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The layered LiCoO2 cathode plays a key role in high-energy-density lithium-ion batteries (LIBs), delivering a capacity of ∼185 mA h g−1 at a high cut-off voltage of 4.5 V (vs. Li/Li+). However, its practical applications in high-voltage LIBs are limited by a severe side reaction and an irreversible structure transition during cycling. Herein, we report a facile surface coating technique to prepare the Li4SiO4-coated LiCoO2 composite (LiCoO2@Li4SiO4) to confront the issue of instability and increase the capacity of the LiCoO2 cathode at 4.5 V. Notably, the LiCoO2@Li4SiO4 electrode exhibits an exceptionally high initial discharge capacity (180.7 mA h g−1 at 0.1 C), a significantly enhanced rate capability (147.2 mA h g−1 at 5 C), and long-term cycling stability (capacity retention of 82.2% after 500 cycles at 2 C). The experimental results demonstrate that the Li4SiO4 coating could effectively reinforce the structural stability of the LiCoO2@Li4SiO4 electrode during cycling. Furthermore, the density functional theory calculation results further confirm that the Li4SiO4 coating facilitates the rapid Li+ diffusion at the LiCoO2@Li4SiO4 electrode. This work provides a potential strategy for interface engineering of the 4.5 V LiCoO2 cathode for high-energy-density LIBs.

Asymmetric structures have attracted much attention owing to their potential application in drug delivery, optoelectronics and catalysis. However, current reported works for the preparation of asymmetric particles rely mainly on emulsion, seeding, hydrothermal and templating approaches, but facile strategies are seldom developed. Herein, we first utilize low-cost monomers of thiourea and formaldehyde to fabricate a peculiar V-notched half-open polymer architecture via a facile precipitation polymerization method in a mixed solvent of water/ethanol (1 : 1 v/v) at room temperature, where the volume ratio between water and ethanol can adjust the open angle of the microspheres. Impressively, this method is readily carried out, and no templates, surfactants, hydrothermal devices, complex procedures or toxic solvents are utilized. This synthetic strategy provides a facile approach to prepare V-notched half-open polymer microspheres with potential for materials engineering.

Cobalt oxyhydroxide (CoOOH) is a promising anode material for lithium-ion batteries (LIBs) due to its high electronic conductivity (5 S cm−1) and theoretical specific capacity (1457 mA h g−1). Herein, CoOOH nanosheets are successfully obtained using a facile one-pot method, and a hierarchical nanoporous structure is formed by oxidizing cobalt hydroxide (Co(OH)2) in NaOH and (NH4)2S2O8 solution. The CoOOH anode shows better electrochemical performance compared to Co(OH)2 and Co3O4 electrodes when applied to LIBs. The hierarchical nanoporous structure and high electronic conductivity of the CoOOH anode contribute to its outstanding initial discharge capacity (1478 mA h g−1 at 0.2 A g−1), high initial coulombic efficiency (ICE, 90%), and excellent cyclability (1588 mA h g−1 after 300 cycles). Experiments and density functional theory (DFT) calculations confirmed that the high ICE and prominent rate capability (574 mA h g−1 at 5 A g−1) of the nanosheets could be ascribed to the rapid and complete conversion reaction of CoOOH upon lithiation/delithiation facilitated by hydroxyl groups and oxygen vacancies. This study provides new insights into the structure–property relationship of transition-metal oxyhydroxide anode materials for LIBs.

Solid-state electrolytes (SSEs) are promising alternatives to traditional liquid electrolytes because of their safety issues. However, polymer SSEs have low ionic conductivity and weak mechanical strength, and inorganic SSEs are very brittle and unstable to lithium metal and atmospheric moisture, which restricts their practical applications. To avoid these disadvantages, it is essential to develop polymer–inorganic composite SSEs. In this work, we for the first time construct a solid composite polymer electrolyte of poly(vinylidene fluoride hexafluoropropylene) (PVDF-HFP) blended with Li1.3Al0.3Ti1.7(PO4)3 and flower-like CeO2 particles enriched with oxygen vacancies as inorganic fillers. The composite SSEs exhibit a wide electrochemical window of 5.1 V (vs. Li/Li+) and high ionic conductivity of 1.66 × 10−3 S cm−1 at room temperature. The conductivity enhancement originates from the oxygen vacancies associated with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) for releasing more lithium ions, and CeO2 is also beneficial for the suppression of Li dendrites. The solid-state LiFePO4/SSE/Li cell exhibits superior electrochemical performance at room temperature, the capacity is as high as 166.6 mA h g−1 at 0.1C, and the cell can sustain 83.1 mA h g−1 at 2C after 1000 cycles.

A series of robust metallo-aerogels are readily fabricated by pyrolysis of xerogels derived from chitosan-metal (M = Fe, Co, Ni) hydrogels. Owing to the strong coordination between metal ions and the functional groups (NH2 and OH) of chitosan, metallo-aerogels consisting of encapsulated metal-nanoparticles (MNPs) by graphite shells were obtained, as supported by various characterizations including high-resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD), and Raman. The resulting metallo-aerogels could be functioned as highly stable, efficient and selective nanocatalysts towards the hydrogenation of nitroarenes to amines at low catalyst loading (1.2 mol.%−2.4 mol.%). Remarkably, the metallo-aerogels could be reused for more than 30 runs without obvious loss of activity and selectivity. These distinguished performances were attributed to the graphitic shells formed during the pyrolysis, which hampered the possible aggregation of MNPs, prevented metal leaching and increased their stability.

In this work, NiCo2O4(NCO) was synthesized via microwave hydrothermal method and a further annealing treatment. Research results have shown that the surface defects(Co2+ site) and pore size of the materials can be adjusted by simply changing the calcination temperatures, and porous nanowire arrays structure can be obtained. The porous structure is conducive to the penetration of the electrolyte and enables the NCO to fully participate in the electrochemical reaction. What’s more, the NCO material has ample space to buffer the volume change in the cycle test, improving the cycling stability. The NCO obtained at 350 °C has better performance. It exhibits a specific capacitance of 648.69 F/g at 1 A/g and good rate capability. Especially, at 10 A/g, the specific capacitance can still be maintained at 80.00% after 10000 galvanostatic charge/discharge(GCD) cycles, showing excellent cycling stability.

