Charge Redistribution Research Articles

Molten Salt-Assisted Synthesis of Ferric Oxide/M-N-C Nanosheet Electrocatalysts for Efficient Oxygen Reduction Reaction.

Efficient, stable, and low-cost oxygen reduction catalysts are the key to the large-scale application of metal-air batteries. Herein, high-dispersive Fe2O3 nanoparticles (NPs) with abundant oxygen vacancies uniformly are anchored on lignin-derived metal-nitrogen-carbon (M-N-C) hierarchical porous nanosheets as efficient oxygen reduction reaction (ORR) catalysts (Fe2O3/M-N-C, M═Cu, Mn, W, Mo) based on a general and economical KCl molten salt-assisted method. The combination of Fe with the highly electronegative O induces charge redistribution through the Fe-O-M structure, thereby reducing the adsorption energy of oxygen-containing substances. The coupling effect of Fe2O3 NPs with M-N-C expedites the catalytic activity toward ORR by promoting proton generation on Fe2O3 and transfer to M-N-C. Experimental and theoretical calculation further revealed the remarkable electronic structure evolution of the metal site during the ORR process, where the emission density and local magnetic moment of the metal atoms change continuously throughout their reaction. The unique layered porous structure and highly active M-N4 sites resulted in the excellent ORR activity of Fe2O3/Cu-N-C with the onset potential of 0.977V, which is superior to Pt/C. This study offers a feasible strategy for the preparation of non-noble metal catalysts and provides a new comprehension of the catalytic mechanism of M-N-C catalysts.

The first principle calculations of band offsets among Cs2(Ti, Zr, Hf)X6 double halide perovskites

This study investigates the band offsets among Cs2(Ti, Zr, Hf)X6 double halide perovskites. Valence band offsets (VBO) and conduction band offsets (CBO) were calculated using density functional theory (DFT) with the Perdew–Burke-Ernzerhof (PBE) functional and the hybrid Heyd–Scuseria–Ernzerhof (HSE) functional, employing the supercell technique. This technique offers greater accuracy and reliability by explicitly calculating the potential differences at the interface. A critical factor influencing the results is the contribution of the dipole potential (VD), which induces shifts in the VBO and CBO by approximately 0.2 to 0.6 eV relative to values predicted by the electron affinity rule. This discrepancy arises from the inclusion of interface-specific effects, such as charge redistribution and polarization. Additionally, the findings indicate that the energy band alignments among these compounds are type-I within the same group of halides, with nearly identical lattice constants for Zr- and Hf-based compounds due to their similar ionic radii. These results provide valuable insights for the design of heterostructures in electronic applications and highlight the potential of Cs2(Ti, Zr, Hf)X6 compounds as efficient materials for solar cells, light-emitting diodes, and photodetectors.

A Janus Platinum/Tin Oxide Heterostructure for Durable Oxygen Reduction Reaction.

Designing efficient and durable electrocatalysts for oxygen reduction reaction (ORR) is essential for proton exchange membrane fuel cells (PEMFCs). Platinum-based catalysts are considered efficient ORR catalysts due to their high activity. However, the degradation of Pt species leads to poor durability of catalysts, limiting their applications in PEMFCs. Herein, a Janus heterostructure is designed for high durability ORR in acidic media. The Janus heterostructure composes of crystalline platinum and cassiterite tin oxide nanoparticles with carbon support (J-Pt@SnO2/C). Based on the synchrotron fine structure analysis and electrochemical investigation, the crystalline reconstruction and charge redistribution at the interface of Janus structure are revealed. The tightly coupled interface could optimize the valance states of Pt and the adsorption/desorption of oxygenated intermediates. As a result, the J-Pt@SnO2/C catalyst possesses distinguishing long-term stability during the accelerated durability test without obvious degradation after 40000 cycles and keeps the majority of activity after 70000 cycles. Meanwhile, the catalyst exhibits outstanding activity with half-wave potential at 0.905V and a mass activity of 0.355AmgPt -1 (2.7 times higher than Pt/C). The approach of the Janus catalyst paves an avenue for designing highly efficient and stable Pt-based ORR catalyst in the future implementation.

