High-entropy oxides (HEOs) are promising electrocatalysts for the sluggish oxygen evolution reaction (OER). The lattice oxygen mechanism (LOM) offers a lower thermodynamic barrier than the conventional adsorbate evolution mechanism (AEM). However, maintaining structural integrity while activating lattice oxygen during prolonged electrolysis remains a significant challenge. Herein, we report a dual sacrificial template strategy to synthesize single-crystalline porous hollow high-entropy ZnVCrMoMn spinel oxides (ZnVCrMoMn-HHESOs). Chemical probe, in situ spectroscopic, and isotope-labeling experiments demonstrate that multicomponent electronic interactions synergistically enhance lattice oxygen activation and promote a dominant LOM pathway with high structural stability. Density functional theory calculations reveal that high-valent cation incorporation induces electron redistribution, upshifts the O 2p-band center toward the Fermi level, and strengthens metal-oxygen covalency, facilitating lattice oxygen participation in the OER. Consequently, ZnVCrMoMn-HHESOs delivers an ultralow overpotential of 218 mV at 10 mA & centerdot;cm-2 and outstanding stability over 400 h. In a lab-scale electrolyzer, it achieves 774 mA & centerdot;cm-2 at 1.7 V and operates stably at 500 mA & centerdot;cm-2 for over 500 h with a voltage degradation rate of merely 0.07 mV & centerdot;h-1. This work demonstrates the rational design of hollow high-entropy spinel oxides as an effective strategy for developing highly active and stable LOM-based OER electrocatalysts.

Battery packaging capable of autonomous temperature regulation is a highly attractive strategy for thermal management systems, as it directly enhances safety by mitigating thermal runaway risks. In this work, an...

Metal-organic frameworks (MOFs) have become promising platforms for designing functional heterogeneous catalysts. However, the predominant method entails carbonization to generate porous carbon materials, a process that unavoidably leads to the forfeiture of their inherent MOF properties. Herein, we engineered a partially regulated pyrolysis technique to synthesize ZIF-67 with partially removed ligands (p-ZIF-67) embedded within Cu2S nanorods (NR) for the electrochemical oxygen evolution reaction (OER). Notably, under 95 % iRcompensated conditions, the optimized p-ZIF-67@Cu2S NR electrode achieves exceptional performance with a current density of 50 mA cm-2 at an overpotential of 277 mV. Compared to the non-pyrolyzed ZIF-67@Cu2S, the enhanced electrocatalytic activity originates from the abundant heterogeneous interfaces formed by the preserved MOF structure and newly generated p-ZIF-67 nanoparticles. In-situ electrochemical impedance spectroscopy and Raman spectroscopy reveal that this heterointerface engineering facilitates efficient charge transfer, full exposure of active sites, and accelerated mass transport during catalysis, thereby markedly enhancing OER performance. This study presents a viable approach for developing cost-effective and high-performance MOFderived electrocatalysts through the application of nanointerface engineering strategy.

In lithium-sulfur batteries (LSBs), sulfur-rich copolymers have attracted wide attention due to the reduced dissolution of active material and alleviated self-discharge problem through the efficient chemical interaction between polysulfide and carbon. Herein, we present an effective strategy to encapsulate sulfur-rich copolymer into NiCo2S4 encapsulated hierarchical porous N/O dual-doped graphitic carbon nanocages (GCNs), named S-DIB@NiCo2S4@PDA@rGO-GCNs. The host NiCo2S4@PDA@rGO-GCNs matrix can not only provide the “lithiophilic”-rich polar sites and tight anchored LiPSn on the N/O dual-doped GCNs surface, and “sulfphilic” NiCo2S4 electrocatalyst for accelerated sulfur electrochemistry, but also offer abundant hierarchical pores for accommodating sulfur and cushioning its volume expansion. Both of the experimental and theoretical analyses reveal the S-DIB@NiCo2S4@PDA@rGO-GCNs possesses the strong chemisorptions and catalytic ability with the synergetic mechanism, suppressing the self-discharge problem. As a proof-of-concept study, the assembled LSBs cells show excellent discharge capacities of 486 and 324 mA h g−1 at 5C and 10 C after 1000 cycles, respectively. The corresponding capacity loss rate is as low as 0.032 % and 0.030 % per cycle, respectively. Thanks to the exceptional lithiophilic and sulfiphilic characteristic, the LSBs pouch cell also demonstrates high cycling stability. The proposed hierarchical encapsulation strategy with synergetic chemisorptions and catalytic ability shows great potential for developing advanced electrodes for next-generation high-performance rechargeable batteries.