The electrochemical reduction of CO2 (CO2RR) can substantially contribute to the production of useful chemicals and reduction of global CO2 emissions. Herein, we presented N and S dual-doped high-surface-area carbon materials (SZ-HCN) as CO2RR catalysts. N and S were doped by one-step pyrolysis of a N-containing polymer and S powder. ZnCl2 was applied as a volatile porogen to prepare porous SZ-HCN. SZ-HCN with a high specific surface area (1510 m2 g−g1) exhibited efficient electrocatalytic activity and selectivity for CO2RR. Electrochemical measurements demonstrated that SZ-HCN showed excellent catalytic performance for CO2-to-CO reduction with a high CO Faradaic efficiency (~93%) at −0.6 V. Furthermore, SZ-HCN offered a stable current density and high CO selectivity over at least 20 h continuous operation, revealing remarkable electrocatalytic durability. The experimental results and density functional theory calculations indicated that N and S dual-doped carbon materials required lower Gibbs free energy to form the COOH* intermediate than that for single-N-doped carbon for CO2-to-CO reduction, thereby enhancing CO2RR activity.

The development of appropriate catalysts with relatively low cost, good selectivity and excellent stability is one of the major issues in electrochemical reduction of CO2. In this work, an efficient electrocatalyst was fabricated via ultra-small Co3O4 nanoparticles encapsulated within the tip of carbon nanotubes, denoted as Co/CNTs. Benefiting from the synergistic effects of highly active Co3O4 nanoparticles and well-graphitized carbon nanotubes, Co/CNTs exhibited remarkable performance in CO2 electroreduction. In a conventional H-type cell, CO with a 90% faradaic efficiency and 20.6 mA cm−2 partial current density was obtained at only −0.7 VRHE cathode potential with 40 hour stability. Upon switching to a gas-diffusion device, the CO partial current density could reach as high as 232.6 mA cm−2 with >80% faradaic efficiency, which might be even comparable to that of state-of-the-art CO2 electrocatalysts. Our work could also provide a new strategy for developing non-noble metal catalysts for CO2 electroreduction.

The high-temperature calcination of metal–organic frameworks (MOFs) often leads to a sharp collapse in the abundant pores inside the MOFs and a serious aggregation of metal sites, which are adverse to electrocatalysis performance. Here, a controllable calcination route was developed for the partial decomposition of ultrathin 2D Ni-based MOF (2D Ni-MOF) precursors to fabricate ultrafine NiO nanoparticles (NPs) within the ultrathin 2D Ni-MOF. In particular, 2D Ni-MOF precursors (thickness: ∼2 nm), for the first time, were rapidly synthesized via a microwave-assisted solvothermal method. The controllable calcination route effectively retained the ultrathin 2D porous nanostructure of the MOFs, and simultaneously enabled the formation of defect-rich ultrafine NiO NPs within the 2D Ni-MOF. Benefiting from the unique nanostructure (i.e., ultrathin 2D nanosheets) and highly active sites (i.e., defect-rich NiO NPs), the partially decomposed 2D Ni-MOF-250 exhibited excellent performance for oxygen evolution reaction (OER) with an overpotential of 250 mV at 50 mA cm−2 in 1 M KOH, outperforming those obtained from other reported nonprecious-metal-based electrocatalysts. More importantly, 2D Ni-MOF-250 could achieve the industry-related current density of 1000 mA cm−2 at a small overpotential of 410 mV, demonstrating its promising potential for use in practical applications. Therefore, the controllable calcination route may stand out as a facile yet robust route for smartly fabricating defect-rich metal oxides within MOFs toward efficient electrocatalysis.

Carbon dioxide electroreduction provides a useful source of carbon monoxide, but comparatively few catalysts could be sustained at current densities of industry level. Herein, we construct a high-yield, flexible and self-supported single-atom nickel-decorated porous carbon membrane catalyst. This membrane possesses interconnected nanofibers and hierarchical pores, affording abundant effective nickel single atoms that participate in carbon dioxide reduction. Moreover, the excellent mechanical strength and well-distributed nickel atoms of this membrane combines gas-diffusion and catalyst layers into one architecture. This integrated membrane could be directly used as a gas diffusion electrode to establish an extremely stable three-phase interface for high-performance carbon dioxide electroreduction, producing carbon monoxide with a 308.4 mA cm−2 partial current density and 88% Faradaic efficiency for up to 120 h. We hope this work will provide guidance for the design and application of carbon dioxide electro-catalysts at the potential industrial scale., Here the authors deploy Ni single atom-decorated carbon membranes as integrated gas diffusion electrodes to construct an extremely stable three-phase interface for CO2 electroreduction, producing CO with a partial current density of 308.4 mA cm–2 and a Faradaic efficiency of 88% for up to 120 h.

This study presents low-crystalline and non-stoichiometric cobalt oxide (Co3−xO4−δ) porous nanosheet arrays (PNAs) grown on carbon fiber cloth (CFC) (Co3−xO4−δ PNAs/CFC) by a facile in situ anodic oxidation strategy. We firstly verified that the above prepared low crystalline cobalt oxide contained tetrahedral CoO4 vacancies, resulting in the creation of O vacancies at adjacent octahedral CoO6 sites, allowing the generation of tetragonal–pyramidal CoO5 sites which were regarded as active sites and being accessible for the oxygen evolution reaction (OER) with different reaction mechanisms compared to that of traditional CoO6 sites in high-crystalline and stoichiometric Co3O4, thus endowing Co3−xO4−δ PNAs/CFC with significantly improved OER activity and superior stability compared to their crystalline counterparts (Co3O4 PNAs/CFC), as illustrated by experiments and density functional theory (DFT) calculations. This study will open up a new approach for the synthesis of defect-rich materials and provide new insight into the structure–property relationship of OER catalysts.

The hydrogen evolution reaction (HER) in alkaline solution has attracted considerable interest, but it is limited by the kinetically sluggish water dissociation step. Herein, we report single-atom Pt immobilized in the lattice of CoP mesoporous nanosheets (MNSs) grown on carbon fiber cloth (CFC) (Ptat–CoP MNSs/CFC) with ultralow Pt loading (0.7 wt% relative to CoP, 5.89 μg cmgeo−2) as a high-performance electrocatalyst for the HER in alkaline solution. Assisted by the strong interaction between Ptat and CoP, water dissociation becomes spontaneous, providing Ptat–CoP MNSs/CFC with a low HER kinetic barrier. Accordingly, Ptat–CoP MNSs/CFC exhibits outstanding HER performance with negligible onset potential, super high catalytic activity, and excellent durability that is even superior to the commercial 20 wt% Pt/C catalyst. Moreover, Ptat–CoP MNSs/CFC exhibits excellent catalytic activity and stability toward seawater electrolysis.