Oxygen Vacancies Regulated S-Scheme Charge Transport Route in BiVO4-OVs/g-C3N4 Heterojunction for Enhanced Photocatalytic Performance.

Oxygen vacancies (OVs) are widely considered as active sites in photocatalytic reactions, yet the crucial role of OVs in S-scheme heterojunction photocatalysts requires deeper understanding. In this work, OVs at hetero-interface regulated S-scheme BiVO4-OVs/g-C3N4 photocatalysts are constructed. The Fermi-level structures of BiVO4 and g-C3N4 lead to a redistribution of charges at the heterojunction interface, inducing an internal electric field at the interface, which tends to promote the recombination of photogenerated carriers at the interface. Importantly, the introduction of OVs induces defect electronic states in the BiVO4 bandgap, creating indirect recombination energy level that serves as crucial intermediator for photogenerated carrier recombination in the S-scheme heterojunction. As a result, the photocatalytic degradation rate on Rhodamine B (RhB) and tetracyclines (TCs) for the optimal sample is 10.7 and 11.8 times higher than the bare one, the photocatalytic hydrogen production rate is also improved to 558 µmol g-1 h-1. This work shows the importance of OVs in heterostructure photocatalysis from both thermodynamic and kinetic aspects and may provide new insight into the rational design of S-scheme photocatalysts.

Bifunctional Mott-Schottky-type Co-Fe3N electrocatalyst as sulfur host and separator modifier to enhance the transformation kinetics of Li2S

Recently, lithium-sulfur batteries (LSBs) with ultra-high theoretical energy density attract the attention of researchers. However, the shuttle of lithium polysulfides (LPSs) seriously restrict the development of LSBs. Here, Co-Fe3N with Mott-Schottky type exhibits exceptional chemisorption and catalytic capabilities towards LPSs. The Co-Fe3N Mott-Schottky heterojunction induces charge redistribution at the heterogeneous interface, thereby increasing the rate of charge transfer, enhancing chemisorption ability, and reducing the energy barrier for S8 reduction and Li2S oxidation. The Co metal provides more catalytic and adsorption active sites for the conversion of LPSs and further improves the catalytic activity of Fe3N. Under the synergistic effect of the metal Co and Fe3N, the redox reaction of LPSs is improved, and the nucleation/decomposition energy barriers of Li2S are decreased, realizing the multifunctional coupling of adsorption-catalytic-conversion of LPSs. The LSBs with Co-Fe3N/S cathode and Co-Fe3N-PP separator exhibits a low capacity decay of 0.067 % per cycle at 1 C during 400 cycles. Even at a high sulfur loading of 3.1 mg cm−2, the LSBs delivers a reversible capacity of 1016 mA h g−1 at 0.1 C. The utilization of the Co-Fe3N with Mott-Schottky type in LSBs presents a novel approach towards designing multifunctional coupled materials with adsorption-catalysis-conversion capabilities.

Investigating the efficacy of Palladium Doped Ceria for the Photodegradation of Azo Dyes

Ceria (CeO2) was prepared by microwave assisted precipitation method while sonothermal method was utilized for the synthesis of palladium doped ceria (Pd-CeO2) photocatalyst. HR-TEM analysis confirms the face centered cubic geometry (FCC) of CeO2. The particle size of Pd-CeO2 calculated from HR-TEM analysis (7.6±2.18 nm) is in close relation with XRD (8.25±0.25 nm). The SAED pattern of Pd-CeO2 shows the poly crystallinity where the d-spacing was 0.31 and 0.30 nm which corresponds to CeO2 and Pd crystal facets 111 and 100 respectively. The amount of dopant and existence of Pd, Ce and O was confirmed from EDX spectra and elemental mapping. BET surface area analysis of CeO2 (64.45 m2/g), Pd-CeO2 (60.20 m²/g) revealed that the decrease in the surface area of CeO2 due to Pd loading which is confirmed by pore volume (0.079 cm³/g) for CeO2 and pore volume for Pd-CeO2 (0.073 cm³/g). The photocatalytic activity of Pd-CeO2 was screened against a model azo dye Acid red-4 (AR-4). The fluctuation of the rate of photodegradation (PD) of AR-4 was observed under different reaction conditions. Therefore, the reaction parameters were optimized to achieve best catalytic activity up to PD; 98%. The kinetic study suggests that the PD of AR-4 follows 1st order kinetics with regression coefficient (R2=0.973) and rate constant (k=0.024/min). Recycling study revealed the prolong use of catalyst without significant loss of activity. DFT study and experiments revealed the synergism of Pd on the photo response of CeO2. Perhaps this synergistic effect due to metal support interaction, causes redistribution of charges and Fermi energy levels. The synthesized catalyst showed potential application for the treatment of textile industrial effluents.