Noble metal-free electrocatalysts for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are crucial to rechargeable metal-air batteries. Nanoporous high-entropy spinels have recently been studied as bifunctional ORR/OER electrocatalysts due to the adjustable surface electronic structure and catalytic activity. In this work, we adjust catalytic activities of HEO by varying the composition and proportion of the metal elements and find an optimal seven-component AlNiCoFeCrMoV prepared by a scalable two-step dealloying strategy. The seven-component HEO is highly active for OER while it exhibits a relatively poor ORR activity, much worse than the commercial Pt/C. Thus, the highly ORR active Co-N-C is rationally integrated with the seven-component HEO to construct a highly bifunctional HEO/Co-N-C nanocomposite electrocatalyst. Importantly, when used in a Zn-air battery, small charge/discharge voltage differences and ultralong lifespan (at 2, 5, 10 mA cm-2) can be achieved. This work highlights the rapid screening and rational design of highly bifunctional catalysts by function integration in multicomponent high-entropy system.

High-entropy materials are new-fashioned electrocatalysts due to their interesting "cocktail effect". However, it is still a great challenge to synthesize single-crystal high-entropy nanomaterials such as (oxy)hydroxides due to the different crystal growth mode for different elements. Herein, we design a dynamic crystal growth strategy by multi-cation exchange to fabricate single-crystal high-entropy (oxy)hydroxides nanosheets. Nanoporous morphology can be achieved by incorporating Al ion into the multicomponent (oxy)hydroxides system after a reversible Al insertion-dissolution process. When adopted as potential electrocatalysts for oxygen evolution reaction (OER), we find that the seven-component ZnVNiCoFeAlRu-OHs single-crystal nanoporous nanosheets display a significantly improved OER performance with a low overpotential of 229 mV at 10 mA cm-2 and a shallow Tafel slope of 39.3 mV dec � 1. Both XPS and DFT calculation reveal that Ru acted an electron dedicator could effectively moderate the overall electronic structures for better OER performance. This work develops an entropy and enthalpy driven multi-cation exchange strategy for synthesizing a library of single-crystal highentropy (oxy)hydroxides for various applications.

High-entropy materials (HEMs) are new-fashioned functional materials in the field of catalysis owing to their large designing space, tunable electronic structure, interesting "cocktail effect", and entropy stabilization effect. Many effective strategies have been developed to design advanced catalysts for various important reactions. Herein, we firstly review effective strategies developed so far for optimizing HEM-based catalysts and the underlying mechanism revealed by both theoretical simulations and experimental aspects. In light of this overview, we subsequently present some perspectives about the development of HEM-based catalysts and provide some serviceable guidelines and/or inspiration for further studying multicomponent catalysts.

Flexible transparent conductive films are gaining attention day by day over the last few years due to it is a key component of next generation flexible electronics and optoelectronic devices. Indium tin oxide (ITO) as one of the most widely used transparent conductive material is limited by the traditional deposition approach cannot be achieve ultra-thin, which results in its brittle nature. Herein, a novel strategy for fabricating highly transparent conductive films by liquid metal interface phase separation technique based on low-melting liquid metal of InxSn100-x alloy is reported, during the solid-to-liquid phase transition of alloy, the monolayer of surface oxide film segregated with the bulk phase and was printed on the flexible polyethylene-naphthalate (PEN) substrate under the van der Waals. This novel strategy can directly print the ultra-thin self-oxide with the structure of ITO on PEN substrate, with the resulting of transparency over 97.5% and resistivity as low as 0.21 kΩ cm, providing a new way of low-cost raw ITO material as well as the personalized preparation strategy. The desirable highly transparent conductive films are comparable to recently reported ITO film, together with advantages of pretty steady, make them attractive as various flexible transparent conductive electrodes, for example, an ultra-thin ITO film is developed for luminescent devices.

