Enhanced Magnetic Heating for Efficient Oxygen Evolution Reaction by Pinning Effect of Ferromagnetic/Antiferromagnetic Coupling.

The magnetic heating effect under alternating magnetic fields (AMFs) has recently gained attention in catalysis due to its potential to greatly boost catalytic activities by providing localized heating around magnetic nanoparticles. However, nanoparticles still suffer from low magnetic heating efficiency due to their low magnetic anisotropy and thermal fluctuation, which is a key barrier in the wide application of AMF-assisted catalysis. Herein, by introducing the pinning effect of ferromagnetic/antiferromagnetic (FM/AFM) coupling, NiO/NiOOH (AFM/FM) core-shell nanoparticles exhibit significantly enhanced oxygen evolution reaction activity and resistance to thermal fluctuations under AMF, compared to NiOOH nanoparticles. Notably, magnetized NiO/NiOOH nanoparticles provide an overpotential of 186 mV at 10 mA cm-2, outperforming unmagnetized ones (218 mV) under the same conditions, further emphasizing the prominent role of the pinning effect in enhanced magnetic heating efficiency. This work provides valuable inspiration to design advanced magnetic catalysts and meet the challenge of the development of AMF-assisted catalysis.

Atomic Magnetic Heating Effect Enhanced Hydrogen Evolution Reaction of Gd@MoS2 Single-Atom Catalysts.

Atomic heating on single atoms (SAs) to maximize the catalytic efficiency of each active site would be a fascinating solution to break the bottleneck for the performance improvement of single-atom catalysts (SACs) but highly challenging task. Here, based on the Gd@MoS2 SACs synthesized by a facile laser molecular beam epitaxy method, high-frequency alternating magnetic field (AMF) technology is employed to induce atomic magnetic heating on Gd SAs that is meanwhile demonstrated to be the catalytic active center. Significant improvement in catalytic kinetics under AMF excitation (3.9 mT) is achieved, yielding a remarkable enhancement of hydrogen evolution reaction magnetothermal-current by ≈924%. Through theoretical calculations and spin-related electrochemical experiments, such promotion in catalyst activity can be attributed to spin flip (or canting) in Gd SAs leading to the atomic magnetic heating effect on catalytic active center. Together with the embodied high stability, the implement of AMF to the SAs field is demonstrated in this work, and the precisely atomic magnetic heating on specific SAs offers unprecedented thinking for further improvement of SACs performance in the future.

Electrochemical Reconstruction of NiFe/NiFeOOH Superparamagnetic Core/Catalytic Shell Heterostructure for Magnetic Heating Enhancement of Oxygen Evolution Reaction.

Although (oxy)hydroxides generated by electrochemical reconstruction (EC-reconstruction) of transition-metal catalysts exhibit highly catalytic activities, the amorphous nature fundamentally impedes the electrochemical kinetics due to its poor electrical conductivity. Here, EC-reconstructed NiFe/NiFeOOH core/shell nanoparticles in highly conductive carbon matrix based on the pulsed laser deposition prepared NiFe nanoparticles is successfully confined. Electrochemical characterizations and first-principles calculations demonstrate that the reconstructed NiFe/NiFeOOH core/shell nanoparticles exhibit high oxygen evolution reaction (OER) electrocatalytic activity (a low overpotential of 342.2 mV for 10 mA cm-2 ) and remarkable durability due to the efficient charge transfer in the highly conductive confined heterostructure. More importantly, benefit from the superparamagnetic nature of the reconstructed NiFe/NiFeOOH core/shell nanoparticles, a large OER improvement is achieved (an ultralow overpotential of 209.2 mV for 10 mA cm-2 ) with an alternating magnetic field stimulation. Such OER improvement can be attributed to the Néel relaxation related magnetic heating effect functionalized superparamagnetic NiFe cores, which are generally underutilized in reconstructed core/shell nanoparticles. This work demonstrates that the designed superparamagnetic core/shell nanoparticles, combined with the large improvement by magnetic heating effect, are expected to be highly efficient OER catalysts along with the confined structure guaranteed high conductivity and catalytic stability.

External Fields Assisted Highly Efficient Oxygen Evolution Reaction of Confined 1T-VSe2 Ferromagnetic Nanoparticles.