Construction of 0-dimensional silver quantum dot/MoSe2@MXene/3-dimensional porous copper foam composite electrodes with heterogeneous interfaces for synergistic electrocatalytic degradation of antibiotics

This study proposes a novel and efficient Ag quantum dots (QDs)/MoSe2@two-dimensional transition metal carbide/nitride (MXene)/copper foam (CF) composite electrode to address the challenge of electrocatalytic degradation of antibiotics in water. The electrode formed a unique electron donor–acceptor system by loading Ag QDs and heterostructured nanosheets on CF, significantly facilitating charge transfer and segregation at the interface. The catalytically active sites at the edges and defective locations of MoSe2 in conjunction with the two-dimensional MXene structure, which formed an efficient electron transfer channel, promoted the electron transfer from the interior to the surface and accelerated the hydrogen adsorption and reduction reactions. Moreover, the charge redistribution at the interface of Ag QDs and MoSe2@MXene formed interfacial dipoles, increasing the active sites on the catalyst surface and promoting the generation of cathodic atomic hydrogen (H*). Under optimal conditions, the degradation rate of tigecycline (TGC) reached as high as 90.1 % ± 2.4 % within 60 min. The anode-generated OH and HClO, along with the cathode-generated H, further promoted the degradation of TGC through co-catalysis. The degradation pathways were analyzed using density-functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC-MS) techniques. Moreover, toxicity analysis of the degradation products was carried out to ensure the safety of the treated wastewater discharge. A reflux continuous effluent reactor was also designed to achieve high degradation efficiency and low energy consumption after stable operation, laying the foundation for industrial applications. This technology provides new ideas for the design of green, efficient, stable, and low-consumption electrocatalytic reactors and contributes to a sustainable future environment.

Effects of N, O, S on generalized stacking fault energies and dislocation movements in γ-Ni and γ′-Ni3Al

The effects of interstitial atoms (N, O and S) on generalized stacking fault energies in the γ-Ni and γ′-Ni3Al with were systematically elucidated by first-principles calculations. N, O and S atoms had the preference for octahedral interstitial sites in γ phase. N and S atoms had the preference for octahedral interstitial sites with 6Ni atoms in γ′ phase, while O atom had the preference for octahedral interstitial sites with 2Al4Ni atoms. With the adopted atoms, the intrinsic stacking fault energy in γ phase was decreased and the anti-phase boundary energy in γ′ phase was increased, which were attributed to the charge redistribution between the adopted atoms and neighbouring Ni atoms. The addition of N, S, especially O, hindered the extended dislocation movement and enhanced its formation probability. The addition of O and S atoms significantly enhanced the formation probability of Kear-Wilsdorf dislocation lock in γ′ phase, while the addition of N slightly reduced it.

Exploring the adsorption characteristics of quinoline derivatives on iron via ab initio DFT simulations and COSMO-RS profiles