Electrocatalytic reduction reaction of CO2 (CO2RR) is an effective way to mitigate energy and environmental issues. However, very limited catalysts are capable of converting CO2 resources into high-value products such as hydrocarbons or alcohols. Herein, we first propose a facile strategy for the large-scale synthesis of isolated Cu decorated through-hole carbon nanofibers (CuSAs/TCNFs). This CuSAs/TCNFs membrane has excellent mechanical properties and can be directly used as cathode for CO2RR, which could generate nearly pure methanol with 44% Faradaic efficiency in liquid phase. The self-supporting and through-hole structure of CuSAs/TCNFs greatly reduces the embedded metal atoms and produces abundant efficient Cu single atoms, which could actually participate in CO2RR, eventually causing -93 mA cm-2 partial current density for C1 products and more than 50 h stability in aqueous solution. According to DFT calculations, Cu single atoms possess a relatively higher binding energy for *CO intermediate. Therefore, *CO could be further reduced to products like methanol, instead of being easily released from the catalyst surface as CO product. This report may benefit the design of efficient and high-yield single-atom catalysts for other electrocatalytic reactions.

Recently, metal‐free, heteroatom‐doped carbon nanomaterials have emerged as promising electrocatalysts for the oxygen evolution reaction (OER), but their synthesis is a tedious process involving energy‐wasting calcination. Molecular electrocatalysts offer attractive catalysts for the OER. Here, phytic acid (PA) was selected to investigate the OER activity of carbons in organic molecules by DFT calculations and experiments. Positively charged carbons on PA were very active towards the OER. The PA molecules were fixed into a porous, conductive hydrogel with a superhydrophilic surface. This outperformed most metal‐free electrocatalysts. Besides the active sites on PA, the high OER activity was also related to the porous and conductive networks on the hydrogel, which allowed fast charge and mass transport during the OER. Therefore, this work provides a metal‐free, organic‐molecule‐based electrocatalyst to replace carbon nanomaterials for efficient OER.

In this paper, a simple one-step doping spray method using liquid polyacrylonitrile (LPAN) is reported, for the preparation of LiNi0.8Co0.15Al0.05O2 (NCA) precursor, after calcination, to obtain a loose and porous sphere-shaped NCA (LPAN@NCA). The initial discharge specific capacity was found to be 227.9 mA h g−1 at 0.1C, which is 26.6% higher than that of the pristine sample. Its capacity retention rate was found to be 93.59% after 200 cycles, and the surface morphology of the material grains after the cycles remains intact. X-ray diffraction (XRD) analysis reveals that doping with LPAN can effectively decrease the amount of disorder of Ni2+ in Li + position that gets reduced by 2.72%. The X-ray photoelectron spectroscopy (XPS) analysis shows that after the carbonization of LPAN, the C atoms replace part of O atoms, effectively forming a new compound. The decrease in the impedance of the battery materials before and after the cycle and the increase of lithium ion mobility also confirms the effectiveness of LPAN doping. The LPAN@NCA prepared by in-situ doping of LPAN by spraying method is simple and effective, which exhibits high specific capacities, superior rate performance and excellent recycling stability, that has a good commercial application prospect.

Regulation of the electronic structures of metal centers represents a robust strategy for enhancing the activity of electrocatalysts. Herein, we report the crafting of hybrid electrocatalysts comprising both single atomic Ru (SA-Ru) and Ru nanoparticles (NPs) supported on porous N-doped carbon (PC), in which the electronic structures of SA-Ru were effectively optimized by nearby Ru NPs to achieve great enhancement of the hydrogen evolution reaction (HER). The resulting SA-Ru/Ru NPs/PC displayed ultrahigh activity for HER in 1 M KOH with a mass activity of 4.2 mA μgRu−1 at −0.07 V vs. RHE; this activity was 14 times that of commercial Pt/C, representing the largest reported value among the Pt-free electrocatalysts. In addition to the ultrahigh activity, the composite possessed the outstanding stability of 24 h and rapid HER kinetics (i.e. Tafel slope: 31.8 mV dec−1). The experimental and theoretical results matched well with each other and unambiguously indicated that the control over the electronic structures of SA-Ru and the advantageous PC support (i.e. its hierarchical porous nanostructures and superhydrophilic surface) jointly contributed to the exceptional performance.

The ability to develop low-cost electrocatalysts with high efficiency and strong stability for acid oxygen evolution reactions (OER) will enable commercial applications of powerful proton exchange membranes (PEM) in water splitting devices. However, this remains challenging because most nonprecious metal-based electrocatalysts suffer from strong corrosion in acid media. Herein, we crafted porous N, S-doped carbon network-immobilized ultrafine pentlandites (i.e., Ni4Fe5S8) nanoparticles (denoted P-NSC/Ni4Fe5S8-1000) by employing rationally designed nanohybrids comprised of liquid polymer-coated binary Prussian blue analogue (PBA) nanoparticles (NPs) as precursors. Afterwards, the P-NSC/Ni4Fe5S8-1000 nanocomposites were exploited as OER electrocatalysts, with a small onset potential of 1.53 V vs. RHE (1 mA cm−2) and strong stability in 0.5 M H2SO4 solution, outperforming commercial RuO2 electrocatalysts. As revealed by both experimental results and DFT calculations, there is a synergy effect on the P-NSC/Ni4Fe5S8-1000 for OER: the pyridinic-N, S doped carbon could easily adsorb water, and then the highly active Fe sites of Ni4Fe5S8 NPs could catalyze the absorbed water to oxygen gas. Furthermore, the hierarchically porous nanostructure could promote multiphase transport during acid OER. Therefore, this work, for the first time, highlighted the great potential of pentlandites NPs-based nanocomposites as efficient and stable electrocatalysts for acid OER.

