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Potassium-ion batteries (PIBs) have attracted enormous attention due to the increasing lithium battery cost, but their development is still in the pre-mature stage due to the limited selection of electrodes. Herein, a free-standing current-collector-integrated electrode, composed of mixed-phase WS

The morphology and size of Pt-based bimetallic alloys are known to determine their electrocatalytic performance in reactions relevant to fuel cells. Here, we report a general approach for preparing Pt-M (M = Fe, Co and Ni) bimetallic nano-branched structure (NBs) by a simple high temperature solution-phase synthesis. As-prepared Pt-M NBs show a polycrystalline structure and are rich in steps and kinks on the surface, which promote them favorable bifunctional catalytic properties in acidic electrolytes, specifically in terms of the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). Specially, Pt-Co NBs/C catalyst shows 6.1 and 5.3 times higher in specific activity (SA) and mass activity (MA) for ORR than state-of-the-art commercial Pt/C catalysts, respectively. Moreover, it exhibits a loss of 4.0% in SA and 14.4% in MA after 10,000 cycles of accelerated durability tests (ADTs) compared with the initial activities. In addition, we also confirmed the superior MOR activity of Pt-Co NBs/C catalyst in acidic electrolytes. For Pt-M NBs with other alloying metals, the ORR and MOR activities are both higher than commercial catalysts and are in the sequence of Pt-Co/C > Pt-Fe/C > Pt-Ni/C > commercial Pt/C (or PtRu/C). The improved activities and durability can benefit from the morphological and compositional effects. This synthesis approach may be applied to develop bifunctional catalysts with enhanced ORR and MOR properties for future fuel cells designs.

Tin selenides have been attracting great attention as anode materials for the state-of-the-art rechargeable sodium-ion batteries (SIBs) due to their high theoretical capacity and low cost. However, they deliver unsatisfactory performance in practice, owing to their intrinsically low conductivity, sluggish kinetics and volume expansion during the charge-discharge process. Herein, we demonstrate the synthesis of SnSe2 nanocrystals coupled with hierarchical porous carbon (SnSe2 NCs/C) microspheres for boosting SIBs in terms of capacity, rate ability and durability. The unique structure of SnSe2 NCs/C possesses several advantages, including inhibiting the agglomeration of SnSe2 nanoparticles, relieving the volume expansion, accelerating the diffusion kinetics of electrons/ions, enhancing the contact area between the electrode and electrolyte and improving the structural stability of the composite. As a result, the as-obtained SnSe2 NCs/C microspheres show a high reversible capacity (565 mA h g−1 after 100 cycles at 100 mA g−1), excellent rate capability, and long cycling life stability (363 mA h g−1 at 1 A g−1 after 1000 cycles), which represent the best performances among the reported SIBs based on SnSe2-based anode materials.

Sodium-ion (Na-ion) hybrid capacitors as a novel electrochemical energy storage device have triggered considerable attention in recent years. However, the sluggish kinetics at anode and low specific capacity at cathode greatly hinder the overall performance output of Na-ion hybrid capacitors. Herein, we design a high-performance quasi-solid-state Na-ion hybrid capacitor assembled with the Mo2N quantum dots coupled carbon nanotubes as anode, decoupled hierarchical carbon nanotubes as cathode, and a porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane based gel electrolyte. For the anode, the uniformly dispersed Mo2N quantum dots offer abundant ion-accessible active sites and shortened ion diffusion path, which effectively accelerate Na ion storage kinetics. After decoupling and activation, the hierarchical carbon nanotubes with high specific surface area and numerous in-plane nanopores contribute to fast reversible anion adsorption and desorption, greatly boosting the specific capacity. Additionally, the low-tortuosity nanotubular electrode microstructure with open framework is conducive to unimpeded electrolyte ion permeation and thereby can maximize the utilization of active materials. Benefiting from the elaborate electrode architecture engineering and rational device configuration, the assembled quasi-solid-state Na-ion hybrid capacitor can achieve a high energy density of 100.6 Wh kg−1 at a power density of 117.5 W kg−1, which is among the best compared with other Na-ion hybrid capacitors. The demonstration of proof-of-concept of the quasi-solid-state Na-ion hybrid capacitors offers new insights into rational design of high-energy-density hybrid energy storage systems.