The catalytic activity and durability of RuO2 clusters toward the oxygen evolution reaction (OER) are strongly associated with their support; however, how the electronic interaction would enhance the catalytic performance is still not quite clear. Herein, hierarchical nanoporous and single-crystal Zn3V3O8 nanosheets are adopted to anchor in situ formed RuO2 clusters. X-ray photoelectron analysis reveals significant binding energy changes of both Ru and V due to the creation of strong Ru-O-V bonding interaction, which would lead to the reconstruction of the electronic structure of the Zn3V3O8 matrix and RuO2 clusters. The ultrastrong electronic interaction also results in superior OER activity, indicated by a small overpotential at 10 mA cm-2 (228 mV) and a shallow Tafel slope of 46 mV dec-1. First-principles simulation further reveals the synergistic effect derived from the unique RuO2@Zn3V3O8 couple, which effectively regulates the electronic structure for the OER process. In addition, the created interfacial chemical bond and the confined microporous structure of the Zn3V3O8 substrate could prevent the RuO2 clusters from detachment and aggregation, making the nanocomposite a promising long-term stable OER electrocatalyst.

Alkaline anion exchange membrane (AEM) water electrolysis is currently the most promising hydrogen production technology, and the development of non-precious metal-based hydrogen evolution reaction (HER) electrocatalysts with high performance and low price is one of the greatest challenges for large-scale AEM. Although the reaction mechanism of HER under alkaline conditions is very different from acidic conditions, many researchers still believe that the HER activity is determined by Gibbs free energy for hydrogen absorption (Delta G(H*)) in all pH environments. In the meantime, vanadium-based nitrides are rarely reported as alkaline HER catalysts due to the large density unoccupied orbitals of V cause high Delta G(H*) value. Herein, we prepare nanoporous VN sheet arrays (NSAs) with high specific surface by hydrothermal-nitriding treatment, and then optimize its electronic structure via varying the doping amount of Co. As a result, the Co doped VN NSAs display an outstanding HER performance (overpotential of 37 mV at 10 mA cm(-2) and Tafel slope of 41 mV dec(-1)), which is even close to the commercial Pt/C catalyst under alkaline conditions. Moreover, by combining theoretical calculations and HER performances under acid and basic conditions, we find that the adsorption/desorption of hydrogen on activity sites could not fully revealed by Delta G(H*). This work opens up a new door to understand the mechanism of alkaline HER reaction and the development of HER electrocatalysts.

Developing stable and cost-effective catalysts is the key to the next-generation renewable energy conversion technology. Here we unify computational and experimental approaches to use the Zn3V3O8 (001) surface supporting noble metal Ru as a bifunctional catalyst for the OER and HER in alkaline media. In particular, different reaction sites have been studied at four surface terminations along the [001] orientation: the A-layer with V atoms at octahedral sites, the C-layer with V and Zn atoms at octahedral sites, and with additional Zn atoms at tetrahedral sites (B-layer and D-layer, respectively). The first-principles density functional theory (DFT) results indicate that the B-layer termination with V and tetrahedrally coordinated Zn on the top showed the best OER catalytic effect, while the HER favored the D-layer termination with extra Zn atoms at the octahedral sites on the top layer. Our DFT results also suggest that Ru doping by substituting V and Zn atoms at the octahedral site could dramatically enhance the catalytic activities for the OER and HER, respectively. In particular, compared to undoped Zn3V3O8, Ru doping could reduce the calculated OER overpotential from 0.58 V to 0.30 V, which has been confirmed by our experimental results that the OER overpotential decreased from 480 mV to 260 mV at a current density of 10 mA cm-o. Moreover, the experimental results show that Ru doping could reduce the HER overpotential from 152 mV to 70 mV at a current density of 10 mA cm-r. The new insights into the underlying catalytic mechanisms may be further extended to many similar electrocatalytic processes.