Quinoline derivatives have been the subject of extensive research due to their excellent electronic properties and wide range of applications. This study conducts a comprehensive computational examination of the adsorption properties of substituted quinoline derivatives on Fe(110) surfaces. Four specific compounds, namely 2-amino-7-hydroxy-4-phenyl-1,4-dihydroquinoline-3-carbonitrile (QN1), 2-amino-7-hydroxy-4-(p-tolyl)-1,4-dihydroquinoline-3-carbonitrile (QN2), 2-amino-7-hydroxy-4-(4-methoxyphenyl)-1,4-dihydroquinoline-3-carbonitrile (QN3), and 2-amino-4-(4-(dimethylamino)phenyl)-7-hydroxy-1,4-dihydroquinoline-3-carbonitrile (QN4) were investigated using first-principles density functional theory (DFT) calculations along with COSMO-RS analysis for solvation properties. Our results revealed that the presence of functional groups significantly influence the adsorption strength on Fe(110) surfaces. Quinoline molecules have adsorbed on the iron surface through complex mechanisms involving physical interactions and charge transfer. Specifically, QN1 and QN4 showed strong physical interactions with iron atoms while QN2 and QN3 exhibited high affinity to coordinate with Fe atoms. The stability of coordinated quinolines was enhanced by a notable charge redistribution and bond formation as observed via projected density of states (PDOS). On the other hand, electron density difference (EDD) and electron localization function (ELF) iso-surfaces highlighted the critical role of van der Waals interactions, predominantly influenced by nitrogen atoms, in stabilizing the adsorbed molecules. The COSMO-RS analysis elucidated the solvation characteristics, emphasizing the importance of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) in the interaction of quinolines with water molecules. Overall, this study provides crucial insights into the molecular mechanisms underlying the corrosion inhibition properties of quinoline derivatives, emphasizing the influence of functional groups and solvation effects on adsorption behavior and stability.

Rapid Detection of Explicit Volatile Organic Compounds for Early Diagnosis of Lung Cancer Using MoSi2N4 Monolayer.

In this study, we investigate the adsorption of MoSi2N4) and MoSi2N4-VNtowards five potential lung cancer volatile organic compounds (VOCs).Density functional theory calculations reveal that MoSi2N4 weakly adsorb the mentioned VOCs, whereas introduction of nitrogen vacancies significantly enhances the adsorption energies ([[EQUATION]]), both in gas phase and aqueous medium. The MoSi2N4-VN monolayers exhibit a reduced bandgap and facilitate charge transfer upon VOCs adsorption, resulting in enhanced [[EQUATION]] values of -0.83, -0.76, -0.49, -0.61, and -0.50 eV for 2,3,4-trimethyl hexane, 4-methyl octane, o-toluidine, Aniline, and Ethylbenzene, respectively. Bader charge analysis and spin-polarized density of states (SPDOS) elucidate the charge redistribution and hybridization between MoSi2N4-VN and the adsorbed VOCs. The work function of MoSi2N4-VN is significantly reduced upon VOCs adsorption due to induced dipole moments, enabling smooth charge transfer and selective VOCs sensing. Notably, MoSi2N4-VN monolayers exhibit sensor responses ranging from 16.2% to 26.6% towards the VOCs, with discernible selectivity. Importantly, the recovery times of the VOCs desorption is minimal, reinforcing the suitability of MoSi2N4-VN as a rapid, and reusable biosensor platform for efficient detection of lung cancer biomarkers. Thermodynamic analysis based on Langmuir adsorption model shows improved adsorption and detection capabilities MoSi2N4-VN under diverse operating conditions of temperatures and pressures.

Tip-like copper sites on high curvature supports for non-covalent to covalent interaction tuning in CO2 photoreduction

Single-atom engineering offers a promising method to transform CO2 into high-value chemicals. The local coordination structure design of the metal-support is crucial for overcoming slow reaction kinetics. In this study, Cu single atoms are immobilized on curved Bi12O17Br2 surface to create a tip-like metal site structure named Cutip-Bi12O17Br2. Due to the high curvature Bi12O17Br2 surface with tensile strain, the tip Cu creates significant electronegativity differences between adjacent Bi atomic sites, creating the vigorous polarization centers. The strong charge redistribution character of tip asymmetric Cu-Bi site favor the polarization of CO bond in nonpolar CO2 and adjust the noncovalent to covalent interaction of reaction intermediates. Benefiting from these features, the optimized Cutip-Bi12O17Br2 enhance the CO production rate by a factor of 34 relative to bulk-Bi12O17Br2, reaching a rate of 96.99 μmol g−1 h−1. This work provides a comprehensive understanding of the structural regulation of single-atom on high curvature surface for CO2 photoreduction.