Polyacrylonitrile (PAN) is an attractive precursor for N-doped porous carbons owing to its high nitrogen content and good thermal stability. Herein, a facile and effective route for the synthesis of N/S co-doped porous carbon by capitalizing on hetero-atom containing PAN as a doped carbon source and ZnCl2 as a volatile porogen is reported. Notably, the optimal porous carbon (denoted as FeZ-CNS-900) with a large specific surface area of up to 1730 m2 g−1 exhibits excellent oxygen reduction reaction (ORR) activity with a half-wave potential of 0.881 V, which is 39 mV more positive than that of commercial Pt/C under alkaline conditions, as well as robust durability and methanol tolerance. Interestingly, the use of N/S co-doped porous carbon also offers comparable ORR activity yet much higher stability than that of Pt/C under acidic conditions. Finally, the implementation of FeZ-CNS-900 as the air-cathode catalyst for primary Zn–air batteries yields an open-circuit potential of 1.49 V, a high peak power density of 168 mW cm−2, a large specific capacity of 778 mA h gZn−1 (corresponding to an energy density of 1020 W h kgZn−1) and a remarkable durability.

The development of noble metal-free catalysts, which can replace noble metal ones, such as Pt, for various electrocatalytic processes in renewable energy devices is currently of huge interest. The β-phase of molybdenum carbide (i.e., β-Mo2C) has been reported to be one of the most active noble metal-free electrocatalysts for the hydrogen evolution reaction (HER) in electrolyzers, whereas the other phases, MoC and MoC1−x, have been widely regarded as weak electrocatalysts for HER. Herein, we report the synthesis of nanoporous substoichiometric α-MoC1−x and η-MoC nanosheets, named np-MoC NSs, that show comparable electrocatalytic activity toward HER as β-Mo2C does. The materials are synthesized using two-dimensional (2D) conjugated carbonitride and ammonium molybdate as precursors. Their structures contain N dopant atoms and nanopores. The pores create highly accessible catalytic sites and good mass and charge transport, and thereby excellent reaction kinetics for HER, in the materials. Theoretical calculations show that the N dopant atoms modulate the electronic properties of the catalytically active sites in the materials, leading to lower free energy of adsorption and desorption for the hydrogen species involved in the reaction and better catalytic activity for HER. This work demonstrates that, by simple structural design and electronic modulation, various phases of molybdenum carbides and related materials that have been traditionally considered inactive catalysts for HER can be made robust electrocatalysts for the reaction.

Bottom-up construction of transition copper–nitrogen–carbon (Cu–N–C) electrocatalysts with high-performance and long-term durability for the oxygen reduction reaction (ORR) still remains a great challenge. Herein, we propose a temperature-controlled synthesis strategy with confinement effect for fabrication of a novel two-dimensional dual-metal (Cu/Zn) zeolitic imidazolate framework material, which presents an ultrathin nanosheet morphology after high-temperature thermal treatment (denoted as Cu–N-UNS). By controlling the reaction temperature as well as regulating the ratio of metal ions and taking advantages of the confinement effect of surfactants, the rationally designed ultra-thin carbon layer not only prevents aggregation of transition Cu particles and avoids direct contact with reactants and electrolyte solutions to enhance the durability of electrocatalysts, but also shortens the electronic transmission path between the active transition metal species and carbon surface. Therefore, the electrocatalyst exhibits excellent electrocatalytic performance for the ORR (E1/2 ≈ 0.898 V), which is superior to those of state-of-the-art benchmark noble-metal electrocatalysts. Moreover, the even distribution of Cu–N–C and existence of N–Cu2+–Cu0 active sites make a great contribution to the electrocatalyst activity. Notably, the Cu–N-UNS used as air electrodes for Zn–air batteries also exhibits a high peak power density of ≈134.7 mW cm−2 at a current density of ≈231.9 mA cm−2 with remarkable durability.

A novel core-shell structure of Co/N-doped carbon polyhedron@NiCo layered double hydroxides (Co/NCP@NiCo-LDHs) was designed and synthesized. Except for the advantages of core-shell structure of the electronic redistribution at the heterostructure and exposure of numerous active sites, metallic Co encapsulated into NCP was proved to be crucial to fine-tune the electronic transfer between NCP and NiCo-LDHs. The above merits rendered Co/NCP@NiCo-LDHs with improved oxygen evolution reaction (OER) activity with a low overpotential of 277 mV at 10 mA cm−2 in 1 M KOH solution, which is much better than the Co/NCP, NiCo-LDHs and NCP@NiCo-LDHs, and showed quite high durability. This strategy is demonstrated to be a reliable approach for improving the catalytic efficiency of LDHs catalysts.

A facile route to scalable production of N and S co-doped, hierarchically porous carbon nanofiber (NSHCF) membranes (ca. 400 cm2 membrane in a single process) is reported. As-synthesized NSHCF membranes are flexible and free-standing, allowing their direct use as cathodes for efficient electrochemical CO2 reduction reaction (CO2 RR). Notably, CO with 94 % Faradaic efficiency and -103 mA cm-2 current density are readily achieved with only about 1.2 mg catalyst loading, which are among the best results ever obtained by metal-free CO2 RR catalysts. On the basis of control experiments and DFT calculations, such outstanding CO Faradaic efficiency can be attributed to the co-doped pyridinic N and carbon-bonded S atoms, which effectively decrease the Gibbs free energy of key *COOH intermediate. Furthermore, hierarchically porous structures of NSHCF membranes impart a much higher density of accessible active sites for CO2 RR, leading to the ultra-high current density.

Hydrogen generation by electrochemical water splitting with the renewable power source is one of the most promising pathways for green and sustainable society. The challenge is to explore a simple and cost-effective method to synthesize earth-abundant and noble-metal-free electrocatalysts with reliable hydrogen evolution reaction (HER) activity. Herein, we report a facile and scalable method to synthesize hybrid MoS2 and nickel sulfides (NiS/NiS2/Ni3S4) nanosheets (Mo-Ni-S NSs) with highly efficient HER activity in alkaline media. The hybrid phase and NSs allow large exposure of edge sites of MoS2 and construct highly active hetero-interfaces between MoS2 and NiSx and sufficient durability in alkaline solution. Mo-Ni-S NSs with optimal composition presents a low overpotential of 83 mV to reach a current density of 10 mA cm−2 in 1.0 M KOH, which is comparable to the performance of recent reported highly active MoS2 based electrocatalysts. This work sheds light on the facile synthesis of multiple heterostructures as efficient electrocatalysts for scalable application in energy chemistry.

