Ongoing interest is focused on aqueous zinc ion batteries (ZIBs) for mass‐production energy storage systems as a result of their affordability, safety, and high energy density. Ensuring the stability of the electrode/electrolyte interface is of particular importance for prolonging the cycling ability to meet the practical requirements of rechargeable batteries. Zinc anodes exhibit poor cycle life and low coulombic efficiency, stemming from the severe dendrite growth, and irreversible byproducts such as H2 and inactive ZnO. Great efforts have recently been devoted to zinc anode protection for designing high‐performance ZIBs. However, the intrinsic origins of zinc plating/striping are poorly understood, which greatly delay its potential applications. Rather than focusing on battery metrics, this review delves deeply into the underlying science that triggers the deposition/dissolution of zinc ions. Furthermore, recent advances in modulating the zinc coordination environment, uniforming interfacial electric fields, and inducing zinc deposition are highlighted and summarized. Finally, perspectives and suggestions are provided for designing highly stable zinc anodes for the industrialization of the aqueous rechargeable ZIBs in the near future.
Electrochemical nitrogen reduction reaction (NRR) as a new strategy for synthesizing ammonia has attracted ever‐growing attention, due to its renewability, flexibility, and sustainability. However, the lack of efficient electrocatalysts has hampered the development of such reactions. Herein, a series of amorphous Sn/crystalline SnS2 (Sn/SnS2) nanosheets by an L‐cysteine‐based hydrothermal process, followed by in situ electrochemical reduction, are synthesized. The amount of reduced amorphous Sn can be adjusted by selecting electrolytes with different pH values. The optimized Sn/SnS2 catalyst can achieve a high ammonia yield of 23.8 µg h−1 mg−1, outperforming most reported noble‐metal NRR electrocatalysts. According to the electrochemical tests, the conversion of SnS2 to an amorphous Sn phase leads to the substantial increase of its catalytic activity, while the amorphous Sn is identified as the active phase. These results provide a guideline for a rational design of low‐cost and highly active Sn‐based catalysts thus paving a wider path for NRR.
Electrocatalysts are evolving toward chemically tunable atomic structures, among which the catalyst engineering from a defect perspective represents one of the mainstream technical genres. However, most defects cannot be purified or their numbers gauged, making them too complex to explore the hidden catalytic mechanism. A twin boundary, with well-defined symmetric structure and high electrocatalytic activity, is an elegant one-dimensional model catalyst in pursuing such studies. Here on polished Cu electrodes, we successfully synthesized a series of copper twin boundaries, whose density ranges from 0 to 10 5 cm −1 . The CH 4 turnover frequency on the twin boundary atoms is 3 orders higher than that on the plane atoms, and the local partial current density reaches 1294 mA cm −2 , with an intrinsic Faradaic efficiency of 92%. An intermediate experiment and density functional theory studies confirm the twin boundary's advantage in converting the absorbed CO* into CH 4 .
Transition-metal alloys have attracted a great deal of attention as an alternative to Pt-based catalysts for hydrogen evolution reaction (HER) in alkaline. Herein, a facile and convenient strategy to fabricate Co3Mo binary alloy nanoparticles nesting onto molybdenum oxide nanosheet arrays on nickel foam is developed. By modulating the annealing time and temperature, the Co3Mo alloy catalyst displays a superior HER performance. Owing to substantial active sites of nanoparticles on nanosheets as well as the intrinsic HER activity of Co3Mo alloy and no use of binders, the obtained catalyst requires an extremely low overpotential of only 68 mV at 10 mA cm–2 in alkaline, with a corresponding Tafel slope of 61 mV dec–1. At the same time, the catalyst demonstrates excellent stability during the long-term measurements. The density functional theory calculation provides a deeper insight into the HER mechanism, unveiling that the active sites on the Co3Mo-based catalyst are Mo atoms. This strategy of combining catalytic active species with hierarchical nanoscale materials can be extended to other applications and provides a candidate of nonnoble metal catalysts for practical electrochemical water splitting.
