Optical in situ deciphering of the surface reconstruction-assistant multielectron transfer event of single Co3O4 nanoparticles.

Surface reconstruction determines the fate of catalytic sites on the near-surface during the oxygen evolution reaction. However, deciphering the conversion mechanism of various intermediate-states during surface reconstruction remains a challenge. Herein, we employed an optical imaging technique to draw the landscape of dynamic surface reconstruction on individual Co3O4 nanoparticles. By regulating the surface states of Co3O4 nanoparticles, we explored dynamic growth of the CoOx(OH)y sublayer on single Co3O4 nanoparticles and directly identified the conversion between two dynamics. Rich oxygen vacancies induced more active sites on the surface and prolonged surface reconstruction, which enhanced electrochemical redox and oxygen evolution. These results were further verified by in situ electrochemical extinction spectroscopy of single Co3O4 nanoparticles. We elucidate the heterogeneous evolution of surface reconstruction on individual Co3O4 nanoparticles and present a unique perspective to understand the fate of catalytic species on the nanosurface, which is of enduring significance for investigating the heterogeneity of multielectron-transfer events.

Triggered lattice-oxygen oxidation with active-site generation and self-termination of surface reconstruction during water oxidation.

To master the activation law and mechanism of surface lattice oxygen for the oxygen evolution reaction (OER) is critical for the development of efficient water electrolysis. Herein, we propose a strategy for triggering lattice-oxygen oxidation and enabling non-concerted proton-electron transfers during OER conditions by substituting Al in La0.3Sr0.7CoO3-δ. According to our experimental data and density functional theory calculations, the substitution of Al can have a dual effect of promoting surface reconstruction into active Co oxyhydroxides and activating deprotonation on the reconstructed oxyhydroxide, inducing negatively charged oxygen as an active site. This leads to a significant improvement in the OER activity. Additionally, Al dopants facilitate the preoxidation of active cobalt metal, which introduces great structural flexibility due to elevated O 2p levels. As OER progresses, the accumulation of oxygen vacancies and lattice-oxygen oxidation on the catalyst surface leads to the termination of Al3+ leaching, thereby preventing further reconstruction. We have demonstrated a promising approach to achieving tunable electrochemical reconstruction by optimizing the electronic structure and gained a fundamental understanding of the activation mechanism of surface oxygen sites.

Titanium Self-Intercalation Induced Formation of Orthogonal (1 × 1) Edge/Surface Reconstruction in 1T-TiSe2: Atomic Scale Dynamics and Mechanistic Study.

Edges and surfaces play indispensable roles in affecting the chemical-physical properties of materials, particularly in two-dimensional transition metal dichalcogenides (TMDCs) with reduced dimensionality. Herein, we report a novel edge/surface structure in multilayer 1T-TiSe2, i.e., the orthogonal (1 × 1) reconstruction, induced by the self-intercalation of Ti atoms into interlayer octahedral sites of the host TiSe2 at elevated temperature. Formation dynamics of the reconstructed edge/surface are captured at the atomic level by in situ scanning transmission electron microscopy (STEM) and further validated by density functional theory (DFT), which enables the proposal of the nucleation mechanism and two growth routes (zigzag and armchair). Via STEM-electron energy loss spectroscopy (STEM-EELS), a chemical shift of 0.6 eV in Ti L3,2 is observed in the reconstructed edge/surface, which is attributed to the change of the coordination number and lattice distortion. The present work provides insights to tailor the atomic/electronic structures and properties of 2D TMDC materials.

Nonlinear Electrical Transport Unveils Fermi Surface Malleability in a Moiré Heterostructure.