Numerous catalysts have been successfully introduced for CO2 fixation in aqueous or organic systems. However, a single catalyst showing activity in both solvent types is still rare, to the best of our knowledge. We developed a core-shell-structured AgNW/NC700 composite using a Ag nanowire (NW) core encapsulated by a N-doped carbon (NC) shell at 700 °C. Through control experiments and density functional theory calculations, it was confirmed that Ag nanowires acted as the active sites for CO2 fixation and the uniformly coating of N-doped carbon created a CO2 -rich environment around the Ag nanowires, which could significantly improve the catalytic activity of Ag nanowires for electrochemical CO2 fixation. Under mild conditions, up to 96 % faradaic efficiency of CO, 95 % yield of Ibuprofen and 92 % yield of propylene carbonate could be obtained in the electrochemical CO2 direct reduction, carboxylation and cycloaddition, respectively, using the same AgNWs/NC700 catalyst. These results might provide an alternative strategy for efficient electrochemical fixation of CO2 .

In the past few decades, much attention has been paid to developing electrocatalysts with low cost and high efficiency for the hydrogen evolution reaction (HER) because of its potential impact on the energy fields. Besides, recent research demonstrates that interfaces play an important role in the electrocatalytic process. Herein, C/N-co-doped Pd coated Ag (Ag@Pd) nanowires (NWs) were prepared through a calcination process. In this process, the C/N–Ag@Pd interfaces consisted by the Pd-N bonds and the core/shell structure of Ag@Pd were formed. The effect of the calcination temperature on the formation of the C/N–Ag@Pd interfaces were investigated in detail. Moreover, C/N-co-doped Ag@Pd NWs exhibited excellent catalytic activity for HER with a small overpotential of 111 mV to afford a current density of 10 mA cm−2, a low Tafel slope of 64 mV Dec−1 and good stability. The relationship between the HER activity and the C/N–Ag@Pd interfaces were built. Furthermore, such design principle for constructing interfaces between noble metal alloys and C/N by direct sintering can offer a new strategy for the developing more efficient electrocatalysts.

The efficient and sustainable production of high-purity hydrogen gas through electrochemical water splitting calls for robust and bifunctional catalysts to accelerate the two half reactions of water splitting. Herein, we in-situ craft ultrathin CoNi-sulfides nanosheet (∼2.2 nm in thickness) arrays-anchored MnO2 nanoparticles (∼3.2 nm in diameter) (denoted U-CoNi-S-NSA/MnO2) via a spontaneous redox process between CoNi-sulfides nanosheet and MnO4− anions at ambient temperature. The hierarchical U-CoNi-S-NSA/MnO2 nanocomposites are then directly employed as self-supported catalysts for the two half reactions of water splitting, showing excellent activity with small overpotentials of 170 mV for oxygen evolution reaction and 67 mV for hydrogen evolution reaction to achieve 10 mA cm−2, respectively. Moreover, an efficient water electrolyzer through using U-CoNi-S-NSA/MnO2 as both anodic and cathodic catalysts is fabricated, which achieves current density of 10 mA cm-2 at a small voltage of 1.51 V over a long-time operation of 20 h. This outstanding performance is markedly superior than that of precious Pt/C//RuO2 counterpart (1.61 V). Therefore, the as-synthesized hierarchical nanocomposites are promising candidates for cheap and efficient water splitting.

Electrochemical water splitting by electricity from the renewable power sources is one of the most promising pathways for green and sustainable hydrogen production. The key is to synthesize earth-abundant and noble-metal-free electrocatalysts with outstanding hydrogen evolution reaction (HER) activity and durability in wide-pH electrolytes by simple and cost-effective methods. Herein, we reported a one-step synthesis of uniform, ultrafine molybdenum carbide (Mo2C) and molybdenum nitride (Mo2N) hybrid [together as Mo2(CN)] inserted carbon nanosheets as efficient electrocatalyst for HER. The as-synthesized catalyst showed an excellent HER activity in acid medium, and even superior performance was obtained in the alkaline medium. The optimal Mo2(CN) annealed at 750 °C showed an overpotential of −80 mV at 10 mA cm−2 and a Tafel slope of 40 mV dec−1; the former strikingly outperforms commercial 20% Pt/C materials (−112 mV). Moreover, Mo2(CN) gave an onset voltage of −33 mV and overpotential of −202 mV at 100 mA cm−2 with merely a mass loading of 0.2 mg cm−2, which are, to date, among the best records for Mo-based catalysts in both media. The nanosheet structure providing large active area and quick charge transfer, and the synergistic effects between Mo2C and Mo2N toward HER are ascribed to the outstanding electrocatalytic activity according to the capacitive current and turnover frequency analysis. The remarkable catalytic activity and operational durability in wide pH ranges guarantee their potential for highly efficient hydrogen production.

Despite recent vigorous progress in synthesis of monofunctional electrocatalysts for hydrogen evolution reaction (HER) or oxygen evolution reaction (OER), it remains challenging to develop bifunctional electrocatalysts for efficient overall water splitting. Herein, we report the crafting of MoC2-doped NiFe alloy nanoparticles (NPs) encapsulated within a-few-layer-thick N-doped graphene (denoted NG-NiFe@MoC2) via one-step calcination of hybrid precursors containing polymer-encapsulating binary Prussian blue analogues NPs and Mo6+ cations. The resulting NG-NiFe@MoC2 nanohybrids were exploited as electrocatalysts and exhibited excellent performance on either HER or OER separately as a direct consequence of the synergistic effects of unique compositions (i.e., MoC2 dopants and NiFe alloy NPs; both exerted profound influence on HER and OER) and advantageous architecture (i.e., a-few-layer-thick N-doped graphene encapsulating shell). Remarkably, an alkaline electrolyte capitalizing on NG-NiFe@MoC2 nanohybrids as bifunctional electrocatalysts achieved overall water-splitting (i.e., concurrent HER and OER) current density of 10 mA cm−2 at a low potential of 1.53 V over a period of 10-h operation, outperforming the precious Pt/C//RuO2 counterpart.

