFe-LDHs is often constrained by the electronic structure of Fe3+, which typically resides in a high-spin state, leading to suboptimal adsorption energies for reaction intermediates.
To overcome this bottleneck, researchers have explored various strategies including defect engineering, heteroatom doping, and interlayer anion modification. Among these, intercalation of organic molecules into the LDH interlayer galleries offers a unique opportunity to modulate the local coordination environment and electronic configuration of metal centers. In this work, we introduce amino acids as intercalants to induce a spin-state transition of Fe3+ from high-spin to low-spin, thereby enhancing the intrinsic OER activity. This approach not only improves catalytic performance but also provides a simple, scalable synthesis route, addressing the critical need for cost-effective and durable OER catalysts for industrial water electrolysis.
Loading authentic research manuscript (Pages 1–5)...
CHEN Tingting, ZHANG Jiaqi, YIN Taishan, TAN Zhicheng, CHEN Long, PANG Huan, HUANG Zhongjie (2026). Amino Acid Intercalated Iron-Rich NiFe-LDHs with Low-Spin Fe3+ for Oxygen Evolution Reaction Electrocatalysis. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4239-2
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the specific mechanism by which amino acid intercalation induces the low-spin state of Fe3+ and how does this affect the OER activity?
Amino acid intercalation expands the interlayer spacing and alters the ligand field around Fe3+ ions, promoting a transition from high-spin to low-spin configuration. This is confirmed by XAS and Mössbauer spectroscopy. The low-spin Fe3+ optimizes the d-band center, leading to more favorable adsorption energies for OER intermediates, thereby reducing the overpotential by 40 mV compared to pristine NiFe-LDH.
How does the intercalation affect the electrochemical surface area and charge transfer resistance, and what are the implications for high-rate operation?
Intercalation increases the electrochemically active surface area by 2.3-fold, providing more accessible active sites. Additionally, the charge transfer resistance decreases from 12.5 Ω to 4.8 Ω, facilitating faster electron transfer. These improvements are critical for maintaining low overpotentials at high current densities, which is essential for industrial electrolyzers operating at 200-500 mA cm−2.
What is the long-term stability of the glycine-intercalated NiFe-LDH under continuous operation, and what degradation mechanisms are observed?
The catalyst retains 95% of its initial activity after 24 h of chronopotentiometry at 10 mA cm−2, indicating excellent stability. Post-analysis suggests minimal structural changes, with no significant Fe leaching or phase transformation, likely due to the stabilizing effect of the intercalated amino acids.
How does the performance of the amino acid-intercalated NiFe-LDH compare to state-of-the-art OER catalysts, and what is the cost advantage?
The overpotential of 240 mV at 10 mA cm−2 is competitive with many noble metal-based catalysts (e.g., IrO2 ~300 mV) and other non-noble metal catalysts. The synthesis uses inexpensive iron and nickel salts and amino acids, making it significantly cheaper than IrO2 or RuO2, with potential for scalable production.
What is the role of the specific amino acid (glycine vs. alanine vs. valine) in determining the catalytic performance, and is there an optimal chain length or functional group?
Glycine, the smallest amino acid, provides the highest interlayer expansion and most effective spin-state transition, leading to the best OER performance. Larger amino acids like alanine and valine also improve activity but to a lesser extent, likely due to steric hindrance and less efficient interaction with the metal centers. This suggests that smaller intercalants with simple structures are more effective.
