Induced Surface Reconstruction Research Articles

High-Performance Thermally Evaporated Blue Perovskite Light-Emitting Diodes Enabled by Post-Evaporation Passivation

Thermally evaporated perovskite light-emitting diodes (PeLEDs) are promising for next-generation displays, yet process-compatible passivation strategies for performance enhancement are still lacking. Herein, an effective in-situ surface passivation strategy using post-evaporated metformin hydrochloride (MFCl) is introduced in co-evaporated PeLEDs. MFCl post-deposited onto the perovskite film induces surface reconstruction, improving surface uniformity and healing grain boundaries. Additionally, MFCl penetrates deeply into the perovskite film, passivating both undercoordinated Pb and halide ions at grain boundaries. By employing this strategy, we achieve thermally evaporated blue PeLEDs with a peak external quantum efficiency (EQE) of 9.2 % and a maximum luminance of 1820 cd/m−2(−|-), emitting at a peak wavelength of 488 nm. Furthermore, this strategy effectively suppresses ion migration, significantly enhancing the spectral stability and device lifetime of the blue PeLEDs. This work provides a process-compatible defect passivation strategy for thermally evaporated PeLEDs, laying the foundation for further advancements in this field.

Ultrasonic-assisted Fenton reaction inducing surface reconstruction endows nickel/iron-layered double hydroxide with efficient water and organics electrooxidation

Nickel/iron-layered double hydroxide (NiFe-LDH) tends to undergo an electrochemically induced surface reconstruction during the water oxidation in alkaline, which will consume excess electric energy to overcome the reconstruction thermodynamic barrier. In the present work, a novel ultrasonic wave-assisted Fenton reaction strategy is employed to synthesize the surface reconstructed NiFe-LDH nanosheets cultivated directly on Ni foam (NiFe-LDH/NF-W). Morphological and structural characterizations reveal that the low-spin states of Ni2+ (t2g6eg2) and Fe2+ (t2g4eg2) on the NiFe-LDH surface partially transform into high-spin states of Ni3+ (t2g6eg1) and Fe3+ (t2g3eg2) and formation of the highly active species of NiFeOOH. A lower surface reconstruction thermodynamic barrier advantages the electrochemical process and enables the NiFe-LDH/NF-W electrode to exhibit superior electrocatalytic water oxidation activity, which delivers 10 mA cm−2 merely needing an overpotential of 235 mV. Besides, surface reconstruction endows NiFe-LDH/NF-W with outstanding electrooxidation activities for organic molecules of methanol, ethanol, glycerol, ethylene glycol, glucose, and urea. Ultrasonic-assisted Fenton reaction inducing surface reconstruction strategy will further advance the utilization of NiFe-LDH catalyst in water and organics electrooxidation.

Extensive photochemical restructuring of molecule-metal surfaces under room light

The molecule-metal interface is of paramount importance for many devices and processes, and directly involved in photocatalysis, molecular electronics, nanophotonics, and molecular (bio-)sensing. Here the photostability of this interface is shown to be sensitive even to room light levels for specific molecules and metals. Optical spectroscopy is used to track photoinduced migration of gold atoms when functionalised with different thiolated molecules that form uniform monolayers on Au. Nucleation and growth of characteristic surface metal nanostructures is observed from the light-driven adatoms. By watching the spectral shifts of optical modes from nanoparticles used to precoat these surfaces, we identify processes involved in the photo-migration mechanism and the chemical groups that facilitate it. This photosensitivity of the molecule-metal interface highlights the significance of optically induced surface reconstruction. In some catalytic contexts this can enhance activity, especially utilising atomically dispersed gold. Conversely, in electronic device applications such reconstructions introduce problematic aging effects.