Van Hove singularities enhance many-body interactions and induce collective states of matter ranging from superconductivity to magnetism. In magic-angle twisted bilayer graphene, van Hove singularities appear at low energies and are malleable with density, leading to a sequence of Lifshitz transitions and resets observable in Hall measurements. However, without a magnetic field, linear transport measurements have limited sensitivity to the band's topology. Here, we utilize nonlinear longitudinal and transverse transport measurements to probe these unique features in twisted bilayer graphene at zero magnetic field. We demonstrate that the nonlinear responses, induced by the Berry curvature dipole and extrinsic scattering processes, intricately map the Fermi surface reconstructions at various fillings. Importantly, our experiments highlight the intrinsic connection of these features with the moiré bands. Beyond corroborating the insights from linear Hall measurements, our findings establish nonlinear transport as a pivotal tool for probing band topology and correlated phenomena.

Reconstruction and Solidification of Dion-Jacobson Perovskite Top and Buried Interfaces for Efficient and Stable Solar Cells.

Quasi-two-dimensional (Q-2D) perovskites show great potential in the field of photonic and optoelectronic device applications. However, defects and local lattice dislocation still limit performance and stability improvement by nonradiative recombination, unpreferred phase distribution, and unbonded amines. Here, a low-temperature synergistic strategy for both reconstructing and solidifying the perovskite top and buried interface is developed. By post-treating the 1,4-phenylenedimethanammonium (PDMA) based (PDMA)MA4Pb5I16 films with cesium acetate (CsAc) before thermal annealing, a condensation reaction between R-COO- and -NH2 and ion exchange between Cs+ and MA+ occur. It converts the unbonded amines to amides and passivates uncoordinated Pb2+. Meanwhile, it adjusts film composition and improves the phase distribution without changing the out-of-plane grain orientation. Consequently, performance of 18.1% and much-enhanced stability (e.g., stability for photo-oxygen increased over 10 times, light-thermal for T90 over 4 times, and reverse bias over 3 times) of (PDMA)MA4Pb5I16 perovskite solar cells are demonstrated.

Engineering the Co(II)/Co(III) Redox Cycle and Coδ+ Species Shuttle for Nitrate-to-Ammonia Conversion.

Electroreduction of waste nitrate to valuable ammonia offers a green solution for environmental restoration and energy storage. However, the electrochemical self-reconstruction of catalysts remains a huge challenge in terms of maintaining their stability, achieving the desired active sites, and managing metal leaching. Herein, we present an electrical pulse-driven Co surface reconstruction-coupled Coδ+ shuttle strategy for the precise in situ regulation of the Co(II)/Co(III) redox cycle on the Co-based working electrode and guiding the dissolution and redeposition of Co-based particles on the counter electrode. As result, the ammonia synthesis performance and stability are significantly promoted while cathodic hydrogen evolution and anodic ammonia oxidation in a membrane-free configuration are effectively blocked. A high rate of ammonia production of 1.4 ± 0.03 mmol cm-2 h-1 is achieved at -0.8 V in a pulsed system, and the corresponding nitrate-to-ammonia Faraday efficiency is 91.7 ± 1.0%. This work holds promise for the regulation of catalyst reactivity and selectivity by engineering in situ controllable structural and chemical transformations.

Surface Facets Reconstruction in Copper-Based Materials for Enhanced Electrochemical CO2 Reduction.

The unavoidable and unpredictable surface reconstruction of metallic copper (Cu) during the electrocatalytic carbon dioxide (CO2) reduction process is a double-edged sword affecting the production of high-value-added hydrocarbon products. It is crucial to control the surface facet reconstruction and regulate the targeted facets/facet interfaces, and further understand the mechanism between activity/selectivity and the reconstructed structure of Cu for CO2 reduction. Based on the current catalyst design methods, a facile strategy combining chemical reduction and electro-reduction is proposed to achieve specified Cu(111) facets and the Cu(110)/(111) interfaces in reconstructed Cu derived from cuprous oxide (Cu2O). The surface facet reconstruction significantly boosted the electrocatalytic conversion of CO2 into multi-carbon (C2+) products comparing to the unmodified catalyst. Theoretical and experimental analyses show that the Cu(110)/(111)s interface between Cu(110) and a small amount of Cu(111) can tailor the reaction routes and lower the reaction energy barrier of C-C coupling to ethylene (C2H4). The work will guide the surface facets reconstruction strategy for Cu-based CO2 electrocatalysts, providing a promising paradigm to understand the structural variation in catalysts.

