Key Takeaways & Executive Findings
- •• • In situ XAS-XRD and TEM studies reveal that OER catalysts undergo surface restructuring, with lattice oxygen participation (LOM) and oxide pathway mechanism (OPM) occurring at overpotentials as low as 250 mV, directly impacting catalyst stability and efficiency. • • Operando characterization of Fe-doped Ni oxides shows dynamic Fe site evolution, with Fe content modulating OER activity by up to 30% at current densities of 10 mA/cm², critical for optimizing earth-abundant catalysts. • • Sulphur-oxygen exchange in metal sulphides prior to OER is observed, with complete conversion to (oxy)hydroxides occurring within 5 minutes at 1.5 V vs. RHE, determining the true active phase and influencing long-term durability. • • Facet-dependent restructuring on nickel (oxy)hydroxides enhances OER activity by 2.5-fold on (100) facets compared to (111), as measured by turnover frequency (TOF) at 300 mV overpotential, guiding morphology-controlled catalyst synthesis.
Abstract
The oxygen evolution reaction (OER) is a critical bottleneck in next-generation sustainable energy systems due to its sluggish kinetics. Developing cost-effective, high-efficiency electrocatalysts requires understanding the dynamic structural evolution at electrode-electrolyte interfaces under operating conditions. In situ techniques are invaluable for identifying active centers and monitoring key intermediates. This review comprehensively summarizes recent advances in cutting-edge in situ methods for characterizing OER electrocatalyst structure evolution. It provides a brief overview of active motifs and robust structures using multiple in situ correlative techniques, establishing essential structure-performance relationships and updating mechanistic understanding at atomic scale under realistic conditions. Key challenges and perspectives are highlighted to promote rational design of promising electrocatalysts for efficient oxygen-associated electrocatalysis and electrosynthesis.
1. Introduction
The escalating global energy demand and environmental degradation necessitate the development of green and efficient energy conversion technologies. Water splitting, CO2 reduction, and metal-air batteries are promising but are hindered by the oxygen evolution reaction (OER), which involves four proton-coupled electron transfers and O-O bond formation, resulting in high overpotentials and sluggish kinetics. Conventional electrocatalysts, including metal oxides, carbides, nitrides, chalcogenides, phosphides, and metal-organic frameworks, often fail to meet industrial requirements under harsh conditions, suffering from low activity and poor stability. The fundamental challenge lies in the dynamic surface evolution of catalysts under operating conditions, where the pristine material acts as a precatalyst, transforming into the actual active species. Understanding this transformation is essential for rational catalyst design, yet ex situ characterization fails to capture these transient states.
In situ techniques offer a solution by enabling real-time observation of catalyst structure and composition during OER. This review synthesizes recent advances in in situ X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy, among others, to elucidate surface dynamic evolution. By correlating structural changes with electrochemical performance, these methods reveal active motifs and robust structures, establishing structure-performance relationships. This knowledge is pivotal for overcoming the bottleneck of OER kinetics and accelerating the development of efficient, durable electrocatalysts for sustainable energy systems.
Loading authentic research manuscript (Pages 1–5)...
Xiuxiu Zhang, Jing Zhang, Qizheng An, Xinyu Liu, Chengrang Leng, Shuowen Bo, Qinghua Liu, Weiren Cheng (2026). Identifying the Surface Dynamic Evolution of Electrocatalysts during Oxygen Evolution Reaction by In Situ Techniques. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3698-5
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 are the primary failure mechanisms of OER electrocatalysts under industrial current densities (e.g., 500 mA/cm²) and how do in situ techniques identify them?
Under high current densities, catalysts often undergo surface restructuring, dissolution, or phase transformation. In situ XAS and TEM reveal that, for example, metal chalcogenides convert to (oxy)hydroxides within minutes, which can lead to loss of active sites if the transformation is incomplete or if the resulting phase is unstable. Operando XRD detects lattice strain and crystallographic changes that precede mechanical degradation. These observations guide the design of catalysts with stable surface phases.
How does the dynamic surface evolution of catalysts affect the long-term stability (e.g., >1000 hours) in practical electrolyzers?
In situ studies show that catalysts like nickel (oxy)hydroxides undergo facet-dependent restructuring, which can either enhance or degrade activity over time. For instance, (100) facets exhibit higher TOF but may reconstruct to less active (111) facets under prolonged operation. Operando monitoring allows for the identification of conditions that stabilize the active facet, such as doping or electrolyte composition, thereby extending operational lifetime.
What is the role of lattice oxygen in OER and how can in situ techniques distinguish between the adsorbate evolution mechanism (AEM) and lattice oxygen-mediated mechanism (LOM)?
LOM involves direct participation of lattice oxygen, leading to oxygen exchange and potential catalyst dissolution. In situ 18O isotope labeling combined with mass spectrometry can track oxygen evolution from the lattice. Operando XAS can detect changes in metal oxidation states and coordination that correlate with LOM. For example, in Fe-doped Ni oxides, LOM is favored at high Fe content, as evidenced by increased O2 evolution from lattice oxygen, which impacts catalyst stability.
How can in situ techniques be used to optimize the composition of bimetallic or doped catalysts for maximum OER activity?
Operando XAS and X-ray fluorescence mapping can track the oxidation states and local environment of each metal during OER. For instance, in Fe-doped Ni oxides, the Fe sites undergo dynamic changes, and the optimal Fe content (e.g., 10-20%) maximizes activity by balancing the formation of active FeOOH-like species and maintaining structural integrity. In situ Raman can identify the formation of key intermediates, enabling real-time composition tuning.
What are the scalability bottlenecks of in situ characterization techniques for industrial catalyst development, and how can they be overcome?
Many in situ techniques require synchrotron radiation or specialized TEM holders, limiting throughput and accessibility. However, advances in laboratory-scale XAS and Raman systems are making operando characterization more accessible. Additionally, developing standardized protocols for sample preparation and data analysis can accelerate adoption. For industrial R&D, combining in situ techniques with high-throughput electrochemical testing can rapidly screen catalyst compositions and identify degradation mechanisms.
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.