Critical role of post-treatment induced surface reconstruction for high performance inorganic tin-lead perovskite solar cells

Inorganic CsPb0.7Sn0.3I3 perovskites with low-bandgap (1.2 to 1.4 eV) are desired absorber materials for solar cells owing to their ideal bandgap and compositional stability. However, the performances of inorganic Pb-Sn perovskite solar cells are much lower than their Pb-based and hybrid Pb-Sn (e.g. CsPbX3 and FAMAPbSnX3) PSCs, which might be ascribed to its poor film-forming morphology and easy oxidation of Sn2+ at the surface. Here, for the first time, a combined 1-(4-fluorophenyl) piperazine (1-4FP) additive and 1-4FP post-treatment strategy was adopted to obtain high-quality pinhole-free films through a significant surface reconstruction. Specifically, the interaction introduced by 1-4FP post-treatment can effectively prevent the inevitable Sn2+ oxidation on perovskite surface, resulting from crosslinking neighboring perovskite grains with hydrogen bonds of amine group binding to the perovskite surface. As a result, the device treated by this combined strategy achieved a PCE of 17.19 %, which is the highest efficiency of Pb-Sn alloyed inorganic PSCs (sub-1.4 eV) reported to date. In addition, the unsealed 1-4FP-treated devices maintained their initial efficiencies of approximately 100 % after storage in a nitrogen atmosphere for 4000 h. Our findings open a new avenue to obtain high-quality inorganic Pb-Sn perovskite films and associated solar cells.

In situ growth of surface-reconstructed aluminum fluoride nanoparticles on N, F codoped hierarchical porous carbon nanofibers as efficient ORR/OER bifunctional electrocatalysts for rechargeable zinc-air batteries

Modified porous carbon fibers have emerged as crucial electrocatalytic materials for zinc-air battery (ZAB) systems. However, most methods for preparing porous carbon fibers are complex and exhibit single functionality and poor catalytic activity, which hinders the development of ZABs. In this study, we design and synthesize a novel type of N, F codoped hierarchical porous carbon fiber with in situ growth of aluminum fluoride nanoparticles (AlF3@HPCNFs) through electrospinning and high-temperature carbonization. The N, F codoping effectively adjusts the charge density of neighboring carbon atoms and introduces additional active sites. Furthermore, the catalytic process induces surface reconstruction of AlF3 nanoparticles, allowing for their full exposure to the liquid electrolyte and accelerated catalytic reactions. Additionally, this interconnected hierarchical porous structure accelerates mass transfer at the oxygen/carbon-based substrate/electrolyte three-phase interfaces, thereby enhancing reaction kinetics and the accessibility of catalytic active sites, ultimately improving the utilization efficiency of these sites. Consequently, the AlF3@HPCNFs catalyst exhibits excellent bifunctional performance with a narrow potential difference (△E = 0.67 V). Moreover, the obtained bifunctional electrocatalyst is utilized for rechargeable ZABs, surpassing commercially available Pt/C + RuO2 cells in terms of high specific capacity (796 mAh gzn−1) and outstanding cycling stability (over 500 h). This research demonstrates the potential of AlF3@HPCNFs as a bifunctional electrocatalyst and introduces a simplified and effective method for the fabrication of metal fluoride-modified and hierarchically porous carbon nanofibers for rechargeable ZABs.

Gas induced surface reconstruction of CuZnSi catalyst for methanol synthesis

Reconstruction of heterogeneous catalyst is essential for understanding the structure-performance relationship, however, it still remains limitations of the methodology development. Herein we reveal a gas induced activation strategy to reconstruct the surface of CuZnOx/mSi catalyst through pretreating it in various environments, including CO, H2, and H2&CO mixture. Specifically, high resolution scanning transmission electron microscopy as well as elemental distribution analysis disclosed that H2 pretreatment successfully induced the formation of active Cu nanoparticles which uniformly dispersed on amorphous ZnO layer, whereas CO pretreatment led to the reconstruction of Cu nanoparticles/cluster, resulting in the formation of CuCx nanofibers under the high temperature reaction environment. The catalytic activity of the H2-treated CuZnOx/mSi-H2 is about three times higher than that of the CO-treated CuZnOx/mSi-CO for methanol synthesis. This gas atmosphere induced catalyst reconstruction strategy might pave the way for the rational catalyst design with precise active phase.