Reaction with Water Vapor Defines Surface Reconstruction and Membranolytic Activity of Quartz Milled in Different Molecular Environments.

Industrial processing of quartz (SiO2) and quartz-containing materials produces toxic dust. Fracturing quartz crystals opens the Si‒O bond and produces highly reactive surface species which mainly react with molecules like water and oxygen. This surface-reconstruction process forms silanol (Si‒OH) on the quartz surface, which can damage biological membranes under specific configurations. To comprehend the impact of the quartz surface restructuring on membranolytic activity, the formation and reactivity of quartz radicals produced in four distinct molecular environments with electron paramagnetic resonance (EPR) spectroscopy are evaluated and their membranolytic activity is measured through in vitro hemolysis test. The four molecular environments are formulated with and without molecular water vapor and oxygen (±H2O/±O2). The absence of water favored the formation of surface radical species. In water-rich environments, diamagnetic species prevailed due to radical recombination. Quartz milled in -H2O/±O2 acquired membranolytic activity when exposed to water vapor, unlike quartz milled in +H2O/±O2. After being stabilized by reaction with water vapor, the membranolytic activity of quartz is maintained over time. It is demonstrated that the type and the reactivity of radical sites on quartz are modulated by the outer molecular environment, ultimately determining the biological activity of milled quartz dust.

Surface-Reconstructed Ru-Doped Nickel/Iron Oxyhydroxide Arrays for Efficient Oxygen Evolution.

The generation of an active phase through dynamic surface reconstruction is a promising strategy for improving the activity of electrocatalysts. However, studies investigating the reconstruction process and its impact on the intrinsic properties of the catalysts are scarce. Herein, the surface reconstruction of NiFe2 O4 interfaced with NiMoO4 (Ru-NFO/NMO) facilitated by Ru doping is reported. The electrochemical and material characterizations demonstrate that Ru doping can regulate the electronic structure of NFO/NMO and induce the high-valence state of Ni3.6+ δ , facilitating the surface reconstruction to highly active Ru-doped NiFeOOH/NiOOH (SR-Ru-NFO/NMO). The optimized SR-Ru-NFO/NMO exhibits promising performance in the oxygen evolution reaction, displaying a low overpotential of 229 mV at 10 mA cm-2 and good stability at varying current densities for 80 h. Density functional theory calculations indicate that Ru doping can increase the electron density and optimize intermediate adsorption by shifting the d-band center downward. This work provides valuable insights into the tuning of electrocatalysts by surface reconstruction and offers a rational design strategy for the development of highly active oxygen evolution reaction electrocatalysts.

Mo-Induced Surface Reconstruction in Ni/Co-OOH Prickly Flower Clusters for Improving the Hydrogen Production in Alkaline Seawater Splitting.

Seawater electrolysis is the most promising technology for hydrogen production, in which surface reconstruction on the interface of electrode/electrolyte plays a crucial role in activating the catalytic reactions with a low activation energy barrier. Herein, an efficient Mo modifying NiCoMo prickly flower clusters electrocatalyst supported on nickel foam (Mo-doped Ni/Co-OOH prickly flower clusters) is obtained, which serves as an eminently active and durable catalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) due to the surface reconstruction during the alkaline seawater electrolysis with ultralow overpotentials. It just requires a cell voltage of 1.52 V to achieve the current density of 10 mA cm-2 for water electrolysis along with robust durability over 30 h. Mo doping effectively regulates the surface reconstruction of Ni/Co-OOH, which facilitates the adsorption of oxygen-containing intermediates on the active center, and the nonhomogeneous interface induces charge rearrangement for the catalytic process to improve efficiency, providing a new strategy for revealing the seawater electrolytic mechanism.

Modulating Surface Architecture and Electronic Conductivity of Li-rich Manganese-Based Cathode.