As a clean and effective approach, the introduction of external magnetic fields to improve the performance of catalysts has attracted extensive attention. Owing to its room-temperature ferromagnetism, chemical stability, and earth abundance, VSe2 is expected to be a promising and cost-effective ferromagnetic electrocatalyst for the accomplishment of high-efficient spin-related OER kinetics. In this work, a facile pulsed laser deposition (PLD) method combined with rapid thermal annealing (RTA) treatment is used to successfully confine monodispersed 1T-VSe2 nanoparticles in amorphous carbon matrix. As expected, with external magnetic fields of 800 mT stimulation, the confined 1T-VSe2 nanoparticles exhibit highly efficient oxygen evolution reaction (OER) catalytic activity with an overpotential of 228 mV for 10 mA cm-2 and remarkable durability without deactivation after >100 h OER operation. The experimental results together with theoretical calculations illustrate that magnetic fields can facilitate the surface charge transfer dynamics of 1T-VSe2 , and modify the adsorption-free energy of *OOH, thus finally improving the intrinsic activity of the catalysts. This work realizes the application of ferromagnetic VSe2 electrocatalyst in highly efficient spin-dependent OER kinetics, which is expected to promote the application of transition metal chalcogenides (TMCs) in external magnetic field-assisted electrocatalysis.

Alternating Magnetic Field Induced Magnetic Heating in Ferromagnetic Cobalt Single-Atom Catalysts for Efficient Oxygen Evolution Reaction.

Alternating magnetic field (AMF) is a promising methodology for further improving magnetic single-atom catalyst (SAC) activity toward oxygen evolution reaction (OER). Herein, the anchoring of Co single atoms on MoS2 support (Co@MoS2), leading to the appearance of in-plane room-temperature ferromagnetic properties, is favorable for the parallel spin arrangement of oxygen atoms when a magnetic field is applied. Moreover, field-assisted electrocatalytic experiments confirmed that the spin direction of Co@MoS2 is changing with the applied magnetic field. On this basis, under AMF, the active sites in ferromagnetic Co@MoS2 were heated by exploiting the magnetic heating generated from spin polarization flip of these SACs to further expedite OER efficiency, with overpotential at 10 mA cm-2 reduced from 317 mV to 250 mV. This work introduces a feasible and efficient approach to enhance the OER performance of Co@MoS2 by AMF, shedding some light on the further development of magnetic SACs for energy conversion.

Synergistically Coupling of Manganese-Doped CoP Nanowires Arrays with Highly Dispersed Ni(PO3)2 Nanoclusters toward Efficient Overall Water Splitting.

Co-based phosphides are considered to be highly promising electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, their electrocatalytic efficiencies are greatly limited by the weak water dissociation process and unsatisfactory adsorption ability toward reaction intermediates. Herein, novel Mn-doped CoP/Ni(PO3)2 heterostructure array electrocatalysts which are composed of highly dispersed Ni(PO3)2 nanoclusters that are tightly wrapped on Mn-doped CoP nanowire arrays are designed. An electrocatalytic performance test suggested that the heterostructure arrays exhibited competitive electrocatalytic performance toward both HER and OER, which needed overpotentials of 116 and 245 mV to drive a current of 10 mA/cm2, respectively. Encouragingly, a symmetric two electrode water splitting system constructed by the heterostructure arrays required an ultralow cell voltage, suggesting the potential in overall water splitting. First-principles calculations combined with experimental characterization were further performed to clarify the electrocatalytic mechanism. On the one hand, effective doping of Mn atoms could optimize the surface electronic structure of CoP and promote the intrinsic activity. On the other hand, the compact and abundant heterogeneous interface between Ni(PO3)2 and CoP not only made more active sites exposed but also promoted the effective adsorption of intermediate reaction species on the catalyst surface. This work provides a new strategy to improve electrocatalytic performance of Co-based phosphides through the synergistic coupling of metal-doping and phosphate surface decoration, which will greatly promote the development of highly efficient electrocatalysts for overall water splitting.

Boosting the OER Performance of Nitrogen-Doped Ni Nanoclusters Confined in an Amorphous Carbon Matrix.