In this report, Pt/NCNFs/Cu-foil, an efficient and stable catalyst, was prepared by the electrospinning method, which could be directly used for electrochemical reduction of CO2. Formate with 93% Faradaic efficiency and about 46 mA cm−2 partial current density could be obtained at −0.6 VRHE; alcohols with approximately 35% Faradaic efficiency and 14 mA cm−2 partial current density were achieved at −1.0 VRHE using the same Pt/NCNFs/Cu-foil cathode. Moreover, Pt/NCNFs/Cu-foil could keep high efficiencies for at least 50 h durability tests. Keywords: CO2 reduction, Electrocatalysis, High catalyst productivity, Excellent reusability, Electrospinning technology

Highly efficient, cost-effective and environmental-friendly electrocatalysts play a crucial role in oxygen reduction reaction (ORR) for fuel cells and metal-air batteries. Herein, a series of hybrids comprising of NiCo alloy, metal oxides and carbon black were readily prepared by a one-pot pyrolysis approach and employed as efficient ORR electrocatalysts in the alkaline media. Different amounts of Ketjen Black EC 300J (EC) with a large mesoporous area and exceptional electrical conductivity were directly added to synthesize the hybrids. Among the hybrids tested, the NC-MMO-EC-3 (where NC stands for NiCo alloy and MMO for mixed metal oxides) with an appropriate amount of EC displayed the best ORR electrochemical activity. The enhanced activity of the NC-MMO-EC-3 could be attributed to the conductivity improved by EC, the high dispersion of MMO and NC on EC support, and the beneficial interaction among those three components.

Current commercially available dental composite materials have certain limitations for their use, including high monomer viscosity and high polymerization shrinkage, resulting in residual stresses and interfacial gaps. This study focused on the chemical modification of resin monomer bisphenol A-glycidyl methacrylate (bisGMA), so as to reduce the viscosity and polymerization shrinkage. In this design, the hydroxyl groups of bisGMA were transformed into ester groups with various alkyl chain length and branching. The modified monomers showed promising properties including reduced viscosity, reduced polymerization shrinkage, increased hydrophobicity, increased degree of double bond conversion, and improved mechanical properties of the resulting dental resin composites. The structure/property relationships of the new monomers were investigated, and optimal monomer structures were identified for dental composites with improved properties.

The ability to develop low-cost highly efficient electrocatalyst for oxygen evolution reaction (OER) is key to the overall water splitting device that represents a viable and promising source of alternative energy. Herein, we crafted three-dimensional (3D) network comprising nitrogen-doped graphitic carbon-coated heterojunctions (denoted NC-Ni0.36Fe0.64/MnOx) via one-step calcination of hybrid precursors containing ternary Prussian blue analogues and polymers. The NC-Ni0.36Fe0.64/MnOx nanocomposites were then exploited as catalysts for OER, displaying exceptional performance with a small overpotential of 300 mV to reach 10 mA cm−2, a low Tafel slope of 43 mV/dec and an outstanding stability without deactivation over a 10-h OER. Notably, compared to commercial RuO2 catalysts, NC Ni0.36Fe0.64/MnOx catalysts demonstrated much lower overpotential and Tafel slope. The excellent OER performance can be attributed to the presence of high-valence oxidized metal species (Ni2+, Fe2+ and Mn2+) at the heterostructured interface as well as pyridinic N-doped carbon species on highly conductive graphitic carbon network, thus greatly facilitating the electron-withdrawing from OH− and thus charge transfer during OER. This simple yet effective strategy may open new possibilities for creating a wide range of low-cost, high-efficiency, non-precious transition metal OER catalysts for the overall water splitting.

Development of robust, bifunctional, and non-precious catalysts for oxygen and hydrogen evolution reactions (OER and HER) is a prerequisite to realizing the overall splitting of water. This, however, remains a great challenge. In this context, we fabricated a novel three-dimensional (3D) network comprising N-doped carbon-coated core–shell NiFeOx@NiFe–P (denoted as NC–NiFeOx@NiFe–P) by two-pot high-temperature phosphorization and surface oxidation of a NiFe-Prussian blue analogue/polyvinylpyrrolidone (denoted as NiFe–PBAs/PVP) hybrid precursor. The as-synthesized NC–NiFeOx@NiFe–P catalyst demonstrated exceptional performance for both OER and HER, offering a current density of 10 mA cm−2 (a metric related to solar fuel) at small overpotentials of 285 mV for the OER and 237 mV for the HER in 1 M KOH, respectively. As expected, a NC–NiFeOx@NiFe–P based alkaline electrolyzer with durability of 20 h was manufactured to achieve 10 mA cm−2 at a voltage of 1.59 V, outperforming most non-precious metal-based electrolyzers. The exceptional performance could be attributed to the unique 3D network composed of core–shell NiFeOx@NiFe–P and highly conductive N-doped carbon (NC), which provided a large amount of highly active sites for both OER and HER and favored fast electron transport during electrocatalytic processes.

A novel Pt-NP@NCNF@CC composite was prepared by the electrospinning technique. It is a highly efficient and binder-free catalyst for the direct reduction and carboxylation of CO2 with halides. Formate with 91% Faradaic efficiency and 2-phenylpropionic acid with 99% yield could be obtained, respectively. Moreover, this catalyst has excellent stability and reusability.

Solid-state lithium metal batteries (SSLMBs) are promising candidates for the application in electric vehicles (EVs) because of their higher energy density and safer properties compared to the traditional liquid organic electrolyte-based lithium-ion batteries (LIBs). However, SSLMBs with solid polymer electrolyte (SPE) suffer from the serious lithium dendrite problem, which results in the poor cycling performance and the short circuit of batteries. In this work, a thin and flexible blended gel polymer electrolyte (GPE) was prepared for dendrite free SSLMBs. The as-prepared GPE has a strong strain at 529.94 ± 10%, a high ion transference number (tLi+) of 0.66, and a wide electrochemical window of 5.23 V (vs. Li+/Li). Mechanism study shows that the addition of fluoroethylene carbonate (FEC) into the GPE promotes the formation of LiF-coating solid electrolyte interphase (SEI). As a result, a stable GPE/Li-metal interface and dendrite-free SSLMB was achieved. Moreover, the solid-state battery with Li-metal anode, as-prepared SPE and LiFePO4 can deliver a specific capability of 150 mAh g−1 and a capacity retention of 94.8 % after 500 cycles at 0.3C, 20 ℃.