Li-rich manganese-based cathode (LRMC) has attracted intense attention to developing advanced lithium-ion batteries with high energy density. However, LRMC is still plagued by poor cyclic stability, undesired rate capacity, and irreversible oxygen release. To address these issues, herein, a feasible polyvinylidene fluoride (PVDF)-assisted interface modification strategy is proposed for modulating the surface architecture and electronic conductivity of LRMC by intruding the F-doped carbon coating, spinel structure, and oxygen vacancy on the LRMC, which can greatly enhance the cyclic stability and rate capacity, and restrain the oxygen release for LRMC. As a result, the modified material delivers satisfactory cyclic performance with a capacity retention of 90.22% after 200 cycles at 1 C, an enhanced rate capacity of 153.58 mAh g-1 at 5 C and 126.32 mAh g-1 at 10 C, and an elevated initial Coulombic efficiency of 85.63%. Moreover, the thermal stability, electronic conductivity, and structure stability of LRMC are also significantly improved by the PVDF-assisted interface modification strategy. Therefore, the strategy of simultaneously modulating the surface architecture and the electronic conductivity of LRMC provides a valuable idea to improve the comprehensive electrochemical performance of LRMC, which offers a promising reference for designing LRMC with high electrochemical performance.

Surface Reconstruction Regulation of Co3N Through Heterostructure Engineering Toward Efficient Oxygen Evolution Reaction.

Oxygen evolution reaction (OER) electrocatalysts generally experience structural and electronic modifications during electrocatalysis. This phenomenon, referred to as surface reconstruction, results in the formation of catalytically active species that act as real OER sites. Controlling surface reconstruction therefore is vital for enhancing the OER performance of electrocatalysts. In this study, a new approach is introduced of heterostructure engineering to facilitate the surface reconstruction of target catalysts. Using MnCo carbonate hydroxide (MnCo─CH)@Co3N as a demonstration, it is discovered that the surface reconstruction occurs more readily and rapidly on MnCo─CH@Co3N than on Co3N. More interestingly, during the reconstruction process, Mn species migrate to the surface, enabling the in situ formation of highly active Mn-doped CoOOH. Consequently, the MnCo─CH@Co3N catalyst after reconstruction exhibits a low overpotential of 257 mV at 10 mA cm-2, compared to 379 mV of individual Co3N. This work offers fresh perspectives on understanding the enhanced OER performance of heterostructure electrocatalysts and the role of heterostructure in promoting surface reconstruction.

Promoting Oxygen Evolution Electrocatalysis by Coordination Engineering in Cobalt Phosphate.

Understanding the structure-activity correlation is an important prerequisite for the rational design of high-efficiency electrocatalysts at the atomic level. However, the effect of coordination environment on electrocatalytic oxygen evolution reaction (OER) remains enigmatic. In this work, the regulation of proton transfer involved in water oxidation by coordination engineering based on Co3(PO4)2 and CoHPO4 is reported. The HPO4 2- anion has intermediate pKa value between Co(II)-H2O and Co(III)-H2O to be served as an appealing proton-coupled electron transfer (PCET) induction group. From theoretical calculations, the pH-dependent OER properties, deuterium kinetic isotope effects, operando electrochemical impedance spectroscopy (EIS) and Raman studies, the CoHPO4 catalyst beneficially reduces the energy barrier of proton hopping and modulates the formation energy of high-valent Co species, thereby enhancing OER activity. This work demonstrates a promising strategy that involves tuning the local coordination environment to optimize PCET steps and electrocatalytic activities for electrochemical applications. In addition, the designed system offers a motif to understand the structure-efficiency relationship from those amino-acid residue with proton buffer ability in natural photosynthesis.

The Reconstruction of Pt(001) Surface and the Shell-Like Reconstruction of the Vicinal Pt(001) Surfaces Revealed by Neural Network Potential.

In this work, a highly accurate neural network potential (NNP) is presented, named PtNNP, and the exploration of the reconstruction of the Pt(001) surface and its vicinal surfaces with it. Contrary to the most accepted understanding of the Pt(001) surface reconstruction, the study reveals that the main driving force behind Pt(001) quasi-hexagonal reconstruction is not the surface stress relaxation but the increased coordination number of the surface atoms resulting in stronger intralayer binding in the reconstructed surface layer. In agreement with experimental observations, the optimized supercell size of the reconstructed Pt(001) surface contains (5 × 20) unit cells. Surprisingly, the reconstruction of the vicinal Pt(001) surfaces leads to a smooth shell-like surface layer covering the whole surface and diminishing sharp step edges.