Nanoclusters are ideal electrocatalysts due to their high surface activity. However, their high activities also lead to serious agglomeration and performance attenuation during the catalytic process. Here, highly dispersed Ni nanoclusters (∼3 nm) confined in an amorphous carbon matrix are successfully fabricated by pulsed laser deposition, followed by rapid temperature annealing treatment. Then, the Ni nanoclusters are further doped with nitrogen element through a clean N2 radio frequency plasma technology. It is found that the nitrogen-doped Ni nanoclusters obtained under optimized conditions showed superior OER performance with a very low overpotential of 240 mV at a current density of 10 mA/cm2, together with good stability. The excellent OER performance of the nanoclusters can be attributed to the unique confined structure and nitrogen doping, which not only provide more active sites but also improve the conductivity. Our work provides a controllable method for the construction of a novel confined structure with controllable nitrogen doping, which can be used as a high-efficiency OER electrocatalyst.

Efficient Charge Transfers in Highly Conductive Copper Selenide Quantum Dot-Confined Catalysts for Robust Oxygen Evolution Reaction.

Defective quantum dots (QDs) are the emerging materials for catalysis by virtue of their atomic-scale size, high monodispersity, and ultra-high specific surface area. However, the dispersed nature of QDs fundamentally prohibits the efficient charge transfer in various catalytic processes. Here, we report efficient and robust electrocatalytic oxygen evolution based on defective and highly conductive copper selenide (CuSe) QDs confined in an amorphous carbon matrix with good uniformity (average diameter 4.25 nm) and a high areal density (1.8 × 1012 cm-2). The CuSe QD-confined catalysts with abundant selenide vacancies were prepared by using a pulsed laser deposition system benefitted by high substrate temperature and ultrahigh vacuum growth conditions, as evidenced by electron paramagnetic resonance characterizations. An ultra-low charge transfer resistance (about 7 Ω) determined by electrochemical impedance spectroscopy measurement indicates the efficient charge transfer of CuSe quantum-confined catalysts, which is guaranteed by its high conductivity (with a low resistivity of 2.33 µΩ·m), as revealed by electrical transport measurements. Our work provides a universal design scheme of the dispersed QD-based composite catalysts and demonstrates the CuSe QD-confined catalysts as an efficient and robust electrocatalyst for oxygen evolution reaction.

Field-Free Improvement of Oxygen Evolution Reaction in Magnetic Two-Dimensional Heterostructures.

Ferromagnetic (FM) electrocatalysts have been demonstrated to reduce the kinetic barrier of oxygen evolution reaction (OER) by spin-dependent kinetics and thus enhance the efficiency fundamentally. Accordingly, FM two-dimensional (2D) materials with unique physicochemical properties are expected to be promising oxygen-evolution catalysts; however, related research is yet to be reported due to their air-instabilities and low Curie temperatures (TC). Here, based on the synthesis of 2D air-stable FM Cr2Te3 nanosheets with a low TC around 200 K, room-temperature ferromagnetism is achieved in Cr2Te3 by proximity to an antiferromagnetic (AFM) CrOOH, demonstrating the accomplishment of long-ranged FM ordering in Cr2Te3 because the magnetic proximity effect stems from paramagnetic (PM)/AFM heterostructure. Therefore, the OER performance can be permanently promoted (without applied magnetic field due to nonvolatile nature of spin) after magnetization. This work demonstrates that a representative PM/AFM 2D heterostructure, Cr2Te3/CrOOH, is expected to be a high-efficient magnetic heterostructure catalysts for oxygen-evolution.

MoS2 Nanoribbons with a Prolonged Photoresponse Lifetime for Enhanced Visible Light Photoelectrocatalytic Hydrogen Evolution.

The high recombination rate of photoinduced electron-hole pairs limits the hydrogen production efficiency of the MoS2 catalyst in photoelectrochemical (PEC) water splitting. The strategy of prolonging the lifetime of photoinduced carriers is of great significance to the promotion of photoelectrocatalytic hydrogen production. An ideal approach is to utilize edge defects, which can capture photoinduced electrons and thus slow down the recombination rate. However, for two-dimensional MoS2, most of the surface areas are inert basal planes. Here, a simple method for preparing one-dimensional MoS2 nanoribbons with abundant inherent edges is proposed. The MoS2 nanoribbon-based device has a good spectral response in the range of 400-500 nm and has a longer lifetime of photoinduced carriers than other MoS2 nanostructure-based photodetectors. An improved PEC catalytic performance of these MoS2 nanoribbons is also experimentally verified under the illumination of 405 nm by using the electrochemical microcell technique. This work provides a new strategy to prolong the lifetime of photoinduced carriers for further improvement of PEC activity, and the evaluation of photoelectric performance provides a feasible way for transition-metal dichalcogenides to be widely used in the energy field.

