Abstract Rechargeable aqueous Zn ion batteries (AZIBs) have attracted significant attention as a promising alternative to Li‐ion batteries due to the use of water‐based electrolytes, high energy ...density per volume, and cost‐effectiveness. However, various parasitic reactions relating to hydrogen evolution reaction, corrosion, and dendrite growth in the Zn anode can result in the degradation of the electrochemical performance of AZIBs. Therefore, understanding the mechanisms underlying these various phenomena and their role in the electrochemical performance of AZIBs provides valuable insights for the development of anode and cathode materials. In this study, we investigate the effect of the MnO 2 cathode and Al 2 O 3 ‐coated Zn anode on the electrochemical performance of the AZIBs. The experimental results show that Al 2 O 3 ‐coated Zn anodes efficiently suppress the dendrite growth on the Zn. However, significant cycling fade of the full cell comprising of an Al 2 O 3 ‐coated Zn anode and MnO 2 cathode was observed during continuous charge/discharge cycles. The poor cycle performance can be mainly attributed to the phase transformation of MnO 2 –Mn 2 O 3 and the formation of various byproducts, which highlights the importance of the electrochemical stability of cathode materials in AZIBs to improve the cycle performance.
Understanding interfaces between dissimilar materials is crucial to the development of modern technologies, for example, semiconductor–dielectric and thermoelectric–semiconductor interfaces in ...emerging electronic devices. However, the structural characterization of buried interfaces is challenging because many measurement techniques are surface sensitive by design. When interested in interface evolution during synthesis, the experimental challenges multiply and often necessitate in situ techniques. For solution‐derived lead zirconate titanate (PZT) ferroelectric thin films, the evolution of buried interfaces during synthesis (including dielectric–metal and metal–metal) is thought to dramatically influence the resultant dielectric and ferroelectric properties. In the present work, multiple experimental and computational methods are combined to characterize interface evolution during synthesis of ferroelectric PZT films on platinized Si wafers—including in situ X‐ray diffraction during thermal treatment, aberration‐corrected scanning transmission electron microscopy of samples quenched from various synthesis states, and calculations using density functional theory. Substantial interactions at buried interfaces in the PZT/Pt/Ti/SiO
x
/Si heterostructure are observed and discussed relative to their role(s) in the synthesis process. The results prove that perovskite PZT nucleates directly from the platinum (111)‐oriented bottom electrode and reveal the roles of Pb and O diffusion and intermetallic Pt3Pb and Pt3Ti phases.
The evolution of buried interfaces during crystallization of ferroelectric lead zirconate titanate thin films on platinum electrodes is studied using multiple experimental and computational techniques. Temporal and spatial analysis of chemistry and structure (such as that illustrated in the figure) is used to reveal the roles of various mechanisms in film evolution.
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•Sulfidation performed on these homogeneously grown nanosheets (NiFe-LDH-S) via a facile CVD process.•Optimal NiFe-LDH-S sample demonstrated excellent catalytic activity.•NiFe-LDH-S ...showed high corrosion resistance for seawater oxidation.•Synthesized NiFe-LDH-S350 exhibited enhanced intrinsic catalytic activity metrics.
Given the abundance of water on the surface of the Earth, water splitting using seawater may be an effective solution to the future energy crisis. However, oxygen evolution reaction (OER) electrocatalysts require several specific characteristics to be used in seawater electrolysis, such as high catalytic activity, selectivity, and resistivity against chlorine corrosion. This paper reports that sulfur incorporation into nickel–iron layered double hydroxide (NiFe-LDH-S) can fulfill the abovementioned requirements for seawater oxidation. Sulfidation was performed on NiFe-LDH nanosheets homogeneously grown on a porous carbon scaffold via a facile chemical vapor deposition (CVD) process. The best NiFe-LDH-S sample demonstrated excellent catalytic activity with a high corrosion resistance for seawater oxidation.
