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Heteroatom doping, especially with elements of lower electronegativity and smaller atomic radius, can effectively modulate the electronic structure and surface properties of electron materials, facilitating the electrochemical performance of supercapacitors. Herein, we have designed boron-doped NiCoP nanoarrays grown on carbon cloth (B-NCP-CC) for supercapacitor cathode materials using a simple process method combining hydrothermal, calcined phosphating and boronation processes. The introduction of boron, with lower electronegativity (2.04) and smaller atomic radius (0.85 Å) than phosphorus (2.19 and 1.00 Å), induces electron redistribution and shortens the Ni/Co–B bonds, enhancing their redox activity and charge transfer kinetics. The boron doping greatly enables the B-NiCoP-CC-18 (NiCoP-CC borated for 18 h) cathode material to provide a high capacity of 801 C g−1. The assembled B-NiCoP-CC-18‖‖AC hybrid supercapacitor achieves a high energy density of 73.22 W h kg−1 at a power density of 963.8 W kg−1 and retains 90% capacity after 5000 cycles, significantly improving the stability of nickel-based materials. Besides, density functional theory (DFT) calculations further elucidate that the introduction of boron increases the d-band centers of Ni and Co in NiCoP, promoting the conductivity and enhancing the electrochemical properties. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWCNTs) functionalized with sparse surface chemical groups are promising for a variety of optical applications such as quantum information and bio-imaging. However, the luminescence efficiencies and stability, two key aspects, undoubtedly govern their practical usage. Herein, we assess the surface migration of oxygen and triazine groups on as-modified SWCNT fragments by adopting transition state theory and explore the de-excitation of oxygen-functionalized SWCNT fragments by performing non-adiabatic excited-state dynamics simulations. According to the predicted moderate or even small reaction barriers, the migration of both oxygen and triazine groups is feasible from an sp3 defect configuration forming an energetically more stable sp2 configuration at moderate or even room temperatures. Such isomerization leads to drastically different light emission capabilities as indicated by the large or zero oscillator strengths. During the dynamics simulations, the lowest excited singlet (S1) state rapidly decays in energy within 20 fs and then fluctuates until the end, providing insights into the emission mechanism of SWCNTs. This study highlights the potential intrinsic limitations of surface-functionalized SWCNTs for luminescence applications. [ABSTRACT FROM AUTHOR]

Liquid–liquid phase transition (LLPT) is a transition from one liquid state to another with the same composition but distinct structural change, which provides an opportunity to explore the relationships between structural transformation and thermodynamic/kinetic anomalies. Herein the abnormal endothermic LLPT in Pd43Ni20Cu27P10 glass-forming liquid was verified and studied by flash differential scanning calorimetry (FDSC) and ab initio molecular dynamics (AIMD) simulations. The results show that the change of the atomic local structure of the atoms around the Cu-P bond leads to the change in the number of specific clusters <0 2 8 0> and <1 2 5 3>, which leads to the change in the liquid structure. Our findings reveal the structural mechanisms that induce unusual heat-trapping phenomena in liquids and advance the understanding of LLPT. [ABSTRACT FROM AUTHOR]

Electrocatalytic O2 conversion and water-splitting hold great promise to enable the chemicals–electricity inter-transition in many renewable-energy initiatives. Enhancing the kinetics of the oxygen reduction reaction (ORR) is challenging. Here, we present that Zn3(VO4)2/Ni(OH)2/rGO (reduced graphene oxide) nanosheet arrays-a Zn3(VO4)2/Ni(OH)2 composite in the form of nanometre-thick nanosheets on an rGO substrate-serve as an efficient and stable electrocatalyst for the ORR in alkaline electrolytes. The thin-sheet structure and smaller free energy of Zn3(VO4)2/Ni(OH)2, as well as the excellent conductivity of the rGO substrate, enable a large electrochemically-active surface area and a high electron transport, contributing to the superior electrocatalytic oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Furthermore, Zn3(VO4)2/Ni(OH)2/rGO and Zn3(VO4)2/Ni(OH)2 samples exhibit remarkable long-term water-splitting stability of 48 h. Density functional theory (DFT) calculations reveal the optimized intermediate affinity ability at the Ni(OH)2 side, due to electrons transferring from Ni(OH)2 to Zn3(VO4)2. Additionally, the higher hybridization degree of density of states (DOS) boosts electron transfer in the electrocatalytic process. More broadly, this work provides new inspiration for the construction of a novel noble metal-free electrocatalyst that could show great promise in energy electrocatalysis. [ABSTRACT FROM AUTHOR]

