Phosphorus Vacancies Induced Electron Redistribution of Ni-CoP1-x/Ti3C2 Boosting Bimetallic Redox Activity for High-Performance Hybrid Supercapacitors.

Aqueous zinc-ion batteries (AZIBs) are promising candidates for large-scale grid energy storage due to their inherent safety, durability, and low cost. However, their practical performance is hampered by the hydrogen evolution reaction (HER) on the Zn anode, which causes unstable Zn/electrolyte interfacial pH values, resulting in the formation of byproducts and uncontrollable Zn dendrite growth. To address these issues, we developed a layered solid Brønsted acid HNbMoO6·H2O (HNM) for interfacial pH regulation and Zn anode protection. Density functional theory (DFT) calculations suggested that the strong adsorption of OH- ions by HNM (Eads = -4.15 eV) and the presence of abundant interlayer hydrated protons in HNM facilitated effective adsorption and neutralization of OH- ions, thereby offering stable interfacial pH values, preventing alkaline byproduct formation and suppressing tip-induced dendrite growth. Moreover, the layered HNM established stable ion transport channels, enabling ordered Zn2+ flux and homogeneous Zn2+ deposition. Notably, HNM simultaneously inhibited the HER and accelerated the Zn2+/Zn plating/stripping kinetics. Consequently, HNM@Zn enabled an excellent Coulombic efficiency of 99.7% (over 1000 cycles) in asymmetrical cells, an exceptional Zn2+ transference number of 0.79 and stable cycling for over 1750 hours in symmetrical cells, retaining a capacity of 130 mAh g-1 after 1000 cycles in HNM@Zn||α-MnO2 full cells. This work provides insights into multifunctional anode engineering for interfacial pH regulation towards high-performance AZIBs.

Developing cost‐effective and highly efficient oxygen evolution reaction (OER) electrocatalysts that operate in both acidic and alkaline media is crucial for industrial electrocatalytic water splitting. However, achieving high performance under dual pH conditions remains a significant challenge. Herein, we report the synthesis of multi‐sized RuO2 sub‐nanoclusters on Co3O4 nanoarrays via a facile method, which demonstrates exceptional OER activity in both acidic and alkaline environments. The optimized catalyst exhibits remarkably low overpotentials of 165 mV in 0.5 M H2SO4 and 223 mV in 1 M KOH at a current density of 10 mA cm−2, respectively. Additionally, it exhibits outstanding stability, maintaining performance over a 10‐h continuous operation, which is attributed to the robust structural stability of the dispersed RuO2 sub‐nanocluster morphology. Atomic‐scale investigations reveal a layer‐by‐layer growth mechanism of Ru on the Co3O4 substrate, transitioning from single atoms to monolayer clusters and ultimately to sub‐nanoclusters as Ru loading increases. This growth mechanism provides a rational strategy for the precise design and synthesis of advanced cluster‐based catalysts. Density functional theory (DFT) calculations further elucidate the strong oxide‐support interactions between RuO2 clusters and the Co3O4 matrix, facilitating electron transfer from RuO2 to Co3O4 and generating an electron‐deficient region. This electronic modulation enhances –OH adsorption and accelerates OER kinetics. These findings underscore the potential of metal sub‐nanoclusters for designing highly efficient and durable electrocatalysts for water electrolysis.image

Interface engineered hydrangea-like ZnCo2O4/NiCoGa-layered double hydroxide@polypyrrole core-shell heterostructure for high-performance hybrid supercapacitor

