Short-Range Nanoreaction Effect on the Hydrogen Desorption Behaviors of the MgH₂–Ni@C Composite

Abstract

Doping a catalyst can efficiently improve the hydrogen reaction kinetics of MgH2. However, the hydrogen desorption behaviors are complicated in different MgH2–catalyst systems. Here, a carbon-encapsulated nickel (Ni@C) core–shell catalyst is synthesized to improve the hydrogen storage properties of MgH2. The complicated hydrogen desorption mechanism of the MgH2–Ni@C composite is elucidated. The experimental and theoretical calculation results indicate a short-range nanoreaction effect on the hydrogen desorption behaviors of the MgH2–Ni@C composite. The Ni@C catalysts and the adjacent MgH2 form nanoreaction sites along with preferential hydrogen desorption. The new interface between the in situ formed Mg and residual MgH2 contributes to the subsequent hydrogen desorption. With the nanoreaction sites increased via adding more catalyst, the short-range nanoreaction effect is more prominent; as a comparison, the interface effect becomes weaker or even disappears. In addition, the core–shell structure catalyst shows ultrahigh structural stability and catalytic activity, even after 50 hydrogen absorption and desorption cycles. Hence, this study provides new insights into the complicated hydrogen desorption behaviors and comes up with the short-range nanoreaction effect in the MgH2–catalyst system.

Engineering the Electronic Interaction between Atomically Dispersed Fe and RuO2 Attaining High Catalytic Activity and Durability Catalyst for Li‐O2 Battery

“…DFT calculation was performed to deeply explore the source of the superior catalytic activity of Fe SA ‐RuO 2 /HPCS cathode. Since the physical and chemical properties of cathode materials (HPCS) used in this work were basically consistent with previous work, [ 31,32 ] and the electrochemical properties and discharge products of LOBs based HPCS cathodes are also very close to our previous work, [ 32 ] only catalytic components loaded on HPCS were considered. Hence, to simulate the active sites of Fe 2 O 3 /HPCS, RuO 2 /HPCS and Fe SA ‐RuO 2 /HPCS cathodes in LOBs, three models (Fe 2 O 3 , RuO 2 , and Ru‐O‐Fe 1 ) were established.…”

“…First, HPCS derived from sodium citrate is used as the substrate carbon material. According to our previous reports, [ 31,32 ] as the cathode of Li‐O 2 or Li‐CO 2 batteries, HPCS have advantages such as hollow spherical shell with thin shell, abundant pore and 3D cross‐linking structure, which can provide a large number of fast channels for gas/ions and have enough space to store discharge products. Subsequently, HPCS supported Ru NPs are prepared by liquid‐phase reduction method, and a small amount of Fe(acac) 3 is added to deposit atomically dispersed Fe species on the surface of Ru NPs (FeRu NPs/HPCS).…”

“…All the samples show semi‐open spherical shell morphology with very thin shells (≈10 nm) and cross‐linking with each other, and the sizes of these spherical shells range from tens to hundreds of nanometers, which are typical morphological characteristics of HPCS. [ 31–33 ] It is worth mentioning that the spherical shell surfaces on all samples are relatively smooth and no significant nanoparticles are observed, suggesting that the loaded nanoparticles should be very fine. [ 25 ] To analyze NPs on these samples, they are observed by using transmission electron microscopy (TEM).…”

“…The phases of the samples are identified by the XRD and Raman technique. The XRD pattern presents a broad humps peak at 25° and an inconspicuous peak locates at 43°, corresponding to the graphitic (002) and (100) planes, [ 31–33 ] respectively, which indicates the amorphous state of HPCS (Figure S5, Supporting Information). No other diffraction peaks are observed in the remaining samples, which may be due to the poor crystallinity of HPCS and the fine NPs in these samples.…”

Insights into an Amorphous NiCoB Nanoparticle-Catalyzed MgH2 System for Hydrogen Storage

“…Hydrogen energy with high mass-energy density and nonpollution combustion products is conducive to liberate the energy dependence on fossil fuels and provide creativity for green energy development. 1,2 Hydrogen storage technology occupies an important position in the hydrogen energy industry. 3,4 The current hydrogen storage methods are mainly divided into high-pressure gaseous storage, hypothermal liquid storage, and solid-state storage.…”