Hydrogen is considered a promising clean energy vector with the features of high energy capacity and zero-carbon emission. Water splitting is an environment-friendly and effective route for producing high-purity hydrogen, which contains two important half-cell reactions, namely, the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER). At the heart of water splitting is high-performance electrocatalysts that efficiently improve the rate and selectivity of key chemical reactions. Recently, perovskite oxides have emerged as promising candidates for efficient water splitting electrocatalysts owing to their low cost, high electrochemical stability, and compositional and structural flexibility allowing for the achievement of high intrinsic electrocatalytic activity. In this review, we summarize the present research progress in the design, development, and application of perovskite oxides for electrocatalytic water splitting. The emphasis is on the innovative synthesis strategies and a deeper understanding of structure–activity relationships through a combination of systematic characterization and theoretical research. Finally, the main challenges and prospects for the further development of more efficient electrocatalysts based on perovskite oxides are proposed. It is expected to give guidance for the development of novel non-noble metal catalysts in electrochemical water splitting. [ABSTRACT FROM AUTHOR]

Electrode materials exhibiting higher structural stability and electrochemical activity remain a priority in improving the electrochemical performance of supercapacitors (SCs). Herein, we report the design and synthesis of a novel nanoplate-on-nanosheet architecture with vertically aligned ZnCo2O4 (ZCO) porous nanoplates anchored on ultrathin delaminated-Ti3C2 (d-TC) nanosheets as a high-performance electrode for electrochemical SCs. The unique robust nanoplate-on-nanosheet adhesion promises fast electron and ion transport, large electroactive surface area, and excellent structural stability. Importantly, benefiting from the features of such a configuration, the ZCO/d-TC-350 composite electrode displays a high specific capacity of 195.8 C g−1 at a current density of 1 A g−1. Moreover, the constructed hybrid supercapacitor (HSC) consisting of ZCO/d-TC-350‖‖active carbon (AC) achieves a high energy density of 15.6 W h kg−1 at a power density of 551.1 W kg−1 and superior long-term stability with 89.5% capacitance retention after 4000 cycles. This work provides a promising strategy for the preparation of advanced MXene-based electrodes for electrochemical capacitors. [ABSTRACT FROM AUTHOR]