A facile construction of Ru/RuO2 composite with porous reticular structure (denoted as Ru/RuO2-PRS) by controllable pyrolysis of Ru3+ coordinated cyanoguanidine was presented for oxygen evolution reaction (OER). The Ru/RuO2 heterostructure was identified in Ru/RuO2-PRS. Taking the advantages of the Ru/RuO2 heterostructure and large specific surface area, Ru/RuO2-PRS exhibits much more improved OER activity with much lower onset potential and overpotential to reach the current density of 10 mA cm−2 compared with RuO2 porous powder and RuO2 nano-particles counterparts in both acidic and alkaline solution. Specifically, Ru/RuO2-PRS exhibits much improved durability because the unique Ru/RuO2 heterostructure relieves the dissolution of RuO2 at high anodic potential that has been the bottleneck of Ru-based catalysts for OER, especially in acidic electrolyte. This study provides a new strategy to promote the OER application in acidic solution.

Exploring of electrocatalysts for high-output oxygen evolution reaction (OER) is key to practical applications, but still remains challenging. Here, we developed a nature-inspired etching strategy for the construction of karst topography (KT)-featured electrode comprising core-shell structured Ni(0)@Ni(II) towards efficient OER. Intriguingly, the KT architecture confers a “superaerophobic” surface to render the large amount of generated O2 bubbles release rapidly and timely from the electrode surface at the high current density of OER (i.e., 1500 mA cm−2). Moreover, this strategy allows good control over the generated core-shell structure for promoting the heterointerface synergetic effect of Ni(0)@Ni(II). By adding probing molecules to react with OER intermediates under operation conditions, we obtain first direct experimental evidence that the core-shell structure can optimize the adsorption strength of *OH for significantly boosting the OER kinetics. Notably, the obtained electrode has excellent performance for OER with a small overpotenital of 380 mV at 1500 mA cm−2.

Li 4 Ti 5 O 12 particles are synthesized coated with very thin graphene-like sheets in situ using liquid-polyacrylonitrile (LPAN) as the carbon source and added utilized conductivity additives to improve the conductivity of the electrode materials. The crystalline structures of Li 4 Ti 5 O 12 with 20% LPAN and different conductivity additives composites were examined by XRD. The structure and electrochemical performance of the graphene-like sheets coated Li 4 Ti 5 O 12 , with conductivity additives added, was systematically investigated. The electrochemical performance also revealed that the graphene-like sheets significantly improved the discharge capacity and cycling stability of Li 4 Ti 5 O 12 . In particular, the coated Li 4 Ti 5 O 12 with 20 wt% LPAN and 1% acetylene black (CB) reached 166.2 mAh g −1 at 10C. The performance improvement is a result of the graphene-like nanosheet conformal coating, which creates an electrically conductive network for the electrode.

Three-dimensional nickel oxide/graphene aerogel nanocomposites (NiO/GA) were synthesized via a simple solvothermal-induced self-assembly process. The structural and morphological properties of the NiO/GA were characterized with XRD, FE-SEM and TEM measurements. The nickel oxide was electrochemically deposited into the highly porous GA to form NiO/GA composites. In the three-electrode system, an extremely wide working potential window was observed from −1 to 1 V in 6 M aqueous KOH. A specific capacitance as high as 587.3 F g−1 was obtained at a constant current density of 1 A g−1. More importantly, the cycling stability of the NiO/GA was great with a tiny decay in specific capacitance after 1000 cycles at 1 A g−1.

Low-cost resorcinol formaldehyde (RF) organic aerogels were prepared by using resorcinol and formaldehyde as precursors, and sodium hydroxide as a catalyst through a single-mode microwave radiation-assisted sol-gel method and ambient temperature drying. Because of the ring focusing and power-max technology, the fabrication procedure of carbon aerogels (CAs) are much easier, faster, and cheaper than traditional methods. The RF aerogels were then pyrolysized at 900 &deg, C, and the KOH activation process was used to further dredge micropores in the carbon aerogels. The CAs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption/desorption, and a series of electrochemical tests. The KOH activated carbon aerogels with 3D-nano-network structure exhibited a high specific surface area of 2230 m2 g&minus, 1 with appropriate pore volumes of micro-, meso-, and macropores. The specific capacitance of CAs activated by KOH measured in a two-electrode cell was 170 F g&minus, 1 at 0.5 A g&minus, 1 with excellent rate capability and cycle stability in 6 M KOH electrolyte.

Herein we present a novel multi-level structure of Fe-doped NiO coupled Ni cluster hollow nanotube arrays (Fe-NiO-Ni CHNAs) grown on carbon fiber cloth as an efficient catalyst for oxygen evolution reaction. In this multi-level structure, rocksalt-type Fe-doped NiO phase hybrids with Ni clusters coupled into the nanospheres anchored to the outside of nanotube, forming a unique 3D corn-like structure. This novel multi-level structure represents a large specific area for catalytic reaction. X-ray absorption fine structure indicates that the defect-rich Fe-doped NiO phase has abundant coordinative unsaturated sites as active sites, and Fe doping downshifts the d-band of metal sites, which is the main contribution to the improved oxygen evolution reaction catalytic activity. The OER of Fe-NiO-Ni CHNAs obeys the adsorbate evolution mechanism with the nonconcerted proton-electron transfer pathway as a rate-determining step. Thus Fe-doped NiO CHNAs exhibits excellent OER performance and outstanding durability that surpasses most of transition metal oxides.

Non-noble-metal catalysts have shown promising oxygen reduction reaction (ORR) activity in proton exchange membrane fuel cells (PEMFCs). Herein, by using sulfur-terminated fluidic acrylonitrile telomere (ANT) as precursor, an N and S dual-doped Co/ANT/C catalyst was prepared via a facile heat treatment of the mixture of Co salt, ANT and carbon black, in which cobalt salt was uniformly-dispersed and interacted with ANT. As such, the increasing contact area between ANT and cobalt salt leads to a highly catalytic activity toward oxygen reduction reaction. Most importantly, by using ANT as precursor, the catalyst showed a remarkable improvement in the onset potential and current density as compared with those prepared from pure carbon black, cobalt salt/C or catalyst using high molecular weight polyacrylonitrile as precursor. Besides, the as-made Co/ANT/C catalyst demonstrated a comparable catalytic activity with commercial expensive Pt/C at high loading. In addition, the catalyst participated promotes a direct four-electron reduction of O2 to H2O and long term operation stability in an alkaline medium. Owing to its superb ORR performance, low cost and facile synthesis approach, such prepared Co/ANT/C catalyst has great potential applications in PEMFCs.