Related Chinese Research & Cross-Citations
Ammonium Vanadate Cathodes in Aqueous Zinc-Ion Batteries: Design Strategies and Research Progress
Aqueous zinc-ion batteries (AZIBs) offer a compelling combination of high safety, environmental compatibility, and abundant zinc resources, positioning them as viable candidates for grid-scale energy storage. Their practical deployment, however, is constrained by cathode materials that suffer from structural degradation, sluggish Zn2+ diffusion, and inadequate electronic conductivity. Ammonium vanadates (AVOs) have emerged as high-performance cathodes owing to their layered or tunneled frameworks, which accommodate reversible Zn2+ (de)intercalation with diffusion coefficients superior to conventional vanadium oxides. This review systematically examines recent advances in AVO cathodes for AZIBs, correlating morphological variations—including nanowires, nanobelts, and microflowers—with electrochemical characteristics. The analysis establishes structure–performance relationships that govern capacity retention, rate capability, and cycling stability. Key optimization strategies are critically assessed: defect engineering to enhance electronic conductivity and active site density, interlayer spacing modulation via pre-intercalated cations or structural water to facilitate Zn2+ transport, and composite construction with conductive carbonaceous or polymeric matrices to mitigate dissolution and improve mechanical integrity. Despite these advances, challenges persist in achieving long-term cycling stability (>10,000 cycles) and high areal mass loading (>10 mg cm-2) required for commercial viability. The review concludes by outlining future research directions, including operando characterization of degradation mechanisms and scalable synthesis routes for AVO cathodes in practical AZIB configurations.
Microenvironment-responsive therapeutic platforms: Innovations for spinal cord injury repair
Spinal cord injury (SCI) remains a formidable clinical challenge due to the complex, dynamic lesion microenvironment that impedes axonal regeneration and functional recovery. This highlight examines a microenvironment-responsive therapeutic platform integrating microneedle delivery, ferroptosis modulation, and hydrogen therapy. The platform leverages the pathological hallmarks of SCI—oxidative stress, iron dyshomeostasis, and lipid peroxidation—to achieve spatiotemporally controlled cargo release. By combining microneedle arrays for minimally invasive intraparenchymal administration with hydrogen-releasing biomaterials, the system addresses the dual bottlenecks of poor drug penetration across the blood-spinal cord barrier and insufficient neutralization of reactive oxygen species. Ferroptosis inhibition is achieved through iron chelation and glutathione peroxidase 4 (GPX4) stabilization, while hydrogen gas scavenges hydroxyl radicals and peroxynitrite. This multimodal strategy attenuates secondary injury cascades, reduces glial scar formation, and promotes neural stem cell differentiation. The work is supported by the National Natural Science Foundation of China (82574518) and the Talent Cultivation Project of Paring Academicians with Young Talents in higher education institutions in Zhejiang. The authors declare no conflict of interest. This highlight underscores the translational potential of microenvironment-responsive platforms for SCI repair, emphasizing the need for rigorous preclinical validation and scalable manufacturing.
Dual-Site Adsorption over Phosphorus-Doped Copper Oxide for Efficient CO2 Electroreduction to Ethylene
Electroreduction of CO2 to ethylene offers a promising route for renewable electricity storage, yet achieving high ethylene selectivity at industrial current densities remains challenging due to the large energy barrier for C–C coupling. Here, we report a “MOF-assisted in situ doping” strategy to introduce the oxophilic nonmetal phosphorus (P) into the copper oxide (CuO) lattice, constructing a localized Cu–P dual-site adsorption configuration for the key *OCCHO intermediate. The optimized catalyst delivers an impressive Faradaic efficiency of 64.6% for ethylene with a partial current density of 646 mA cm-2. Comprehensive structural characterizations demonstrate that P mainly occupies Cu sites, generating abundant lattice defects and oxygen vacancies. In situ synchrotron infrared spectroscopy and theoretical calculations reveal that P doping modulates the electronic structure of Cu, optimizes the binding energies of *CO and *CHO, and stabilizes *OCCHO via P–O/Cu–C dual-site adsorption, thereby significantly lowering the asymmetric C-C coupling energy barrier to 0.74 eV. This work highlights a dual-site microenvironment regulation strategy for CO2-to-ethylene electroreduction.
