ABSTRACT
It is critical and challenging to develop highly active and low cost bifunctional electrocatalysts for the hydrogen/oxygen evolution reaction (HER/OER) in water electrolysis. Herein, we propose cerium-vanadium-based hollow nanopillar arrays supported on nickel foam (CeV-HNA/NF) as bifunctional HER/OER electrocatalysts, which are prepared by etching the V metal-organic framework with Ce salt and then pyrolyzing. Etching results in multidimensional optimizations of electrocatalysts, covering substantial oxygen vacancies, optimized electronic configurations, and an open-type structure of hollow nanopillar arrays, which contribute to accelerating the charge transfer rate, regulating the adsorption energy of H/O-containing reaction intermediates, and fully exposing the active sites. The reconstruction of the electrocatalyst is also accelerated by Ce doping, which results in highly active hydroxy vanadium oxide interfaces. Therefore, extremely low overpotentials of 170 and 240 mV under a current density of 100 mA cm-2 are achieved for the HER and OER under alkaline conditions, respectively, with long-term stability for 300 h. An electrolysis cell with CeV-HNA/NF as both the cathode and anode delivers a small voltage of 1.53 V to achieve water electrolysis under 10 mA cm-2, accompanied by superior durability for 150 h. This design provides an innovative way to develop advanced bifunctional electrocatalysts for overall water electrolysis.
ABSTRACT
It is of significant importance to suppress the polysulfide shuttle effect for the commercial application of lithium-sulfur batteries. Herein, continuous MIL-101(Cr) membranes were successfully fabricated on carbon nanotube films utilizing a simplein situgrowth method, aiming at constructing interlayer materials for inhibiting the shuttle effect. Owing to the suitable pore aperture and super electrolyte wettability, the as-developed MIL-101(Cr) membrane can effectively inhibit the shuttle behaviour of polysulfides while allowing the fast transport of Li-ions simultaneously, working as an ionic sieve. Additionally, this MOFs membrane is also helpful in accelerating the polysulfide catalytic conversion. Therefore, the proposed interlayer delivers an extraordinary rate capability, showing a remarkable capacity of 661.9 mAh g-1under 5 C. Meanwhile, it also exhibits a high initial capacity of 816.1 mAh g-1at 1 C and an exceptional durability with an extremely low capacity fading of 0.046% per cycle over 500 cycles.
ABSTRACT
It is of significant importance to suppress the polysulfide shuttle effect for the commercial application of lithium-sulfur batteries. Herein, continuous MIL-101(Cr) membranes were successfully fabricated on carbon nanotube films utilizing a simple in-situ growth method, aiming at constructing interlayer materials for inhibiting the shuttle effect. Owing to the suitable pore aperture and super electrolyte wettability, the as-developed MIL-101(Cr) membrane can effectively inhibit the shuttle behaviour of polysulfides while allowing the fast transport of Li-ions simultaneously, working as an ionic sieve. Additionally, this MOFs membrane is also helpful in accelerating the polysulfide catalytic conversion. Therefore, the proposed interlayer delivers an extraordinary rate capability, showing a remarkable capacity of 661.9 mAh g-1 under 5 C. Meanwhile, it also exhibits a high initial capacity of 816.1 mAh g-1 at 1 C and an exceptional durability with an extremely low capacity fading of 0.046 % per cycle over 500 cycles.
ABSTRACT
Lithium-sulfur (Li-S) batteries possess many practical challenges including the lithium polysulfide (LiPS) "shuttle effect" and their sluggish conversion kinetics. To address these issues, a unique hierarchical porous architecture, combining highly conductive ordered macroporous skeleton and embedded microporous particles is rationally designed as a dual-effective polysulfide immobilizer and conversion promoter. In this nanoporous architecture, Al-doped ZnO (AZO) acts as a conductive macroporous framework, profiting chemical anchoring of LiPS as well as facilitating electrolyte infiltration and ion diffusion; Co nanoparticle-anchored N-doped carbon (Co-NC) derived from CoZn-metal-organic framework is embedded in the macropores to further strengthen the LiPS adsorption, catalytically accelerating conversion kinetics of LiPS simultaneously. Consequently, the Co-NC@AZO/S cathode delivers a notable rate capability of 635.5 mA h g-1 at 5 C. A high area capacity of about 5.8 mA h cm-2 with a mass loading of 6.8 mg cm-2 is also achieved under a lean electrolyte (E/S = 5.7). Additionally, the Li-S pouch cells equipped with Co-NC@AZO can be extended to sulfur loading as high as 4.0 mg cm-2, delivering a superb capability of 897.5 mA h g-1 after 100 cycles. This work puts forward a design for stably cycled and practically viable Li-S batteries.
ABSTRACT
Restraining the shuttle effect in lithium-sulfur (Li-S) battery is crucial to realize its practical application. In this work, a UiO-66@carbon (UiO-66@CC) interlayer was developed for Li-S battery by growing a continuous UiO-66 film on carbon cloth. The continuous UiO-66 crystal layer contributes to provide sufficient adsorptive and catalytic sites for efficient adsorption and catalytic conversion towards polysulfides. Moreover, the hydrophilic property of UiO-66 material ensures the full infiltration of electrolyte and accelerates the transportation of lithium ions. Profiting from the above advantages of the proposed interlayer, the shuttle effect is effectively inhibited and a fast redox kinetic is also realized. Accordingly, the Li-S battery using UiO-66@CC delivers a specific capacity of 1228.9 mAh g-1at 0.2 C with a nearly 100% capacity retention after 100 cycles, and the first specific capacity is 1033.1 mAh g-1at 1.0 C with a decay rate of 0.07% over 600 cycles. Meanwhile, UiO-66@CC interlayer also has an excellent rate performance with a specific capacity of 535.9 mAh g-1at 5.0 C and a high area capacity of 6.2 mAh cm-2at increased sulfur loading (8.15 mg cm-2).