This work reports an investigation of the impact of microstructure on the performance of solid oxide fuel cells (SOFC) composed of nickel yttria-stabilized zirconia (Ni YSZ). X-ray nano computed tomography (nano-CT) was used to obtain three-dimensional (3D) models of Ni-YSZ composite anode samples subjected to different thermal cycles. Key parameters, such as triple phase boundary (TPB) density, were calculated using 3D reconstructions. The electrochemical reaction occurring at active-TPB was modeled by the Lattice Boltzmann Method for simulation of multi-component mass transfer in porous anodes. The effect of different electrode geometries on the mass transfer and the electrochemical reaction in anodes was studied by TPB distributions measured by nano CT for samples subjected to different thermal cycles. The concentration polarization and the activation polarization were estimated respectively. The results demonstrate that a combined approach involving nano-CT experiments in conjunction with simulations of gas transport and electrochemical reactions using the Lattice Boltzmann method can be used to better understand the relationship between electrode microstructure and performance of nickel yttria-stabilized zirconia anodes.

Cu6Sn5/carbon nanotubes (CNTs) composite materials were synthesized by reductive co-precipitation method. Their morphologies, microstructures and electrochemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), constant current charge/discharge tests, cyclic voltammetry tests (CV) and electrochemical impedance spectroscopy (EIS). The large surface area, excellent conductivity and mechanical properties of the CNTs reduced the agglomeration of alloy particles, buffered the stress of volume change and lowered the powdering rate of particles, simultaneously, maintaining the cycling stability and increasing Li+ transmissions and effectively whittling the contact resistance. The Cu6Sn5/CNTs composites alloy anode materials exhibited a better electrochemical performance and cycle life than those of any other composite alloy anode materials, demonstrating a capacity of 409 mAh/g after 50 cycles at voltage range of 0.02–1.5 V, at the current density 0.05 mA/cm2.

Manganese dioxide/graphene composite is receiving intensive attention because of its potential applications in energy storage field. In this paper, a novel MnO2 nanocomposite material for high performance supercapacitor was prepared in situ on graphene-like membrane using liquid-polyacrylonitrile as the carbon source. Successful composite formation was confirmed and textural properties were obtained from XRD, FTIR and Raman spectra studies. Morphological characterizations of the nanocomposite were investigated by FE-SEM and TEM measurements. For capacitive properties tests, cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy were carried out in a three-electrode system with a working potential window from 0 to 1 V. The results show that the membrane has a typical graphene-like layer carbon structure. Moreover, the electrochemical performance reveals that the average capacitance of the composite at the mass fraction of graphene-like membrane of 30 % is as high as 302 F g−1 at 1 A g−1 in 1 mol L−1 Na2SO4 electrolyte, which permit excellent performance as electrode materials for supercapacitors.

Traditional methods for the preparation of carbon aerogels, such as a sol–gel method, hydrothermal method, freeze-drying method and the direct carbonization of biomass materials, have been more and more limited in their applications due to their high cost, complex processes and the accompanying volume shrinkage in the preparation process. In this paper, we developed a novel air-expansion method for the preparation of porous carbonaceous aerogels with hierarchically macroporous, mesoporous and microporous structures from rice. The main advantages of an air-expansion method are large-scale preparation, low cost, a simple technique and most importantly it keeps the initial shape/structure and avoids shrinkage of the carbon aerogels owing to the air-expansion process of rice generating many macroporous structures for supporting the aerogel framework. When used as an anode for lithium ion batteries, rice-based carbonaceous aerogels exhibit a superior specific capacity and possess a good rate capability. This study gives a better insight into the preparation of carbonaceous aerogels from other grains as well as their potential applications in lithium ion batteries.

The widely used route of high-temperature pyrolysis for transformation of Prussian blue analogs (PBAs) to functional nanomaterials leads to the fast removal of CN- ligands, and thus the formation of large metal aggregates and the loss of porous structures inside PBAs. Here, a controllable pyrolysis route at low temperature is reported for retaining the confined effect of CN- ligands to metal cations during the whole pyrolysis process, thereby preparing high-surface-area cubes comprising disordered bimetallic oxides (i.e., Co3 O4 and Fe2 O3 ) nanoparticles. The disordered structure of Co3 O4 enables the exposure of abundant oxygen vacancies. Notably, for the first time, it is found that the in situ generated CoOOH during the oxygen evolution reaction (OER) can inherit the oxygen vacancies of pristine Co3 O4 (i.e., before OER), and such CoOOH with abundant oxygen vacancies adsorbs two - OH in the following Co3+ to Co4+ for markedly promoting OER. However, during the similar step, the ordered Co3 O4 with less oxygen vacancies only involves one - OH, resulting in the additional overpotentials for adsorbing - OH. Consequently, with high surface area and disordered Co3 O4 , the as-synthesized electrocatalysts have a low potential of 237 mV at 10 mA cm-2 , surpassing most of reported electrocatalysts.

Single-atom catalysts have great potential in electrochemical CO2 reduction reaction (CO2RR); however, plenty of single-atom sites are embedded inside without catalytic performance and most catalysts are powder-based with binding procedure, causing a relatively low current density. Herein, a strategy is proposed to maximize the utilization of single-atom cobalt sites via constructing a free-standing, cross-linked and high-yield carbon membrane (denoted as CoSA/HCNFs). The 3D net-like CoSA/HCNFs nanofibers with continuous porous structure can facilitate large electrochemical active surface areas and be in favor of the reactant transportation, which generate abundant effective cobalt single atoms for CO2 reduction. The highly utilization of single-atom Co sites eventually lead to CO with 91% Faradaic efficiency and 67 mA cm−2 current density in a typical H-type cell, 92% Faradaic efficiency as well as 211 mA cm−2 current density in a flow cell, respectively. This strategy for large-scale production of single-atom membranes could also be easily expanded to extensive electrolysis and energy storage devices.