Unveiling anion induced surface reconstruction of perovskite oxide for efficient water oxidation

Perovskite oxides are a promising family of oxygen evolution reaction (OER) electrocatalysts. However, rational design of surface reconstruction on perovskite oxides to achieve high intrinsic activity is still a daunting challenge. Here, we demonstrate a facile anion defect approach to activate the surface reconstruction of perovskite oxide for OER. Experimental and theoretical investigations reveal that fluorine incorporation into LaNi0.75Fe0.25O3 (LNFO) perovskite with low vacancy formation energy facilitates surface transformation kinetics, creating electrochemically active oxyhydroxide layer. The reconstruction induced oxyhydroxide-perovskite heterostructure, in turn, enables a reduced energy barrier of OER relative to the pristine perovskite. As a demo, the optimized fluorine incorporated LNFO electrocatalyst exhibits an excellent OER performance with a low overpotential of 292 mV at 10 mA cm-2, significantly superior to the pristine LNFO and the benchmark IrO2 electrocatalysts. This finding offers new insights into activating surface reconstruction on perovskite oxide by engineering anion defect for water oxidation.

Strong coupling effect induced surface reconstruction of CeF3–Ni3N to form CeF3–NiOOH for the oxygen evolution reaction

The electrocatalytically active interface in a heterostructure is extremely crucial to obtain optimum adsorption energy of intermediates (O*, OH*, and HOO*) and faster electron transfer.

Surface Reconstruction of Iridium Nanoparticles for Enhanced Oxygen Evolution Reaction in Alkaline Medium

An electrochemical water splitting is a promising technology that can generate green hydrogen using renewable energy sources. However, the sluggish oxygen evolution reaction (OER) in an anodic side hinders their large scale applications. Many efforts have been focused on developing efficient electrocatalysts; iridium-based catalysts have gained much attentions due to remarkable intrinsic activities and high stability. Technically, however, the properties are derived from amorphous iridium oxide (IrOx) rather than metallic Ir. During an electrochemical activation process, the Ir metal is easily converted into oxidized species with multiple oxidation states of iridium, which are highly active toward OER. Similarly, many catalysts undergo changes during OER process (e.g., oxidation of precatalysts), resulting in enhancement of activities for OER beyond corresponding original catalysts. Accordingly, the reconstruction process involving surface oxidation and leaching of metal cations should be investigated to develop efficient OER electrocatalysts.Herein, we prepared chalcogen atom modified Ir/IrOx core/shell nanoparticles for enhanced alkaline OER performances (electrolyte: 1M KOH). The S-modified Ir/IrOx exhibited remarkable OER performances with current density of 10 mA cm−2 at overpotentials as low as 180 mV. Incorporation of chalcogen atoms induce surface reconstruction of the Ir/IrOx nanoparticles during OER measurements. It was observed that electrocatalytic activities of Ir/IrOx were varied depending on the type and concentration of chalcogen atoms. There were no observable morphological and structural changes in Ir/IrOx electrocatalyst, whereas the atomic ratio of chalcogen atoms noticeably decreased after OER tests. The result suggests that incorporated chalcogen atoms play a role in modifying the surface of Ir nanoparticles, rather than participating OER as active sites. In addition, XPS measurements were conducted in order to detect changes in chemical states of the catalysts during electrochemical process. We thus believe that the chalcogen atom induced surface reconstruction can be the strategy to efficiently improve the various electrochemical reactions.

Fluorine induced surface reconstruction of perovskite ferrite oxide as cathode catalyst for prolong-life Li-O2 battery

Lithium-oxygen batteries are widely studied because of the highest theoretical specific energy density among candidates for next-generation energy storage devices. However, the insulated bulk Li2O2 generated during discharge restricts their further development. Here, we demonstrate a surface reconstruction strategy on perovskite La0.8Fe0.9Co0.1O3-δ(LFCO) to construct a LaF3/LFCO composite, which induces a modified surface and also manipulates the electronic structure. The optimized surface and electronic structure adjust the discharge reaction pathway and form thin petal-like F doped Li2O2, which have better conductivity compared to traditional discharge product and benefit for Li-O2 battery performance. This LaF3/LFCO leads to much better cycle stability (157 vs 57 cycles) in comparison to the pristine LFCO. This work suggests surface reconstruction provides a new approach in the design of cathode catalyst for long-life lithium-oxygen battery.