Developing efficient water-splitting electrocatalysts with high mass activity is in urgent need for large-scale sustainable production of hydrogen but, still remains as a big challenge. Herein, we report a one-pot method to fabricate a series of core@shell Ni@RuM (M=Ni or Co) nanocrystals (NCs) with Ni as the core and tunable RuM (M=Ni or Co) as the alloy shell for efficient water-splitting catalysis. Among these core@shell NCs, the obtained Ni@RuNi NCs exhibit the highest intrinsic activity for hydrogen evolution reaction (HER) and possess an outstanding mass activity of 1590 mA mgRu−1 at 0.07 V vs. reversible hydrogen electrode (RHE), which is 1.7 times higher than that of commercial Pt/C ( 950 mA mgPt−1 ). As for oxygen evolution reaction (OER), the prepared Ni@Ru0.4Co0.6 NCs with optimized shell composition achieve more enhanced mass activity of 270 mA mgRu−1 at 1.56 V vs. RHE, approaching three times higher than that of commercial RuO2 ( 89 mA mgRu−1 ). The superb mass activity of these Ni@RuM (M=Ni or Co) NCs can be attributed to their core@shell structure and modulated electronic structure through alloying with Ni or Co metal in the shell.

Tuning reactive metal-support interaction (RMSI) is a promising approach to optimizing catalytic active sites via the electronic, geometric and compositional effects. In general, the RMSI is conducted on the reducible oxides via a high-temperature reaction (>550 °C). Herein we report a strong RMSI between Pt single atom (PtSA) and non-oxide-based g-C3N4 built by an in-situ photocatalytic reduction method at a sub-zero temperature. The experimental observation confirms that the rich N vacancies in g-C3N4 produce an obvious electron-deficient effect, which greatly enhances the RMSI. This strong RMSI contributes to the highest PtSA coverage density of 0.35 mg m−2 reported to date in carbon-based materials and outstanding H2-evolution activity of 174.5 mmol g−1 h−1 per PtSA relative to those on the electron-rich g-C3N4. The structure simulation reveals that the RMSI can not only stabilize the PtSA on the electron-deficient g-C3N4 via the strong chemical bond between PtSA and the two-coordinated C (C2C) sites caused by the N vacancies, but also promises the PtSA with an optimized electronic and geometric structures for capturing photogenerated electrons and producing H2. This finding opens a new channel for designing and manipulating single atom-loaded photocatalyst via the RMSI at a sub-zero low temperature.

Sub-nanometer noble metal catalysts, especially single atom (SA), are a new class of catalytic materials for boosting catalysis and possess unique catalytic properties and high atomic utilization efficiency. Exploring the interaction between two neighboring atom monomers has great potential to further improve the performance of SA catalysts and deepen the understanding on the catalytic mechanism of heterogeneous catalysis at the atomic level. Herein, we demonstrate that the synergetic effect between neighboring Pt and Ru monomers supported on N vacancy-rich g-C3N4 promotes the catalytic CO oxidation. The experimental observation and theoretical simulation reveal that the N vacancy in the g-C3N4 structure builds an optimized triangular sub-nanometer cavity for stabilizing the neighboring Pt–Ru monomers by forming Pt–C and Ru–N bonds. The mechanistic studies based on the in situ IR spectrum and theoretical simulation confirm that the neighboring Pt–Ru monomers possess a higher performance for optimizing O2 activation than Ru–Ru/Pt–Pt monomers or isolated Ru/Pt atoms by balancing the energy evolution of reaction steps in the catalytic CO oxidation. The discovery of the synergetic effect between neighboring monomers may create a new path for manipulating the catalytic properties of SA catalysts.

The dehydrogenation and conversion of methanol into 1,1-dimethoxymethane (DMM) was achieved over noble metal-free photocatalyst CdS/Ni2P under visible light. This photocatalytic process for methanol-to-H2 and DMM conversion is efficient and atom economic, with an optimal rate and selectivity of DMM of 188.42 mmol g−1 h−1 and 82.93%, respectively. This work supplies a new green approach for the direct efficient conversion of methanol into DMM and provides a promising avenue for sustainable bio-methanol applications.