Highly Mesoporous Cobalt-Hybridized 2D Cu3P Nanosheet Arrays as Boosting Janus Electrocatalysts for Water Splitting.

Recently, developing economical electrocatalysts with high performance in water decomposition has become a research hotspot. Herein, two kinds of cobalt-hybridized Cu3P nanostructure array electrocatalysts (including highly mesoporous 2D nanosheets and sugar gourd-like 1D nanowires) were controllably grown on a nickel foam substrate through a simple hydrothermal method combined with a subsequent phosphating treatment method. An electrocatalytic test indicated that the as-prepared 2D nanosheet array exhibited excellent activity and stability toward hydrogen evolution reaction under alkaline conditions, which offered a low overpotential of 99 mV at 10 mA/cm2 and a small Tafel slope of 70.4 mV/dec, whereas a competitive overpotential of 272 mV was required for oxygen evolution reaction. In addition, the 2D nanosheet array delivered a low cell voltage of 1.66 V at 10 mA/cm2 in a symmetric two-electrode system, implying its huge potential in overall water decomposition. The electrocatalytic performance is superior to the as-prepared 1D nanowire array and most of the Cu3P-related electrocatalysts previously reported. Experimental measurements and first-principles calculations show that the excellent performance of the 2D nanosheet array can be attributed to its unique 2D mesoporous structure and hybridization of cobalt, which not only provide a large electrochemically active surface and fast electrocatalytic reaction kinetics but also weaken the binding strength of electrocatalytic reaction intermediates. The present study provides a simple and controllable approach to synthesize Cu3P-based bimetallic phosphide nanostructures, which can be used as boosting Janus electrocatalysts for water decomposition.

Active Site Engineering in CoP@NC/Graphene Heterostructures Enabling Enhanced Hydrogen Evolution.

As the core of an electrocatalyst, the active site is critical to determine its catalytic performance in the hydrogen evolution reaction (HER). In this work, porous N-doped carbon-encapsulated CoP nanoparticles on both sides of graphene (CoP@NC/GR) are derived from a bimetallic metal-organic framework (MOF)@graphene oxide composite. Through active site engineering by tailoring the environment around CoP and engineering the structure, the HER activity of CoP@NC/GR heterostructures is significantly enhanced. Both X-ray photoelectron spectroscopy (XPS) results and density functional theory (DFT) calculations manifest that the electronic structure of CoP can be modulated by the carbon matrix of NC/GR, resulting in electron redistribution and a reduction in the adsorption energy of hydrogen (ΔGH*) from -0.53 to 0.04 eV. By engineering the sandwich-like structure, active sites in CoP@NC/GR are further increased by optimizing the Zn/Co ratio in the bimetallic MOF. Benefiting from this active site engineering, the CoP@NC/GR electrocatalyst exhibits small overpotentials of 105 mV in 0.5 M H2SO4 (or 125 mV in 1 M KOH) to 10 mA cm-2, accelerated HER kinetics with a low Tafel slope of 47.5 mV dec-1, and remarkable structural and HER stability.

General synthesis of mixed-dimensional van der Waals heterostructures with hexagonal symmetry.

The combination of two-dimensional (2D) materials with non-2D materials (quantum dots, nanowires and bulk materials), i.e. mixed-dimensional van der Waals (md-vdW) heterostructures endow 2D materials with remarkable electronics properties. However, it remains a big challenge to synthesize md-vdW heterostructures because of the difference of crystal symmetry between 2D and non-2D materials. Meanwhile, it is difficult to initiate the nucleation due to the lack of chemical active sites on chemical inert surfaces of 2D materials. Herein, we design a general chemical vapor deposition method for synthesizing a broad class of md-vdW heterostructures with well-aligned hexagonal symmetry including MoS2/FeS, MoS2/CoS, MoS2/MnS, MoS2/ZnS, Mo(SxSe1-x)2/ZnSxSe1-x, Mo(SxSe1-x)2/CdSxSe1-x. Combining with DFT calculation, we find that the hexagonal symmetry and the centered clusters of MoS2and Mo(SxSe1-x)2nanoflakes are two crucial factors to launch the hexagonally oriented growth and nucleation of non-2D materials on 2D materials. Our discovery opens an opportunity for the versatile hetero-integration of 2D materials and allows systematic investigation of physical properties in a wide variety of md-vdW heterostructures.