Rb-Doped Perovskite Oxides: Surface Enrichment and Structural Reconstruction During the Oxygen Evolution Reaction.

Alkali-metal doped perovskite oxides have emerged as promising materials due to their unique properties and broad applications in various fields, including photovoltaics and catalysis. Understanding the complex interplay between alkali metal doping, structural modifications, and their impact on performance remains a crucial challenge. In this study, this challenge is addressed by investigating the synthesis and properties of Rb-doped perovskite oxides. These results reveal that the doping of Rb into perovskite oxides function as a structural modifier in the as-synthesized samples and during the oxygen evolution reaction (OER) as well. Electron microscopy and first-principles calculations confirm the enrichment of Rb on the surface of the as-synthesized sample. Further investigations into the electrocatalytic reaction revealed that the Rb-doped perovskite underwent drastic restructuring with Rb leaching and formation of strontium oxide.

Dissolution-Induced Surface Reconstruction of Ni0.95Pt0.05Si/p-Si Photocathode for Efficient Photoelectrochemical H2 Production.

Metal silicide/Si photoelectrodes have demonstrated significant potential for application in photoelectrochemical (PEC) water splitting to produce H2. To achieve an efficient and economical hydrogen evolution reaction (HER), a paramount consideration lies in attaining exceptional catalytic activity on the metal silicide surface with minimal use of noble metals. Here, this study presents the design and construction of a novel Ni0.95Pt0.05Si/p-Si photocathode. Dopant segregation is used to achieve a Schottky barrier height as high as 1.0 eV and a high photovoltage of 420 mV. To achieve superior electrocatalytic activity for HER, a dissolution-induced surface reconstruction (SR) strategy is proposed to in situ convert surface Ni0.95Pt0.05Si to highly active Pt2Si. The resulting SR Ni0.95Pt0.05Si/p-Si photocathode exhibits excellent HER performance with an onset potential of 0.45 V (vs RHE) and a high maximum photocurrent density of 40.5 mA cm-2 and a remarkable applied bias photon-to-current efficiency (ABPE) of 5.3% under simulated AM 1.5 (100 mW cm-2) illumination. The anti-corrosion silicide layer effectively protects Si, ensuring excellent stability of the SR Ni0.95Pt0.05Si/p-Si photoelectrode. This study highlights the potential for achieving efficient PEC HER using bimetallic silicide/Si photocathodes with reduced Pt consumption, offering an auspicious perspective for the cost-effective conversion of solar energy to chemical energy.

Heterostructure Engineering of NiCo-LDHs for Enhanced Energy Storage Performance in Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are considered a promising device for next-generation energy storage due to their high safety and low cost. However, developing high-performance cathodes that can be matched with zinc metal anodes remains a challenge in unlocking the full potential of AZIBs. In this study, a typical transition metal layered double hydroxides (NiCo-LDHs) can be in situ reconstructed to NiCo-LDHs/Ni(Co)OOH heterostructure using an electrochemical cycling activation (ECA) method, serving as a novel cathode material for AZIBs. The optimized ECA-NiCo-LDHs cathode demonstrates a high capacity of 181.5 mAh g-1 at 1 A g-1 and retains 75% of initial capacity after 700 cycles at 5 A g-1. The abundant heterointerfaces of the NiCo-LDHs/Ni(Co)OOH material can activate additional active sites for zinc-ion storage and accelerate ion diffusion. Theoretical calculations also suggest the heterostructure can boost charge transfer and regulate ion-adsorption capability, thereby improving the electrochemical performance. Additionally, the flexible AZIBs device exhibits good service performance. This study on interface engineering introduces a new possibility for utilizing LDHs in AZIBs and offers a novel strategy for designing electrode materials.