Observation of a V-Shape Superconductivity Evolution on Tungsten-Intercalated 2H-Type Niobium Diselenide.

van der Waals-layered niobium diselenide (NbSe2) intercalated by d-electron transition metals is an ideal test bed for the exploration of their diversiform evolution of ground states. These intercalations are mostly viewed as ordered structures aligned with periodicities of their host materials that enable control of the electronic phases via gradually changing of intercalation ratios. Here, we present the structure and superconductivity in tungsten (W)-intercalated 2H-NbSe2 crystals, which reveals an order to disorder distribution of W atoms with increasing confined intercalating amounts, leading to an approximate V-shape suppression of superconductivity. Aided by density functional theory calculations, we demonstrate that the local magnetic moment around W intercalants induced by the charge redistribution gives rise to the quick superconductivity suppression in 2H-NbSe2 below a certain dilute amount (W% = 0.06). Simultaneously, W intercalants also induce structural aberration due to aggregation effects and inhibit the generation of an ordered structure in 2H-NbSe2, resulting in a recovery of its superconductivity. The alteration of structure and electronic phases in 2H-NbSe2 via intercalation of nonmagnetic transition metals in the van der Waals gap enables the exploration of combined magnetic quantum criticality, superconductivity, and other related electronic correlations.

Customization of 2D Atomic-Molecular Heterojunction with Manipulatable Charge-Transfer and Band Structure.

Manipulating the properties of 2Dmaterials through meticulously engineered artificial heterojunctions holds great promise for novel device applications. However, existing research on the crucial charge-transfer interactions and energy profile regulation is predominantly focused on 2D van der Waals structures formed via weak van der Waals forces, limiting regulatory efficiency at high costs. Herein, a refined atomic-molecular heterojunction strategy featuring strong covalent bonds between organic molecule and 2D violet phosphorus (VP) atomic crystal is developed, which enables enhanced charge-transfer dynamics and customizable band structure regulation at the molecular level. Both experimentally and theoretically, it is demonstrated that grafting efficiency, charge redistribution, and energy gap regulation critically depend on organic electronegativity, providing a low-cost yet high-efficiency regulatory effect on a large scale. As a proof of concept, the novel VP-molecular heterojunctions exhibit optimized performance in diverse application domains, presenting a general platform for future high-performance device applications.

Crystallographic anisotropy-dependent mechanochemical removal of GaAs: Nanoasperity experiments and atomistic simulations

In this paper, the nanoasperity wear tests on GaAs surfaces with different crystallographic orientations against SiO2 microsphere were performed using AFM. The removal behavior characterized by in-situ AFM imaging significantly relies on crystallographic anisotropy (111 > 110 > 100). The atomic structure of worn area characterized by HRTEM shows perfect crystal lattice, demonstrating the dominate role of the interfacial mechanochemical reactions during the material removal of GaAs. DFT calculations were conducted and the results reveal that the charge re-distribution behavior at the SiO2/GaAs interface governs the mechanochemical reactions, essentially leading to the crystallographic anisotropy dependence. This study not only enriches the mechanochemical reaction mechanism, but also benefits for the CMP optimization for GaAs.

Unraveling the mechanism and the key role of amorphous structure C-O-Fe in tetracycline degradation by activation of persulfate in lotus leaf-based red mud-modified biochar

In the present study, red mud modified lotus leaf biochar was synthesized using a low-cost and concise method. The experimental results showed that when RM-HBC=0.4 g/L, PDS=4 mM, pH=5.0, the RM-HBC-PDS system exhibited the best degradation effect on TC, with the highest removal rate of 98.61 %, the highest degradation kinetics of 0.0229 min−1. Advanced characterization and density functional theory have demonstrated that the emergence of the C-O-Fe structure led to the redistribution of the surface charge of RM-HBC. This charge redistribution caused the electrons on the surface of RM-HBC to transfer from C to Fe through the C-O-Fe structure, forming an electron-rich center centered on Fe. The C-O-Fe structure facilitated the transformation of the Fe valence state within the RM-HBC while transmitting electrons, thus maintaining the regeneration of Fe(II). This further promoted the adsorption and activation ability of RM-HBC for PDS, thereby improving the degradation effect of TC in the system. XRD detection showed that the Fe3O4 crystal strength in RM-HBC after the reaction was significantly enhanced. This was due to the C-O-Fe present on the surface of RM-HBC in the process of degradation of TC, which accelerated sustained electron transfer at C-O-Fe, leading to structural fracture, recombination, and ultimately the formation of Fe3O4 crystals. Intermediate detection and toxicity prediction showed that the toxicity of TC was significantly reduced. All the above results confirmed that this study not only achieved the efficient treatment of antibiotic wastewater but also realized the rational utilization of lotus leaf and red mud resources.