Magnetic Enhancement for Hydrogen Evolution Reaction on Ferromagnetic MoS2 Catalyst.

Numerous efforts in improving the hydrogen evolution reaction (HER) performance of transition metal dichalcogenides mostly focus on active sites exposing, vacancy engineering, and phase engineering. However, little room is left for improvement in these approaches. It should be noted that efficient electron transfer also plays a crucial role in catalytic activity. In this work, by employment of an external vertical magnetic field, ferromagnetic bowl-like MoS2 flakes can afford electrons transmitting easily from a glassy carbon electrode to active sites to drive HER, and thus perform magnetic HER enhancement. The ferromagnetic bowl-like MoS2 flakes with an external vertical magnetic field can provide a roughly doubled current density compared to that without an external vertical magnetic field at a constant overpotential of -150 mV. Our work may provide a new pathway to break the bottleneck for further improvement of HER performance and also paves the way to utilize the magnetic enhancement in widely catalytic application.

Tunable Surface Selenization on MoO2 -Based Carbon Substrate for Notably Enhanced Sodium-Ion Storage Properties.

Transition metal chalcogenides with high theoretical capacity are promising conversion-type anode materials for sodium ion batteries (SIBs), but often suffer from unsatisfied cycling stability (hundreds of cycles) caused by structural collapse and agglomerate. Herein, a rational strategy of tunable surface selenization on highly crystalline MoO2 -based carbon substrate is designed, where the sheet-like MoSe2 can be coated on the surface of bundle-like N-doped carbon/granular MoO2 substrate, realizing partial transformation from MoO2 to MoSe2 , and creating b-NC/g-MoO2 @s-MoSe2 -10 with robust hierarchical MoO2 @MoSe2 heterostructures and strong chemical couplings (MoC and MoN). Such well-designed architecture can provide signally improved reaction kinetics and reinforced structural integrity for fast and stable sodium-ion storage, as confirmed by the ex situ results and kinetic analyses as well as the density functional theory calculations. As expected, the b-NC/g-MoO2 @s-MoSe2 -10 delivers splendid rate capability and ultralong cycling stability (254.2 mAh g-1 reversible capacity at 5.0 A g-1 after 6000 cycles with ≈89.0% capacity retention). Therefore, the tunable surface strategy can provide new insights for designing and constructing heterostructures of transition metal chalcogenides toward high-performance SIBs.

FKBP8 inhibits virus-induced RLR-VISA signaling.

The mitochondrial antiviral signal protein mitochondrial antiviral signaling protein, also known as virus-induced signaling adaptor (VISA), plays a key role in regulating host innate immune signaling pathways. This study identifies FK506 binding protein 8 (FKBP8) as a candidate interacting protein of VISA through the yeast two-hybrid technique. The interaction of FKBP8 with VISA, retinoic acid inducible protein 1 (RIG-I), and IFN regulatory factor 3 (IRF3) was confirmed during viral infection in mammalian cells by coimmunoprecipitation. Overexpression of FKBP8 using a eukaryotic expression plasmid significantly attenuated Sendai virus-induced activation of the promoter interferons ß (IFN-ß), and transcription factors nuclear factor κ-light chain enhancer of activated B cells (NF-κB) and IFN-stimulated response element (ISRE). Overexpression of FKBP8 also decreased dimer-IRF3 activity, but enhanced virus replication. Conversely, knockdown of FKBP8 expression by RNA interference showed opposite effects. Further studies indicated that FKBP8 acts as a negative interacting partner to regulate RLR-VISA signaling by acting on VISA and TANK binding kinase 1 (TBK1). Additionally, FKBP8 played a negative role on virus-induced signaling by inhibiting the formation of TBK1-IRF3 and VISA-TRAF3 complexes. Notably, FKBP8 also promoted the degradation of TBK1, RIG-I, and TRAF3 resulting from FKBP8 reinforced Sendai virus-induced endogenous polyubiquitination of RIG-I, TBK1, and TNF receptor-associated factor 3 (TRAF3). Therefore, a novel function of FKBP8 in innate immunity antiviral signaling regulation was revealed in this study.