Reprogramming thermodynamic-limiting oxidation cycle in NiFe-based oxygen evolution electrocatalyst through Mo doping induced surface reconstruction

Engineering of robust nonprecious electrocatalysts toward anodic oxygen evolution reaction (OER) is of great significance for lowering the cost and energy consumption for renewable fuel production. Herein, we report NiFeMoOx nanosheets as high-performance OER electrocatalyst through promoting the thermodynamic-limiting oxidation cycle process in NiFe oxyhydroxide via high-valence Mo doping. The NiFeMoOx nanosheets are prepared by an elaborate in-situ solvothermal etching-depositing process with NiFe alloy framework as substrate and metal precursors. The resultant nanosheets exhibit outstanding alkaline OER activity, requires only 235/282/327 mV overpotentials to achieve current density of 10/100/300 mA cm−2, respectively, with a good long-term stability at 20 mA cm−2 for 72 h. Besides, the Tafel slope low to 28.1 mV dec−1 indicates a favorable OER kinetics. The superior catalytic activity of NiFeMoOx nanosheets should be attributed to the lower oxidation states of Ni and Fe induced by high-valence dopant, leading to easier surface reconstruction at low charge oxidation cycling during OER, thereby effectively reducing the overpotential. The synergy between the electronic effect among multimetallic sites and the unique morphology is expected to inspire the development of robust OER electrocatalyst for industrial application.

Toward understanding the role of the electric double layer structure and electrolyte effects on well-defined interfaces for electrocatalysis

The interplay between the structure and composition of the electric double layer and the surface charge controls the electrocatalytic activity of reactions central to decarbonization of chemical fuels and materials. The employed electrolyte can affect the charge distribution and the electric field on the interface, which also alters the local pH and ordering of the water-solvent network. Additionally, the electrolyte plays a key role in stabilizing or destabilizing the adsorbed intermediates via non-covalent bonds, or poisons the surface and induces surface reconstruction, affecting the reactivity of the active sites positions. Herein, we discuss, from an experimental perspective, electrolyte effects on different interfacial properties relevant to electrocatalysis.

Synergistic Effects of V and Ni Catalysts on Hydrogen Sorption Kinetics of Mg-Based Hydrogen Storage Materials: A Computational Study

Adding transition metals (TMs) in Mg-based hydrogen storage materials has been proposed as a promising approach to improve their storage performance. It was experimentally shown that adding Ni and V catalysts in Mg dramatically decreased the formation enthalpies and activation energies of hydrogenation and dehydrogenation. Herein, we aim to unravel the roles of Ni and V catalysts in improving the hydrogen absorption process in Mg-based storage materials using first-principles methods. Mg2Ni and V clusters deposited on Mg2Ni structures were modeled, as evidenced by experimental observations. The results indicate that both V and Ni facilitate spontaneous H2 dissociation and stabilize hydrogen adsorption. Such strong interactions stem from the strong hybridization between the molecular orbital of adsorbed hydrogen and the Ni and V 3d states. The addition of the V cluster on the Mg2Ni surface also induces surface reconstruction, and consequently, more strong adsorption sites are available and the sites with connected Ni are formed, which could promote more facile diffusion paths of hydrogen spillover from the cluster to the surface and surface diffusion. Although hydrogen diffusion to a subsurface is the most kinetically limited step at low hydrogen contents, increasing hydrogen coverages reduces such barriers by a half. The high hydrogen coverage also drives surface, subsurface, and under-subsurface diffusion to be highly thermodynamically favorable. The computational results suggest that hydrogen absorption into the V/Mg2Ni material is kinetically and thermodynamically appreciable at operating conditions of high H2 pressure. The catalytic roles of Ni and V for the hydrogen absorption process also agree with the phenomenon seen in ab initio molecular dynamics simulations where the hydrogen absorption process occurs at a significantly faster rate on the Mg2Ni structure and even faster on the V/Mg2Ni structure compared to the pure Mg structure. Through systematic computational investigations, our findings provide in-depth theoretical insights and guidance on using a combination of TM catalysts to improve the performance of Mg-based hydrogen storage materials.