The instability and low activity of WO3 is the hot-topic for photoelectrochemical (PEC) water splitting, which is decreased by a sluggish interfacial kinetics and incomplete water oxidation. Aiming at such issues, we designed a ternary WO3/RG/Ni:FeOOH photoanode, which exhibits 2.05 times larger photocurrent (1.32 mA cm(-2)) than the WO(3)NFs in 0.5 M Na2SO4 electrolyte solution, accompanied with 83 mV cathodic shift of onset potential. These results demonstrates PEC response can occurs only in Ni:FeOOH but not FeOOH. Therefore, Ni:FeOOH acting as bi-functional modifier, can not only increase light absorption but also promote charge transfer process by forming p-n heterojunction with the WO(3)NFs. Besides, RGO forming a continuously conducting network can further improve charge separation process. Owing to their synergistic effects, the Faradaic efficiency and stability are both improved compared to its counterparts and the bare WO(3)NFs. This work may inspire the PEC application in other co-catalyst decorated systems.

Exploring low-cost bifunctional electrocatalysts for efficient water splitting still faces arduous challenges. Herein, a general and straightforward method is developed to prepare 3D hierarchical nanoporous V2O3 nanosheets anchored with different alloy nanoparticles by adopting metal-ion-doped zinc-vanadium (oxy)hydroxides as precursors. To demonstrate this concept, we produced nanoporous V2O3 nanosheets dotted with NiFe alloy nanoparticles through high-temperature reduction and free corrosion. Due to the increased number of active sites, accelerated mass transfer originating from the designed nanoporous architecture, and the metallic property of the V2O3 matrix, the NiFe@V2O3 hybrid exhibits excellent electrocatalytic performances for both oxygen and hydrogen evolution reactions. When adopting the NiFe@V2O3 as a bifunctional electrode for overall water splitting, it only requires a cell voltage of 1.56 V to reach 10 mA cm-2. This work provides a general and practical way to prepare high-efficient and low-cost electrocatalysts.

In article number 1800575, Xiao Gu, Yu Wang, and co-workers report a novel platinum-like, double-deck carbon coated V8C7 network with the highly active (110) facet exposed, as an efficient hydrogen evolution reaction (HER) electrocatalyst in the whole range of pH. Electrochemical tests and theoretical simulation indicate that the metallic character of V8C7, high-activity of exposed facet, and low barrier energy for water dissociation contribute to the catalytic activity.

Two-dimensional sandwich-like Co/C samples with a series of different thicknesses of Pt layers have been developed for oxygen reduction reaction.

In the past decade, fossil fuel resources have been exploited and utilized extensively, which could lead to increasing environmental crises, like greenhouse effect, water pollution, etc. Accordingly, many coping strategies have been put forward, such as water electrolysis, metal-air batteries, fuel cell, etc. Among the strategies mentioned above, water electrolysis is one of the most promising. Water splitting, which can achieve sustainable hydrogen production, is a favorable strategy due to the abundance of water resources. Splitting of water includes two half reactions integral to its operation: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, its practical application is mainly impeded by the sluggish anode reaction. Simultaneously, noble metal oxides (IrO2 and RuO2) and Pt-based catalysts have been recognized as typical OER catalysts; however, the scarcity of noble metals greatly limits their development. Hence, designing an alternative electrocatalyst plays a vital role in the development of OER. However, exploring a highly active electrocatalyst for OER is still difficult. Herein, a miraculous construction of a tree-like array of NiS/Ni3S2 heterostructure, which is directly grown on Ni foam substrate, is synthesized via one-step hydrothermal process. Since NiS and Ni3S2 have shown great OER performance in previous investigations, this novel NiS-Ni3S2/Nikel foam (NF) heterostructure array has tremendous potential as a practical OER catalyst. Upon application in OER, the NiS-Ni3S2/NF heterostructure array catalyst exhibits excellent activity and stability. More specifically, this novel tree-like NiS-Ni3S2 heterostructure array shows extremely low overpotential (269 mV to achieve a current density of 10 mAcm(-2)) and small Tafel slope for OER. It also shows extraordinary stability in alkaline electrolytes. Compared with the Ni3S2 nanorods array, the NiS-Ni3S2 heterostructure array has a synergistic effect that can improve the OER performance. Due to the secondary structure (Ni3S2 nanosheets), the tree-like NiS-Ni3S2 array provides more active sites could have higher specific surface area. The greater activity of the NiS/Ni3S2 heterostructure may also stem from the tight conjunction between tree-like NiS/Ni3S2 and the Ni foam substrate, which is beneficial for electronic transmission. Hydroxy groups can accumulate in large amounts on the surface of the tree-like array, and it also generates some Ni-based oxides that are favorable to OER. Moreover, the synergistic effect of such heterostructure can intrinsically improve the OER activity. The unique tree-like NiS-Ni3S2 heterostructure array has great potential as an alternative OER electrocatalyst.