Excavating and developing highly efficient and cost-effective nonnoble metal single-atom catalysts for electrocatalytic reactions is of paramount significance but still in its infancy. Herein, reported is a general NaCl template-assisted strategy for rationally designing and preparing a series of isolated transition metal single atoms (Fe/Co/Ni) anchored on honeycomb-like nitrogen-doped carbon matrix (M1 -HNC-T1 -T2 , M = Fe/Co/Ni, T1 = 500 °C, T2 = 850 °C). The resulting M1 -HNC-500-850 with M-N4 active sites exhibits superior capability for oxygen reduction reaction (ORR) with the half-wave potential order of Fe1 -HNC-500-850 > Co1 -HNC-500-850 > Ni1 -HNC-500-850, in which Fe1 -HNC-500-850 shows better performance than commercial Pt/C. Density functional theory calculations reveal a choice strategy that the strong p-d-coupled spatial charge separation results the Fe-N4 effectively merges active electrons for elevating d-band activity in a van-Hove singularity like character. This essentially generalizes an optimal electronic exchange-and-transfer (ExT) capability for boosting sluggish alkaline ORR activity. This work not only presents a universal strategy for preparing single-atom electrocatalyst to accelerate the kinetics of cathodic ORR but also provides an insight into the relationship between the electronic structure and the electrocatalytical activity.

Efficient charge separation and sufficiently exposed active sites are important for light-driving Fenton catalysts. 0D/2D hybrids, especially quantum dots (QDs)/nanosheets (NSs), offer a better opportunity for improving photo-Fenton activity due to their high charge mobility and more catalytic sites, which is highly desirable but remains a great challenge. Herein, a 0D hematite quantum dots/2D ultrathin g-C3 N4 nanosheets hybrid (Fe2 O3 QDs/g-C3 N4 NS) is developed via a facile chemical reaction and subsequent low-temperature calcination. As expected, the specially designed 0D/2D structure shows remarkable catalytic performance toward the removal of p-nitrophenol. By virtue of large surface area, adequate active sites, and strong interfacial coupling, the 0D Fe2 O3 QDs/2D g-C3 N4 nanosheets establish efficient charge transport paths by local in-plane carbon species, expediting the separation and transfer of electron/hole pairs. Simultaneously, highly efficient charge mobility can lead to continuous and fast Fe(III)/Fe(II) conversion, promoting a cooperative effect between the photocatalysis and chemical activation of H2 O2 . The developed carbon-intercalated 0D/2D hybrid provides a new insight in developing heterogeneous catalysis for a large variety of photoelectronic applications, not limited in photo-Fenton catalysis.

Despite its very high capacity (4200 mAh g–1), the widespread application of the silicon anode is still hampered by severe volume changes (up to 300%) during cycling, which results in electrical contact loss and thus dramatic capacity fading with poor cycle life. To address this challenge, 3D advanced Mxene/Si-based superstructures including MXene matrix, silicon, SiOx layer, and nitrogen-doped carbon (MXene/Si@SiOx@C) in a layer-by-layer manner were rationally designed and fabricated for boosting lithium-ion batteries (LIBs). The MXene/Si@SiOx@C anode takes the advantages of high Li+ ion capacity offered by Si, mechanical stability by the synergistic effect of SiOx, MXene, and N-doped carbon coating, and excellent structural stability by forming a strong Ti–N bond among the layers. Such an interesting superstructure boosts the lithium storage performance (390 mAh g–1 with 99.9% Coulombic efficiency and 76.4% capacity retention after 1000 cycles at 10 C) and effectively suppresses electrode swelling only ...

Despite its very high capacity (4200 mAh g

Potassium-ion batteries (PIBs) have attracted enormous attention due to the increasing lithium battery cost, but their development is still in the pre-mature stage due to the limited selection of electrodes. Herein, a free-standing current-collector-integrated electrode, composed of mixed-phase WS2 nanosheets with nitrogen-doped multichannel carbon nanofibers (N-MCNFs) membrane, is reported for high-performance potassium ion batteries anode. Benefiting the unique multichannel carbon nanos-tructure as a current collector-integrated electrode as well as mixed-phase lamellar structure WS2 for enhanced potassium ion entry, the 1T/2H-WS2/N-MCNFs hybrid current-collector-free anode delivers an outstanding areal capacity of 2.88 mAh cm-2 (corresponding to 411 mAh/g based on the mass of both electrode and current collector) at a current of 0.7 mA cm-2 as well as long-term cycling stability for over 1000 cycles at a high current of 14 mA cm-2, surpassing the current state-of-art PIB anode. It is believed that our findings based on the high energy current collector integrated electrode at high mass loading would boost future research on practical metal ion batteries.(c) 2022 Elsevier Inc. All rights reserved.