Hydrophilic Single-Atom Interface Unlocks Low-Potential CO Removal on Pt in PEMFCs
Proton exchange membrane fuel cells (PEMFCs) fed with reformate hydrogen suffer severe anode poisoning by trace CO, necessitating high CO electrooxidation potentials that degrade performance and durability. This work introduces a Pt@CrSA-N-C anode catalyst featuring a hydrophilic Cr single-atom interface that simultaneously weakens CO adsorption on Pt via electronic regulation and promotes water activation, thereby lowering the CO oxidation onset potential to approximately 0.13 V vs. RHE. The onset potential was determined by two independent methods: the first potential at which the background-corrected current exceeds 0 mA cm-2 during CO oxidation reaction tests in a three-electrode system, and the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. The catalyst achieves a maximum power density under 100 ppm CO that surpasses reported advanced catalysts, as compiled in Table S5. Structural, spectroscopic, and electrochemical characterizations collectively establish a coherent rationale for the hydrophilic single-atom interface strategy. This approach addresses the longstanding trade-off between CO tolerance and Pt utilization, offering a viable route for low-potential CO removal in practical PEMFC anodes.
An Ionoelastomer-Based Bioinspired Wearable Electronics with Tele-Perception and Tactile Sensation for Machine Learning-Assisted Rehabilitation Management
Comprehensive assessment of rehabilitation efficiency is essential for designing appropriate training programs for better musculoskeletal functional recovery. Existing contact-receptor-dependent rehabilitation assessment systems mostly focus on assessing the restoration of muscle function by evaluating grip strength or joint flexion angle; however, parameters reflecting neuromuscular synergistic function are always overlooked. Herein, we develop an ionoelastomer-based soft artificial electroreceptor (SAER) that integrates tele-perception and tactile sensation to track the rehabilitation process, collecting signals related to approaching speed and grip strength sequentially. The SAER uses polyurethane ionoelastomer incorporated with quasi-solid conductive salt as the electric field receptor, and is integrated on a rehabilitation-training ball after assembly to establish an untethered detection device; this enables the remote capture of hand approaching parameter within a 9 cm range, followed by the quantification of grip strength when contacting and grasping. Furthermore, a data-driven assessment system is established by integrating machine learning, which accurately classifies rehabilitation efficiency into six levels; it supports for rehabilitation evaluation and training programs adjustment. Overall, the SAER-based rehabilitation management system establishes a paradigm that synergistically evaluating parameters corresponding to neuromuscular functional restoration and holds strong potential for home-based active rehabilitation for minimizing dependence on frequent clinical supervision.
Microwave-Absorbing Materials with Strong Environmental Adaptability for Corrosion Protection, Anti-Icing, and Thermal Management
Microwave-absorbing materials (MAMs) deployed on naval vessels, aerospace vehicles, and critical electronic systems face coupled electromagnetic, marine salt-spray corrosion, and extreme-temperature loads that legacy single-function absorbers cannot withstand. This review consolidates progress on three environmentally adaptive MAM classes: corrosion-protective, anti-icing, and thermal-management absorbers. The electromagnetic loss and impedance-matching fundamentals are first established, then the synergistic mechanisms, design strategies, and characterization protocols for each class are examined against representative material systems and their measured performance. The analysis identifies a shared design logic—multiscale hierarchical architecture, interfacial polarization engineering, and multifunctional phase integration—while distinguishing the divergent protection mechanisms: barrier and passivation effects for corrosion, surface-energy and latent-heat regulation for anti-icing, and phonon–electron transport decoupling for thermal management. Persistent bottlenecks include the trade-off between impedance matching and protective-layer density, the absence of standardized coupled-field test protocols, and the scarcity of long-term salt-spray and thermal-cycling durability data. Future directions are delineated: intelligent self-adaptive absorbers, multiphysics-coupled simulation frameworks, and environmentally benign multifunctional integration. The review provides a theoretical and technical basis for the design, construction, and engineering scale-up of next-generation high-performance absorbers for aerospace, electronic, and marine equipment.