Exploring low‐cost hydrogen evolution reaction (HER) catalysts with remarkable activity over wide pH range (0–14) still remains an enormous challenge. Herein, for the first time, a novel platinum‐like, double‐deck carbon coated V8C7 networks with the highly active (110) facet exposed as a new efficient HER electrocatalyst is reported. The single‐crystal interweaved V8C7 networks are designed and fabricated based on a low crystal‐mismatch strategy and confinement effect of double‐deck carbon coating. In addition, electrochemical tests and theoretical simulation indicate that the metallic character of V8C7, high‐activity of exposed facet, and low barrier energy for water dissociation can contribute to highly catalytic activity of HER. Impressively, the HER performances of the interweaved V8C7 networks can be comparable to those of Pt at an all‐pH environment, with Tafel slopes of 44, 64, and 34.5 mV dec−1and overpotential of 47, 77, and 38 mV at −10 mA cm−2 in 1 m KOH, 0.1 m phosphate buffer, and 0.5 m H2SO4, respectively. This work provides a blueprint for exploring new‐type platinum‐like catalysts for various energy conversion systems.

Understanding and designing versatile electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolyte is of great interest and importance towards overall water splitting. Here we investigated the crystal-plane-dependent electrocatalytic activity of NiCo2O4 crystals by combining experimental studies and theoretical calculations for the first time. It is revealed that NiCo2O4 nanosheet exposing {1 1 0} crystal planes shows higher catalytic activity for both HER and OER than that of NiCo2O4 octahedron exposing {1 1 1} crystal planes and NiCo2O4 truncated octahedron exposing {1 1 1} and {1 0 0} crystal planes. Furthermore, we grew the nanosheet with {1 1 0} planes on nickel foam (NF), which could guarantee fast electron and ion transport, rapid release of evolved bubbles and good structural stability, leading to the improved electrochemical performance. Acting as both anode and cathode electrocatalysts with a two-electrode electrolyzer in alkaline medium, NiCo2O4 nanosheet array produced a small cell voltage of 1.59 V to drive a current density of 10 mA cm(-2). The research presented here is of both fundamental and instructional significance because it unveils that selectively exposing specific crystal planes is very effective to receive promising catalysts for overall water splitting. (C) 2017 Elsevier Inc. All rights reserved.

During the past few decades, substantial efforts have been made to explore high-performance electrocatalysts for proton-exchange membrane fuel cells due to the sluggish oxygen reduction reaction kinetics at the cathode. Among multifarious approaches, it has been demonstrated that alloying Pt nanocrystals with transition metals and introducing Pt-based nanocrystals with high-index facets have been recognized as effective strategies to facilitate the enhancement of oxygen reduction reaction performance. However, the current synthetic approach for preparing catalysts with high-index facets is complicated. Herein, we demonstrate a straightforward one-step method to synthesize three-dimensional flower-like high-index faceted PtNi alloy nanocrystals constituted by abundant nano-cones similar to the quadrihedron. The as-prepared catalyst exhibits remarkably improved catalytic performance in comparison with PtNi-1, PtNi-2 and Pt/C, which is ascribed to a great number of high-index facets and highly open hierarchical structure. The resultant high-index faceted PtNi alloy nanocrystals deliver excellent mass activity of 1.76 Amg(-1). Meanwhile, the material also displays a great stability after 20000 potential cycles. Consequently, the methodology proposed in this work may provide some guidance to boost the improvement of oxygen reduction reaction, and the 3D flower-like high-index faceted PtNi alloy nanocrystals have a great potential to be turned into effective cathode catalysts for proton-exchange membrane fuel cells. (c) 2018 Elsevier Ltd. All rights reserved.