Carbon aqueous symmetric supercapacitors are attractive supercapacitor devices owing to the low-cost and high conductivity of porous carbons. However, the limited capacitive charge storage process in carbon symmetric capacitors still leads to low energy density even when the cell voltage is extended up to 2.0 V in neutral aqueous electrolytes. Meanwhile, a carbon/metal ion capacitor such as sodium (Na), lithium (Li), Potassium (K) and much recently, zinc (Zn) can easily achieve high energy density from the synergistic contribution of double layer and mono/multivalent faradaic charge storage. Taking Zn-based devices as an example, the zinc anode presents the advantages of the large theoretical capacity of Zn, low redox potential, excellent stability and lower cost in comparison with Na and Li. The major emphasis on Zn-ion hybrid supercapacitor research has been on the energy density. However, compared with a carbon symmetric supercapacitor, the zinc stripping/de-stripping reaction occurring at the zinc may increase the overall equivalent series resistance leading to lower gravimetric power density. Since the study of these devices is still in its infancy, it is highly necessary to devise an effective strategy to enhance the gravimetric power density as well. Herein, we successfully report a recoverable activated zinc ion hybrid supercapacitor with enhanced high rate charge storage, improved rate capability and gravimetric power density by utilizing a mixed mono/multivalent electrolyte. A facilely activated carbon fiber clothes with a large specific surface area (615 m2 g-1), rich microporosity and superhydrophilicity serves as the positive electrode, whiles zinc foil serves as anode. At first, a zinc-ion HSC is fabricated using conventional 1 M ZnSO4 electrolyte, and the device exhibits a high voltage drop of 1.21 V at 50 mA cm-2, which would definitely affect the rate capability and maximum gravimetric power density of the device. This voltage drop is almost halved to 0.68 V at 50 mA cm-2 as well as the equivalent series resistance is significantly reduced, using the mono/multivalent aqueous electrolyte. This translates into charge storage at the high current density of 50 mA cm-2, a rate capability of 55 % compared to 38 % in the conventional ZnSO4 electrolyte and a maximum gravimetric energy density of 130.2 kW kg-1, compared to 73.62 kW kg-1 in the conventional ZnSO4 electrolyte. Using ex-situ SEM, XRD and cyclic voltammetry characterizations, we fully confirm that the 1 M Na2SO4 inhibits the formation of ZnO/Zn4SO4(OH)6•5H2O dendrites and serves as the preferential adsorption electrolyte at high rates in the carbon positive electrode. In terms of energy density, the fabricated Zn-ion HSC achieves a maximum energy density of 81.4 Wh kg-1, far exceeding fabricated carbon symmetric capacitors as well as stable cycling performances up to 10000 cycles with ~ 99 % coulombic efficiencies. Finally, we believe our work will draw research attention into developing high-energy, high-rate and high-power aqueous Zn-ion supercapacitors through electrolyte modification.

Electrocatalytic activity of the oxygen reduction reaction (ORR) on carbon-supported metallophthalocyanine (MPc/C, M = Fe, Co, Ni, and Mn) catalysts was studied with a rotating disk electrode (RDE) and a rotating ring-disk electrode (RRDE) in 0.1 M NaOH solutions. FePc/C shows better ORR activity than CoPc, NiPc, and MnPc in 0.1 M NaOH solutions. Density functional theory (DFT) calculations were performed to study the adsorption of O2, H2O, OH, HOOH, and H2OO molecules on FePc, CoPc, NiPc, and MnPc molecule catalysts. Investigations using various MPc/C molecules as the cathode catalyst in anion exchange membrane fuel cells (AEMFCs) revealed that the catalysts, such as FePc/C, with high ORR activities observed with a RDE in 0.1 M NaOH solutions, do not warrant the high performance observed in the AEMFCs. DFT calculation results indicate that the FePc molecules are favorable for the adsorption of OH− rather than O2 or H2O, especially under AEMFC operation conditions. Electrochemical impedance (EIS) spectra obtained while operating the AEMFCs revealed that the resistance of OH− transportation from the cathode to the anode depends on the cell potentials and the nature of the MPc molecules. As predicted by the DFT calculation results, the FePc/C catalyst shows the highest OH− transport resistant at a high current and a low cell voltage region. The bonding strength between OH− and MPc molecules is a critical factor that determines the performance of the MPc molecules in AEMFCs. The fundamental discrepancy between ORR activities observed with an RDE in a standard three-electrode cell and ORR activities observed in an AEMFC is discussed.

