Abstract Solid‐state storage of hydrogen molecules in carbon‐based light metal single‐atom materials is promising to achieve both high hydrogen storage capacity and uptake rate, but there is a lack of fundamental understanding and design principles to guide the rational design of the materials. Here, a theoretical relationship is established between the hydrogen capacity/rate and the structures of the heteroatom‐doped‐graphene‐supported light metal Li single atom materials for high‐efficient solid‐state hydrogen storage, which is verified by combining spectroscopic characterization, H 2 adsorption/desorption measurements, and density functional theory (DFT) calculations. Based on the DFT calculations, a novel descriptor Φ is developed to correlate the inherent properties of dopants with the hydrogen storage properties, and further to screen out the best dual‐doped‐graphene‐supported light metal Li single‐atom hydrogen storage materials. The dual‐doped materials have a much higher hydrogen storage capability than the sole‐doped ones and exceed the best carbon‐based hydrogen storage materials so far.
Abstract A highly reversible zinc anode is crucial for the commercialization of zinc‐ion batteries. However, the change in the microstructure of the electric double layer originated from the dynamic change in charge density on the electrode greatly impacts anode reversibility during charge/discharge, which is rarely considered in previous research. Herein, the zwitterion additive is employed to create an adaptive interface by coupling the transient zwitterion dynamics upon the change of interfacial charge density. Ab initio molecular dynamics simulations suggest the molecular orientation and adsorption groups of zwitterions will be determined by the charging state of the electrode. ZnSO 4 electrolyte with zwitterion fulfills a highly reversible Zn anode with an average Coulombic efficiency of up to 99.85%. Zn/Zn symmetric cells achieve greatly enhanced cycling stability for 700 h with extremely small voltage hysteresis of 29 mV under 5 mA cm −2 with 5 mAh cm −2 . This study validates the adaptive interface based on transient dynamics of zwitterions, which sheds new light on developing highly reversible metal anodes with a high utilization rate.
Abstract Developing non‐platinum group metal (non‐PGM) electrocatalysts for the hydrogen oxidation reaction (HOR) represents the efforts towards the more economical use of hydrogen fuel cells and hydrogen energy, which has attracted tremendous attention recently. However, non‐PGM electrocatalysts for the HOR are still in their early development stages as compared with the significant advances in those for the oxygen reduction reaction and hydrogen evolution reaction. Herein, this paper summarizes the recent progresses and highlights the key challenges for the rational design of non‐PGM electrocatalysts, aiming to promote the development of non‐PGM HOR electrocatalysts. Fundamental understandings of the HOR mechanism are firstly reviewed, where theoretical interpretations on the low HOR kinetics in alkaline media, including the hydrogen binding energy theory, the bifunctional mechanism, and the water molecule reorganization, are particularly discussed. Subsequently, progresses of typical non‐PGM HOR electrocatalysts in acid and alkaline media are summarized separately. For the HOR under alkaline conditions, the superiorities and challenges of Ni‐based catalysts are discussed with a particular focus as they are the most promising non‐PGM electrocatalysts. Finally, this paper highlights the challenges and provide perspectives on the future development directions of non‐PGM HOR electrocatalysts.
A synergetic effect of K, Ti and F together on improving the reversible hydrogen storage properties of NaAlH(4) is found by intruding K(2)TiF(6) as catalyst precursor. Around 4.4 wt% of hydrogen can be released from the NaAlH(4)-0.025 K(2)TiF(6) sample within 40 min at 140 °C.
Lithium borohydride (LiBH4), with a high hydrogen capacity of 18.5 wt %, is an ideal candidate for hydrogen storage; however, it suffers from high thermal stability, low kinetics, and poor reversibility. Nanoconfinement is an effective strategy to tackle these problems, but a main drawback of nanoconfined systems is the low loading fraction of LiBH4, which leads to a low theoretical hydrogen capacity of the systems. It is thus highly desired to design scaffolds with high porosity and a reasonable pore structure for achieving high loading of LiBH4. In this work, porous hollow carbon nanospheres (PHCNSs) with uniform size, high specific surface area, large pore volume, and reasonable pore structure are delicately designed and controllably synthesized as the scaffold for confining LiBH4. The as-prepared PHCNSs can accommodate up to 70 wt % LiBH4, while the system still shows a low dehydrogenation temperature of ca. 200 °C and releases rapidly 8.1 wt % H2 at 350 °C within 25 min. Such a high loading of LiBH4 and high dehydrogenation capacity at a low temperature have never been reported to date based on our knowledge of carbon-based nanoconfined LiBH4 systems. Moreover, the system with 60 wt % LiBH4 shows favorable reversibility and rapid hydrogenation under moderate conditions. The morphology and structure evolutions of the confined systems during cycling are investigated, and the mechanism of the improved hydrogen storage property is proposed. The present work provides further insight into rationally utilizing porous carbon scaffolds with a well-designed structure to improve the hydrogen storage performance of LiBH4.
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