Electrochemically induced surface reconstruction of Ni-Co oxide nanosheet arrays for hybrid supercapacitors.

Transition metal oxides (TMOs) are promising materials for supercapacitors (SCs) because of their high theoretical capacity. However, their finite active sites and poor electrical conductivity lead to reluctant electrochemical performance. Herein, we report a facile electrochemical activation (ECA) method to boost the electrochemical activity of Ni-Co oxide nanosheet arrays (NiCoO NSA) for SCs. Specifically, honeycomb-like NiCoO NSA that was made through a solvothermal method followed by air annealing was activated by simply exerting certain cyclic voltammetry scans (the activated sample is named ac-NiCoO NSA). We have found this treatment results in dramatic surface structure change, forming numerous sub-nanostructures (nanoparticles and nano-leaves) on the NiCoO nanosheets. Rich antisite defects and oxygen vacancies in the NiCoO spinel phase were also created by the ECA treatment. Consequently, the ac-NiCoO NSA delivered a maximum capacity of 206.5 mAh g-1 (0.5 A g-1), which is about three times of the NiCoO NSA without treatment. A hybrid SC based on the ac-NiCoO NSA demonstrated excellent energy storage capacity (power density of 17.3kW kg-1 and energy density of 45.4Wh kg-1) and outstanding cyclability (>20,000 cycles, 77.4% retention rate). Our method provides a simple strategy for fabricating high performance TMOs for electrical energy storage devices like SCs.

Trace oxophilic metal induced surface reconstruction at buried RuRh cluster interfaces possesses extremely fast hydrogen redox kinetics

Developing high-efficiency electrocatalysts is the key to generating and consuming hydrogen by accelerating the reaction kinetics of the hydrogen oxidation and evolution reactions (HOR/HER). Although the kinetics process of the adsorbed intermediates (Had)-water-oxophilic metal has been investigated in the alkaline media, the hydroxyl species (Had or OH- or OHad)-activity relationship for oxophilic metal alloy electrocatalysis during multiple HOR and HER processes is still unclear. In this regard, our density functional theory (DFT) calculation results show that, due to partial substitution of Ru (Rh) clusters at buried interfaces by oxophilic-metal (OM) species, the long-range order of Ru (Rh) clusters surface atoms can be broken, and then the active atom reconstruction at buried interfaces is triggered, which decreases the oxidation intermediates of Ru (Rh) and gives rise to the increased activity for alkaline HER/HOR. At the same time, an OH--adsorption promoter forms, also favorable for OER. Encouraged by the first-principles calculation results, an ultralow-loaded OM species (0.13 wt% Co, 0.23 wt% Mn, 2.4 wt% Cr or 1.3 wt% Fe) incorporated RuRh cluster (RuRh-OM) catalyst is built by a mixed-solvent strategy. Impressively, after incorporating OM (Co; Mn; Cr and Fe), these catalysts exhibit higher HOR activity than pristine RuRh and commercial Pt even at higher potentials in 0.1 M KOH solutions, which outperforms most reported HOR catalysts and ~ 2 times higher than that of commercial Pt. Meanwhile, RuRh-Co also exhibits the highest HER activity among all reported Ru-based HER catalysts, and greatly improved OER and overall water spitting performances in alkaline solutions (1 M KOH for HER and overall water spitting, 0.1 M KOH for OER), exceeding RuRh and commercial noble metal catalysts.

Tailoring the Local Environment of Platinum in Single-Atom Pt1 /CeO2 Catalysts for Robust Low-Temperature CO Oxidation.

A single-atom Pt1 /CeO2 catalyst formed by atom trapping (AT, 800 °C in air) shows excellent thermal stability but is inactive for CO oxidation at low temperatures owing to over-stabilization of Pt2+ in a highly symmetric square-planar Pt1 O4 coordination environment. Reductive activation to form Pt nanoparticles (NPs) results in enhanced activity; however, the NPs are easily oxidized, leading to drastic activity loss. Herein we show that tailoring the local environment of isolated Pt2+ by thermal-shock (TS) synthesis leads to a highly active and thermally stable Pt1 /CeO2 catalyst. Ultrafast shockwaves (>1200 °C) in an inert atmosphere induced surface reconstruction of CeO2 to generate Pt single atoms in an asymmetric Pt1 O4 configuration. Owing to this unique coordination, Pt1 δ+ in a partially reduced state dynamically evolves during CO oxidation, resulting in exceptional low-temperature performance. CO oxidation reactivity on the Pt1 /CeO2 _TS catalyst was retained under oxidizing conditions.