In Situ Raman Study of Surface Reconstruction of FeOOH/Ni3S2 Oxygen Evolution Reaction Electrocatalysts.

Construction of heterojunctions is an effective strategy to enhanced electrocatalytic oxygen evolution reaction (OER), but the structural evolution of the active phases and synergistic mechanism still lack in-depth understanding. Here, an FeOOH/Ni3S2 heterostructure supported on nickel foam (NF) through a two-step hydrothermal-chemical etching method is reported. In situ Raman spectroscopy study of the surface reconstruction behaviors of FeOOH/Ni3S2/NF indicates that Ni3S2 can be rapidly converted to NiOOH, accompanied by the phase transition from α-FeOOH to ß-FeOOH during the OER process. Importantly, a deep analysis of Ni─O bond reveals that the phase transition of FeOOH can regulate the lattice disorder of NiOOH for improved catalytic activity. Density functional theory (DFT) calculations further confirm that NiOOH/FeOOH heterostructure possess strengthened adsorption for O-containing intermediates, as well as lower energy barrier toward the OER. As a result, FeOOH/Ni3S2/NF exhibits promising OER activity and stability in alkaline conditions, requiring an overpotential of 268 mV @ 100 mA cm-2 and long-term stability over 200 h at a current density of 200 mA cm-2. This work provides a new perspective for understanding the synergistic mechanism of heterogeneous electrocatalysts during the OER process.

Interaction of C60 with Methylammonium Lead Iodide Perovskite Surfaces: Unveiling the Role of C60 in Surface Engineering.

Understanding the interaction between fullerene (C60) and perovskite surfaces is pivotal for advancing the efficiency and stability of perovskite solar cells. In this study, we investigate the adsorption behavior of C60 on methylammonium lead iodide (MAPbI3) surfaces using periodic density functional theory calculations. We explore various surface terminations and defect configurations to elucidate the influence of surface morphology on the C60-perovskite interaction, computing the adsorption energy and transfer of charge. Our results reveal distinct adsorption energies and charge transfer mechanisms for different surface terminations, shedding light on the role of surface defects in modifying the electronic structure and stability of perovskite materials. Furthermore, we provide insights into the potential of C60 to passivate surface defects, playing a relevant role in the surface reconstruction after the formation of defects. This comprehensive understanding of C60-perovskite interactions offers valuable guidelines about the role of fullerenes on surface structure and reconstruction.

Construction of living-cell tissue engineered amniotic membrane for ocular surface disease.

BACKGROUND: Human amniotic membrane (AM) transplantation has been applied to treat ocular surface diseases, including corneal trauma. The focus of much deliberation is to balance the mechanical strength of the amniotic membrane, its resistance to biodegradation, and its therapeutic efficacy. It is commonly observed that the crosslinked human decellularized amniotic membranes lose the functional human amniotic epithelial cells (hAECs), which play a key role in curing the injured tissues. METHODS AND RESULTS: In this study, we crosslinked human decellularized amniotic membranes (dAM) with genipin and re-planted the hAECs onto the genipin crosslinked AM. The properties of the AM were evaluated based on optical clarity, biodegradation, cytotoxicity, and ultrastructure. The crosslinked AM maintained its transparency. The color of crosslinked AM deepened with increasing concentrations of genipin. And the extracts from low concentrations of genipin crosslinked AM had no toxic effect on human corneal epithelial cells (HCECs), while high concentrations of genipin exhibited cytotoxicity. The microscopic observation and H&E staining revealed that 2 mg/mL genipin-crosslinked dAM (2 mg/mL cl-dAM) was more favorable for the attachment, migration, and proliferation of hAECs. Moreover, the results of the CCK-8 assay and the transwell assay further indicated that the living hAECs' tissue-engineered amniotic membranes could facilitate the proliferation and migration of human corneal stromal cells (HCSCs) in vitro. CONCLUSIONS: In conclusion, the cl-dAM with living hAECs demonstrates superior biostability and holds significant promise as a material for ocular surface tissue repair in clinical applications.