Multistage interface engineered cobalt polysulfides core-shell nanostructures for dual energy storage devices and hydrogen evolution

Efficient Life-Cycle Management: Recyclable self-support MnCuOxS1-x wastewater treatment catalyst for electrosynthesis of benzoic acid to accelerate hydrogen production

Study of O 2 and OH adsorption energies on Pd–Cu alloys surface with a quantum chemistry approach

Improved rate capability and energy density of high-mass hybrid supercapacitor realized through long-term cycling stability testing and selective electrode design

Iron-doped nickel–cobalt bimetallic phosphide nanowire hybrids for solid-state supercapacitors with excellent electromagnetic interference shielding

Synergistic interface engineering of ZnCo2O4/NiMnCo-layered double hydroxides for boosted reactivity in advanced supercapacitor electrodes

Modulating charge distribution of MIL@CuFe-Se by in-situ interface engineering for high performance supercapacitors

Lithium–sulfur batteries have aroused great interest in the context of rechargeable batteries, while the shuttle effect and sluggish conversion kinetics severely handicap their development. Defect engineering, which can adjust the electronic structures of electrocatalyst, and thus affect the surface adsorption and catalytic process, has been recognized as a good strategy to solve the above problems. However, research on phosphorus vacancies has been rarely reported, and how phosphorus vacancies affect battery performance remains unclear. Herein, CoP with phosphorus vacancies (CoP‐Vp) is fabricated to study the enhancement mechanism of phosphorus vacancies in Li–S chemistry. The derived CoP‐Vp features a low Co‐P coordination number and the introduced phosphorus vacancies mainly exist in the form of clusters. The obtained CoP‐Vp can reinforce the affinity to lithium polysulfides (LiPSs) and thus the shuttle effect can be restrained. In addition, the reduced reaction energy barriers and the promoted diffusion of Li+ can accelerate redox kinetics. Electrochemical tests and in situ Raman results confirm the advantages of phosphorus vacancies. The S/CNT‐CoP‐Vp electrode presents outstanding cycling performance and achieves a high capacity of 8.03 mAh cm−2 under lean electrolyte condition (E/S = 5 μLE mg−1S). This work provides a new insight into improving the performance of Li–S batteries through defect engineering.

Solid materials with special atomic and electronic structures are deemed desirable platforms for establishing clear relationships between surface/interface structure characteristics and electrochemical activity. In this work, nickel boride (NixB) and nickel boride/graphene (NixB/G) are chosen as positive materials of supercapacitors. The NixB/G displays higher specific capacitance (1822 F g-1) than that of NixB (1334 F g-1) at 1 A g-1, and it still maintains 1179 F g-1 at 20 A g-1, suggesting the high rate performance. The asymmetric supercapacitor device (NixB/G//activated carbon) also delivered a very high energy density of 50.4 Wh kg-1, and the excellent electrochemical performance is ascribed to the synergistic effect of NixB, Ni(BO2)2, and graphene that fully enhances the diffusion of OH- and the electron transport. During the cycles, the prepared ultrafine NixB nanoparticles will be gradually in situ converted into β-Ni(OH)2 which has a smaller particle size than that prepared by other methods. This will enhance the utilization of Ni(OH)2 and decrease the ion diffusion distance. The electron deficient state of B in Ni(BO2)2 amorphous shell will make it easy to accept extra electrons, enhancing the adsorption of OH- at the shell surface. Moreover, Ni(BO2)2 makes strong adhesion between NixB (or β-Ni(OH)2) and graphene and protects the core structure in a stable state, extending the cycle life. The above properties of NixB/G endow the electrode good capacitive performance.

Influence of ∗OH adsorbates on the potentiodynamics of the CO2 generation during the electro-oxidation of ethanol