Vinyl-functionalized covalent organic framework via tuning π-conjugation effectively promotes photocatalytic hydrogen evolution

Covalent organic frameworks (COFs) show great potential in photocatalytic water splitting. However, it is still crucial to explore the effect of π-conjugation of COFs on photocatalytic performance. Here, a series of COFs with different degrees of conjugation (DHTA-BD COF, DHTA-STP COF, DHTA-AZO COF) have been investigated through the synergistic effect of varying the planarity and π electronic structures. The results show that the vinyl-functionalized DHTA-STP COF achieves an excellent photocatalytic hydrogen generation rate of 16.1 mmol g1h−1 under visible light conditions, 4.3 times higher than the DHTA-BD COF, and the hydrogen production of the DHTA-AZO COF is extremely low under the same test conditions. Moreover, the synergistic effect of the smaller dihedral angle and ordered π electronic structures with the introduction of vinyl structure in DHTA-STP COF leads to a higher degree of conjugation, facilitating π delocalization efficiency and promoting the redistribution of charges. Experimental and theoretical calculations have demonstrated that DHTA-STP COF is a promising photoactive semiconductor with the strongest photocurrent, the smallest impedance, the narrowest electronic bandgap, and the strongest separation ability of electron-hole pairs. This finding provides guidance for introducing appropriate conjugated units into COFs to improve the photocatalytic hydrogen production efficiency.

Visible-light-driven F/C co-doping g-C3N4 nanosheets for efficient hydrogen evolution: Charge redistribution on C4 delocalized large π bond

Developing photocatalytic hydrogen evolution technology based on graphitic carbon nitride (g-C3N4, CN) has emerged as a potential solution for the future energy shortage in recent years. Herein, carbon (C) and fluorine (F) co-doping graphitic carbon nitride nanosheets (CFCN) were synthesized via a one-pot co-thermal method without introducing any metal element. Exceptional hydrogen production activity (3.87 mmol/h/g) was achieved by CFCN under visible light irradiation, which was 4.2-fold increase compared to the pristine CN. It could be attributed to the large specific surface area (51.59 m2/g) and efficient mass transfer facilitated by the porous sheet-like morphology of CFCN. Additionally, the modification of the band structure and internal charge redistribution were investigated via density functional theory (DFT) calculations, which confirmed there was a unidirectional and fast electron transfer channel from N through the C4 delocalized large π bond to F. This creative research uncovered the pivotal role of F/C co-doping in enhancing photocatalytic hydrogen evolution efficacy, offering cutting-edge insights into the design of sustainable and eco-friendly photocatalysts based on metal-free CN.

DFT insight into the structural, vibrational, and electronic properties of thin [110] Ge nanowires as anodic material for Li batteries