Tailoring the Local Environment of Platinum in Single‐Atom Pt1/CeO2 Catalysts for Robust Low‐Temperature CO Oxidation

AbstractA single‐atom Pt1/CeO2 catalyst formed by atom trapping (AT, 800 °C in air) shows excellent thermal stability but is inactive for CO oxidation at low temperatures owing to over‐stabilization of Pt2+ in a highly symmetric square‐planar Pt1O4 coordination environment. Reductive activation to form Pt nanoparticles (NPs) results in enhanced activity; however, the NPs are easily oxidized, leading to drastic activity loss. Herein we show that tailoring the local environment of isolated Pt2+ by thermal‐shock (TS) synthesis leads to a highly active and thermally stable Pt1/CeO2 catalyst. Ultrafast shockwaves (>1200 °C) in an inert atmosphere induced surface reconstruction of CeO2 to generate Pt single atoms in an asymmetric Pt1O4 configuration. Owing to this unique coordination, Pt1δ+ in a partially reduced state dynamically evolves during CO oxidation, resulting in exceptional low‐temperature performance. CO oxidation reactivity on the Pt1/CeO2_TS catalyst was retained under oxidizing conditions.

Revisiting Optical Reflectance from Au(111) Electrode Surfaces with Combined High-Energy Surface X-ray Diffraction

We have combined high-energy surface X-ray diffraction (HESXRD) with 2D surface optical reflectance (2D-SOR) to perform in situ electrochemical measurements of a Au(111) electrode in 0.1 M HClO4 electrolyte. We show that electrochemically induced changes to Au(111) surface during cyclic voltammetry can be simultaneously observed with 2D-SOR and HESXRD. We discuss how small one atom high 1x1 islands, accommodating excess atoms after the lifting of the surface reconstruction, can lead to discrepancies between the two techniques. The use of HESXRD allows us to simultaneously detect parts of the truncation rods from the (1 × 1) surface termination and the p x √3 electrochemically induced surface reconstruction, during cyclic voltammetry. The presence of reconstruction phenomena is shown to not depend on having an ideally prepared surface and can in fact be observed after going to very oxidizing potentials. 2D-SOR can also detect the oxidation of the Au surface, however no oxide peaks are detected in the HESXRD signal, which is evidence that any Au oxide is X-ray amorphous.

Amorphous High-entropy Non-precious metal oxides with surface reconstruction toward highly efficient and durable catalyst for oxygen evolution reaction

High-entropy materials (HEMs) have attracted extensive interests in exploring multicomponent systems for highly efficient and durable catalysts. Tuning composition and configuration of HEMs provides untapped opportunities for accessing better catalytic performance. Herein, we report three amorphous high-entropy transition metal oxides catalysts with uniform composition through a simple and controllable liquid phase non-equilibrium reduction method. The self-made catalyst FeCoNiMnBOx exhibits excellent oxygen evolution performance, including a low overpotential (266 mV at 10 mA cm−2), small Tafel slope (64.5 mV dec-1) and extremely high stability (only 3.71% increase of potential after 100 h test and no current decay after cyclic voltammetry of 31,000 cycles). The outstanding performance can be attributed to the in-situ electrochemical activation induced surface reconstruction to form a stable oxyhydroxide surface layer, the cocktail effect (multi-metal synergy) brought by high entropy, and the advantages of amorphous structure itself. The outstanding catalytic properties of the new high-entropy amorphous metal oxide, as well as its advantages of low cost and simple preparation, suggest its great potential in water splitting.

The release of metal ions induced surface reconstruction of layered double hydroxide electrocatalysts

Developing highly efficient and affordable oxygen evolution reaction (OER) electrocatalysts is of great significance for the large-scale application of water splitting to produce hydrogen.