All solid-state lithium-sulfur batteries (ASSLSBs) are considered to be one of the most promising next-generation energy storage systems, due to the promises of high energy density and safety. Although the use of solid-state electrolytes could effectively suppress the "shuttle effect" and self-discharge of the conventional liquid lithium-sulfur (Li-S) battery, the commercialization of ASSLSBs has been seriously hampered by the electrolyte degradation, electrode/electrolyte interfacial deterioration, electrochemo-mechanical failure, lithium dendrite growth and electrode pulverization, etc. This paper provides a comprehensive review of recent research progresses on the solid-state electrolytes, sulfur-containing composite cathodes, lithium metal and lithium alloy anodes, and electrode/electrolyte interfaces in ASSLSBs. Specifically, lithium sulfide and metal sulfide as new active cathode materials, and lithium alloy as new anode materials are overviewed and analyzed. In addition, some newly developed interfacial modification strategies for addressing the electrode/electrolyte interfacial challenges are also outlined. Furthermore, an outlook on the future research and development of high-performance ASSLSBs are also presented.
The current or voltage fluctuation in fuel cell operation is harmful to the fuel cell system and power application equipment. Here, we report a technique to eliminate such a fluctuation by the aid of new type of catalysts, superlattice-like mesoporous PtCo catalysts. The current fluctuation in fuel cells catalyzed by two invented catalysts are fixed at as low as 25 mA·cm-2 with a power of 0.75 W·cm-2 or 120 mA·cm-2 with a power of 1.01 W·cm-2, and no noticeable current decay was detected over 100 h. By contrast, a cell catalyzed by conventional Pt/C catalysts with the same Pt loading delivered a current fluctuation as large as 180 mA·cm-2 even at low power output of 0.30 W·cm-2, which also showed 32% current decay rate in 50 h. The superlattices-like mesoporous structure not only enhances the mass transfer and depresses the water flooding but also effectively increases the Pt utilization within its 3D carbon frameworks. Its power output was as high as 11.69 W·mgPt-1 (MEA), which is 46.1% higher than the 2025 target of DOE, USA, 8.0 W·mgPt-1(MEA).
The electrochemical oxidation of C2H4 is attracting increasing attention due to its vast potential market. The current electrochemical methods rely on the use of redox mediators, which may produce corrosive intermediates, while direct oxidation is still limited by its low activity and selectivity. Herein, we conducted electrochemical studies to obtain mechanistic insights into the benchmark Pd catalyst. The generated Pd(II) could be the active site for C2H4 oxidation. By designing the pulse sequence, we found the ratio of strongly and weakly adsorbed C2H4 on Pd to be 0.3:1. The result we obtained provides a guideline for the rational design of high-performance C2H4 oxidation catalysts.
Metal nanomaterials have exhibited excellent performance in electrocatalytic applications, but they still face the problems of poor stability and limited regulation strategies. It is an efficient strategy for greatly enhanced catalytic activity and stability by introducing a second component. In this review, we provide the sketch for the combination of metal nanomaterials and cucurbit[n]urils (CB[n]s) in electrocatalytic applications. CB[n]s are a series of macrocycles with rigid structure, high stability, and function groups for coordinating with metal sites, which make them promising to stabilize and modulate the metal nanomaterials for ideal performance. The discussion classifies the roles of CB[n]s, involving CB[n]s as protecting agents, CB[n]-based supramolecular self-assemblies and CB[n]s as the precursor for the preparation of N-doped holy carbon matrix. Various metal nanocatalysts including metal (Pt, Ir, Pd, Ru, Au) nanoparticles, metal (Fe, Co, Ni) single-atoms, and transition metal carbides (TMCs) have been integrated with CB[n] or CB[n]-derived carbon matrix. These nanomaterials show superior activity and stability in multiple electrocatalytic reactions, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), methanol oxidation reaction (MOR), and ethanol oxidation reaction (EOR). Furthermore, a few metal-CB[n] composites can become bifunctional catalysts applied in the overall water splitting and fuel cell. It is surprising that the activity of CB[n]-based nanocatalysts is comparable with that of commercial catalyst, and the stability is even better. The experimental analysis together with the density functional theory (DFT) calculations verifies that the improvement can be attributed to the interaction between the metal nanocrystal and CB[n]s as well as the characteristic stability of CB[n]s. Finally, we talk about the challenges and opportunities for the cucurbit[n]uril-based electrocatalysis. This review provides an impressive strategy to obtain well-defined metal nanomaterials constructed with CB[n]s with enhanced performance, and expects that such a strategy will develop more efficient catalysts for a broader range of electro-applications.