2D transition metal dichalcogenides (TMDs) have presented outstanding potential for efficient hydrogen evolution reaction (HER) to replace traditional noble metal catalysts. Here, to achieve enhanced HER performance, specific areas of the few-layer 1T′-MoTe 2 film are precisely controlled with a focused ion beam to create particular active sites. Electrochemical measurements indicate that the HER performance, although inconspicuous in pristine 1T′-MoTe 2 ultrathin films prepared through the chemical vapor deposition method, can be greatly enhanced after patterning and precisely controlled by the morphologies as well as the amounts of the defects, reaching a small onset potential and a record-low Tafel slope of 44 mV per decade for few-layer TMDs. Conductivity tests, visualized copper electrodeposition, and density functional theory calculations also confirm that the enhancement of HER performance comes from the exposed edges by patterning. In this pioneering work, not only is the catalysis mechanism of the edge active sites of 1T′-MoTe 2 unveiled, but also a universal route to study the properties of 2D materials is demonstrated.
Charge and mass transfer at the interface between electrode and electrolyte are of vital significance for energy conversion and storage in aqueous rechargeable zinc ion batteries (ZIBs). Approaching rational design and preparation of unique nanostructures with enhanced mass transfer is still facing great challenges in response to these problems. Herein, the highly uniform and round new‐state nsutite‐type vanadium dioxide (VO2) nanoplates with novel ancient Chinese coin structure (with thickness of ≈50 nm and diameter of ≈500 nm, with a hole in the middle) are prepared successfully. During the hydrothermal process, the VO2 nanoplate undergoes an interesting Ostwald ripening guided dissolution‐regrowth process, resulting in the formation of the unusual ancient Chinese coin structure. Impressively, based on structural merits of the abundant electrolyte‐accessible sites and transfer pathways, the mass transfer can be enhanced at the surface of as‐prepared VO2 nanoplates‐based electrode. The VO2 nanoplates further deliver high reversible specific capacity and rate ability for rechargeable ZIBs. Hence, this work presents a new avenue for designing unique nanostructure vanadium oxides to boost the electrochemical properties of aqueous ZIBs.
Catalyst doped with a single-atom noble metal displays distinctive catalytic behavior from the bulk counterparts, with tunable electronic structures and spatial versatilities, which excels in today's heterogeneous catalysis. To deposit noble metals in a single atomic level requires a restricted chemical environment and precise thermodynamic control. Electroplating methods are commercially used to deposit uniform and conformal metal thin films on different hardware surfaces. Yet the atomic level electroplating has never been achieved. Herein we demonstrate a voltage gauged electrochemical deposition method to synthesize single-atom Pt, Au, and Pd on MoS 2 and other two-dimensional (2D) materials. The surface atomic doping level for Pt, Au, and Pd can reach 1.1, 7.0, and 14%, respectively, and the doping sites are precisely positioned at Mo-and S-vacancies. The monodispersed noble atoms show enhanced hydrogen evolution activity and saturated CO tolerance, as explained by density functional theory calculations. CO 2 can also be electrochemically reduced into CO at a notable Faradaic efficiency of 4.56%.
Using vapor phase transformation to synthesize template‐directed metal–organic frameworks (MOFs) shows great promise as an approach to avoid the shortcomings of solution‐based strategies. However, among current research, either the products are confined to zeolitic imidazolate frameworks or the conversion technologies are limited to complex processes such as chemical vapor deposition. Here, a well‐designed sublimation‐vapor phase pseudomorphic transformation method is reported to fabricate vertically aligned nanosheet arrays of NiFe‐based MOFs with a uniform and controlled thickness, derived from NiFe‐layered double hydroxides. Benefiting from the optimized morphology and the high intrinsic activity originating from the synergistic coupling effect of NiFe metal clusters, the as‐prepared MOF electrocatalyst displays a superior oxygen evolution reaction performance, requiring an overpotential of 318 mV at 50 mA cm−2 with a Tafel slope of only 47 mV dec−1. Furthermore, a string of metal oxide‐MOFs are obtained, demonstrating the universality of this strategy. By observing the different stages of transformation, the transformation and growth mechanism of MOF crystals is unveiled for the first time. These findings may inspire the exploration and preparation of more species of MOFs, further broadening their application areas.
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