Two-photon and three-photon absorption in ZnO nanocrystals embedded in Al2O3 matrix influenced by defect states.

The broadband nonlinear absorption in ZnO nanocrystals embedded in Al2O3 matrix was investigated by Z-scan and pump-probe techniques from 400 nm to 800 nm. The effective two-photon absorption and three-photon absorption coefficients were determined to be ∼1.1×103 cm/GW at 400 nm and ∼1.1×10-1 cm3/GW2 at 800 nm, respectively, which are at least two orders of magnitude greater than that in ZnO bulk crystal. It may be attributed to the defect-states-mediated multiphoton absorption process, which was proofed by comparison experiments with different densities of interfacial defect states. The corresponding lifetimes for the intraband relaxation, defect-states trapping, and interband recombination processes were measured by femtosecond transient absorption measurements as τ1 ∼ 1 ps, τ2 ∼ 13 ps, and τ3 ∼ 350 ps, respectively.

Improved ethanol gas sensing performances of a ZnO/Co3O4 composite induced by its flytrap-like structure.

Nanocomposite materials with excellent receptor and transducer functions are promising in ameliorating their gas sensing properties. However, due to the abrupt changes of receptor and transducer functions when different components are combined together, structural engineering that considers both the receptor and transducer functions to design such desirable sensing materials still remains a great challenge. Here, a nanocomposite material composed of 1D ZnO nanorods and 3D Co3O4 microspheres assembled by single-crystalline porous nanosheets has been designed, which was inspired by the high-efficiency receptor-transducer-response structure of venus flytraps. The as-designed ZnO/Co3O4 composite exhibited high response (Ra/Rg = 125 to 100 ppm ethanol) which was 84 times and 8 times higher than those of Co3O4 (Rg/Ra = 1.43) and ZnO (Ra/Rg = 15). The excellent sensing properties are ascribed to the as-designed flytrap-like structure which possesses a super receptor function from 1D ZnO with a large surface area, p-n heterojunctions with an amplified response signal, as well as excellent transducer functions from single-crystalline porous Co3O4 with fast charge transport channels. This strategy provides us with new guidance on the exploration of high-performance gas sensors which could further extend to other bio-structures that are abundant in nature.

In-situ construction of direct Z-scheme NiO/Bi2MoO6 heterostructure arrays with enhanced room temperature ether sensing properties under visible light irradiation.

Light irradiation has emerged as a promising strategy to promote room temperature sensing of resistive-type semiconductor gas sensors recently. However, high recombination rate of photo-generated carriers and poor visible light response of conventional semiconductor sensing materials have greatly limited the further performance improvement. It is urgent to develop gas sensing materials with high photo-generated carrier separation efficiency and excellent visible light response. Herein, a novel direct Z-scheme NiO/Bi2MoO6 heterostructure arrays were designed and in-situ constructed on alumina flat substrate to form thin film sensors, which realized excellent room temperature gas response towards ether under irradiation of visible light for the first time, together with excellent stability and selectivity. Based on density functional theory calculation and experimental characterization, it was demonstrated that the construction of Z-scheme heterostructure could greatly promote the separation of photo-generated carriers and adsorption of ether. Moreover, the excellent visible light response characteristics of NiO/Bi2MoO6 could improve the utilization of visible light. In addition, the in-situ construction of array structure could avoid a series of problems caused by the conventional thick film devices. The work not only provides a promising guideline for Z-scheme heterostructure arrays in promoting the room temperature sensing performance of semiconductors gas sensors under visible light irradiation, but also clarifies the gas sensing mechanism of Z-scheme heterostructure at the atomic and electronic level.

Suppressed charge recombination via defect engineering of confined semiconducting quantum dots for photoelectrocatalysis.

Confined semiconducting CuSe quantum dots with abundant Se vacancies are synthesized by pulsed laser deposition with in situ vacuum annealing. With the presence of Se vacancies, the photogenerated charge recombination is suppressed by the self-introduced in-gap trapping states, thus enhancing the photoelectrocatalytic activity under solar illumination.