Coralloid-Pt nanodendrites decorated nanoporous gold films (NPG-Ptx) were fabricated through underpotential deposition/in-situ reduction replacement (UPD/IRR) strategy and exhibit significantly enhanced ORR activities. Ab initio density functional theory (DFT) studies further demonstrate the ORR mechanism of NPG-Ptx. [Display omitted] • Coralloid-Pt nanodendrites decorated nanoporous gold films (NPG-Ptx) were fabricated through underpotential deposition/in-situ reduction replacement (UPD/IRR) strategy. • The NPG-Ptx (x = 1 ∼ 4) exhibit significantly enhanced ORR activities in acidic media. • The DFT studies demonstrate the ORR mechanism and rate-determining step of NPG-Ptx follow the free energy diagrams. • The PDOS results indicate a relatively stronger O 2 reaction capacity on Pt side than Pt top. Deposition of trace amounts of Pt onto nanoporous gold ligaments (NPG-Pt) has demonstrated promising performance of low-Pt electrocatalysts for oxygen reduction reaction (ORR); however, improving the activity of ORR remains challenging because of the difficulty in understanding the electronic effect between Pt and NPG as well as the absence of ORR mechanism studies on NPG-Pt. Here we show that NPG-Ptx (x = 1 ∼ 4), unique coralloid-Pt nanodendrites decorated nanoporous gold films through underpotential deposition/in-situ reduction replacement (UPD/IRR) strategy, exhibit significantly enhanced ORR activities. Among them, NPG-Pt3 exhibits the best ORR activity compared with the others and Pt/C in acidic media. Density functional theory (DFT) studies demonstrate the ORR mechanism and rate-determining step of NPG-Ptx follow the free energy diagrams. Furthermore, the projected density of state (PDOS) results reveal a relatively weaker O 2 reaction capacity on the top side of Pt (Pt top) than the side site (Pt side) for NPG-Ptx. The increase of d -band center for NPG-Ptx pushes up the energy of the antibonding state above the Fermi level, and then the backflow of electrons into the system makes the energy more stable, optimizing the ORR activity. These results provide new inspirations for the development of low-Pt electrocatalysts for energy technologies in a rational manner. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical NiC 2 O 4 /Ni(OH) 2 nanospheres are synthesized via a simple two-step hydrothermal method as the positive electrode. • The porous biomass-derived carbon with the honeycomb structure is obtained from pine petals as the negative electrode. • Hierarchical NiC 2 O 4 /Ni(OH) 2 nanospheres and the porous biomass-derived carbon possess a high specific capacity. • The hybrid supercapacitor exhibits excellent energy and power density. The high-performance hybrid supercapacitor (HSC) with high power capability and stable cyclability is intensively pursued as a next-generation energy storage device. Here, a kind of hierarchical NiC 2 O 4 /Ni(OH) 2 nanospheres, consisting of subunits of NiC 2 O 4 nanorods and Ni(OH) 2 nanospheres, are synthesized via a two-step hydrothermal method. The hierarchical NiC 2 O 4 /Ni(OH) 2 nanosphere positive electrode, benefiting from the synergistic effect of unique hierarchical structure and built-in electric fields, significantly boosting electron transmission capability and accelerating the ion/electron transfer rate, delivers an excellent specific capacity of 668 C g−1 at 1 A g−1. In addition, the porous biomass-derived carbon (PBC) with the honeycomb structure from pine petals as the negative electrode shows a remarkable electrochemical performance, exhibiting a specific capacitance of 249.7 F g−1 at 1 A g−1. As such, an assembled HSC of NiC 2 O 4 /Ni(OH) 2 ||PBC based on hierarchical NiC 2 O 4 /Ni(OH) 2 nanospheres positive electrode and PBC negative electrode display a conspicuous energy density of 31.07 Wh kg−1, and a power density of 833.47 W kg−1 at a maximum potential window of 1.7 V. This innovative hierarchical engineering of double nickel-based composites with bio-carbon provides an advanced enlightenment for high-performance HSCs. [ABSTRACT FROM AUTHOR]

Efficient and robust non-platinum-group metal electrocatalysts for O 2 reduction are a prerequisite for practical high-performance fuel cells and metal-air batteries. Herein, we reported an integrated principle of gradient electrospinning and controllable pyrolysis to fabricate various Co-doped Ni 3 V 2 O 8 nanofibers with high oxygen reduction reaction (ORR) activity. The representative Co 1.3 Ni 1.7 V 2 O 8 nanofibers showed outstanding ORR performance in an alkaline solution with a half-wave potential ( E 1/2 ) of 0.874 V vs RHE, along with high long-term stability. Furthermore, the introduction of Co could effectively restrain the growth of nanoparticles and change the electronic structure of Ni 3 V 2 O 8 . Control experiments and theoretical calculations demonstrated that upon Co-doping, the hybridization between the 3d orbital for both Co and Ni guaranteed the stable adsorption interaction with O 2 over Ni and Co metal centers. Meanwhile, the weakened binding ability of Ni 3 V 2 O 8 to OH* reduced the ORR free energy. Overall, the synergistic effect of Co and Ni metal cations essentially reflected the origin of ORR activity on the Co-doped Ni 3 V 2 O 8 nanofibers. This work offers new insights and practical guidance for designing highly active ORR catalysts for electrochemical clean energy conversion and storage.