Germanium nanowires could be used to improve as anodic materials since their charge rate is better than that of the current graphite electrodes. In this work, we present a Density Functional Theory study of the effect of interstitial Li atoms on the vibrational, electronic, and mechanical properties of ultrathin hydrogen-passivated Ge nanowires (HGeNWs) with diamond structure, grown along the [110] crystallographic direction, and with a diameter of ∼14.4 Å. The interstitial Li atoms were placed at the tetrahedral positions (Td) reported as the more favorable ones. The phonon band structure of the HGeNWs reveals the existence of high frequency vibrations due to the hydrogen atoms at the nanowire surface. The effect of one interstitial Li atom in the nanowire leads to the apparition of three flat phonon bands almost independent of the collective vibrational states of the nanowire, reflecting a weak interaction between the Li atom and the neighboring ones; and a shift of the high vibrational modes to lower frequencies that results in more dispersive states. The electronic band structure confirms a transition from semiconducting to metallic behavior by adding a single Li interstitial atom per unit cell. The formation energies indicate that the nanowires with interstitial Li atoms are stable, and the average binding energy per Li atom slightly increases as a function of the concentration of Li atoms. The insertion of Li atoms in the nanowire leads to a volumetric expansion, without fracture or broken bonds. Even more, the redistribution of the electronic charge due to the Li atoms give the Ge-Ge bonds more axial elasticity and the values of the modulus of Young are almost constant for all studied concentrations of Li atoms. These theoretical results indicate an improvement of mechanical and electronic properties of Ge nanowires through the addition of interstitial Li atoms that could be important for their use as anodes in rechargeable Li batteries.

Coordination Stabilization of Fe by Porphyrin‐Intercalated NiFe‐LDH Under Industrial‐Level Alkaline Conditions for Long‐Term Electrocatalytic Water Oxidation

AbstractThe durable and economic electrocatalysts with high current density under industrial alkaline conditions are critical for advancing the industrial production of hydrogen energy by water electrolysis. The industrial highly alkaline electrolyte exacerbates the Fe dissolution of NiFe layered double hydroxide (NiFe‐LDH), leading to the dramatic degradation of stability and activity. The NiFe‐LDH intercalated Tetrakis(4‐carboxyphenyl)porphyrin (TCPP) (NiFe‐TCPP), 1,4,7,10‐Tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) (NiFe‐DOTA) and CO32− (NiFe‐CO3) are fabricated respectively for electrocatalytic water oxidation under industrial alkaline conditions. In 10 m KOH, compared to NiFe‐DOTA (335.0 mV) and NiFe‐CO3 (499.2 mV), the resultant NiFe‐TCPP exhibits the lowest overpotentials of 290.2 mV at 1000 mA cm−2. The NiFe‐TCPP also operates continuously for 1000 h at 500 mA cm−2 with near‐zero attenuation. The theoretical and experimental studies reveal that the strong coordination between conjugated carboxylate ligand TCPP and Fe of the laminate inhibits the Fe leaching by increasing the dissolution energy barriers to 4.29 eV and improving the self‐healing ability, thus enhancing the stability. Furthermore, the charge redistribution induced by the strong coordination optimizes the d‐band centers (‐2.81 eV) and decreases the reaction energy barriers (1.47 eV), thereby increasing the catalytic activity.

Constructing hollow cobalt sulfide nanocages strung by manganese molybdate nanorods for high-efficiency supercapacitors and electrocatalytic methanol oxidation

Constructing core-shell heterostuctures with rationally designed nanoarchitectures and components is a promising strategy to pursuit high-efficiency energy storage and conversion in supercapacitors (SCs) and direct methanol fuel cells (DMFCs). Herein, a multi-dimensional MnMoO4@CoS core-shell heterostructure is designed and synthesized by stringing metal-organic framework-derived hollow CoS nanocages with MnMoO4 nanorods. Such heterostructure provides more electroactive sites and enhanced structural stability. Theory calculations unveil that the work function difference between MnMoO4 and CoS induces the charge redistribution and modulate interfacial electronic configuration in the MnMoO4/CoS heterojunction. Meanwhile, a interfacial built-in electrical field is established, enhancing interfacial charge transfer efficiency and promoting the surface adsorption of electrolyte ions. By integrating all these advantages, the MnMoO4@CoS electrode demonstrates enhanced rate capacities (933 C g−1 at 1 A g−1 and 623 C g−1 at 10 A g−1) and cycling durability (90.3 % capacity retention after 10,000 cycles) compared to bare MnMoO4 and CoS electrodes. Moreover, the MnMoO4@CoS electrode exhibits an appreciable electrocatalytic performance for methanol oxidation, with a current density of 294.8 mA cm−2 at 10 mV s−1 and 96.6 % current retention after 10,000 s. Our work offers a fundamental guideline for designing and engineering core-shell heterostructures with desirable electrochemical performance for SCs and DMFCs.