Poly-(dimethylsiloxane) (PDMS) has been used as a negative friction layer in triboelectric nanogenerators (TENGs) owing to its high electronegativity and flexibility. With the advantage of PDMS, the ...design of various materials to further enhance the energy output of a PDMS-based TENG system have been suggested for practical applications. Herein, we report a high-efficiency PDMS-based TENG wherein surface-modified carbon nanotubes (SMCs), fabricated by one-step pulsed laser ablation, were used as a PDMS additive. SMCs possess oxygen-rich functional groups on the surface that enhance their permittivity and dispersibility in PDMS. Consequently, improvements in the triboelectric performance and capacitance of an SMC-PDMS-based TENG device (SMC-PDMS) were observed, owing to the synergistic effects of the enhanced permittivity and dispersibility of SMCs. Compared to a pristine PDMS-based TENG, SMC-PDMS containing 0.05 wt% SMCs showed an output voltage of 382.12 V and a current of 29.44 μA, which correspond to 170% and 243% enhancements, respectively. In addition, a facile radio frequency plasma treatment was performed to further improve the performance of SMC-PDMS, resulting in an output voltage of 414.63 V, a current of 40.03 μA, and a power density of 7.69 W m −2 .
The electrocatalytic performance of transition metal sulfide (TMS)–graphene composites has been simply regarded as the results of high conductivity and the large surface/volume ratio. However, ...unavoidable factors such as degree of oxidation of TMSs have been hardly considered for the origin of this catalytic activity of TMS–graphene composites. To accomplish the reliable application of TMS-based electrocatalytic materials, a clear understanding of the thermodynamic stability of TMS and effects of oxidation on catalytic activity is necessary. In addition, the mechanism of charge transfer at the TMS–graphene interface must be studied in depth to properly design composite materials. Herein, we report a comprehensive study of the physical chemistry at the junction of a Co1–x Ni x S2–graphene composite, which is a prototype designed to unravel the mechanisms of charge transfer between TMS and graphene. Specifically, the thermodynamic stability and the effects of oxidation of TMSs during the oxygen evolution reaction (OER) on the reaction mechanism are systematically investigated using density functional theory (DFT) calculations and experimental observations. Cobalt atoms anchored on pyridinic N sites in the graphene support form metal–semiconductor (SC) junctions, and the internal band bending at these junctions facilitates electron transfer from TMSs to graphene. The junction enables fast sinking of the excess electron from OH– adsorbate. Partially oxidized amorphous TMS layers formed during the OER can facilitate adsorption and desorption of OH and H atoms, boosting the OER performance of TMS–graphene nanocomposites. From the DFT calculations, the enhanced electrocatalytic activity of TMS–graphene nanocomposites originates from two important factors: (i) increased internal band bending and (ii) parallelized OER pathways at the interface of pristine and oxidized TMSs.
The introduction of a Cr and chromium nitride multi-coating barrier between the nuclear metallic fuel and the cladding is a potential candidate to mitigate fuel cladding chemical interaction (FCCI). ...Cr coatings were electroplated on HT9 disks using direct and pulse currents followed by plasma nitriding for synthesizing additional nitride coating. The pulse current induced Cr coatings revealed severe microstructural changes from crack-free to the abundance of cracks during the plasma nitriding due to phase transformation during the plasma nitriding. The phase transformation of hexagonal CrH to cubic Cr occurred at a temperature as low as 110 °C resulting in the liberation of hydrogen pores agglomerated at Cr grain boundaries and internal stress. Finally, the diffusion barrier property of the pulse current induced Cr coatings was significantly reduced, while the plasma-nitrided Cr coating produced by a direct current exhibited a crack-closure effect, and an additional nitride layer successfully hindered the elemental diffusion of Ce and Nd at 650 °C for 25 h. This current study points to the critical effect of current waveforms on the final barrier property of Cr-chromium nitride coatings for nuclear cladding applications.
The design of atomically dispersed single atom catalysts (SACs) must consider high metal-atom loading amount, effective confinement, and strong interactions with matrix, which can maximize their ...catalytic performance. Here reported is a promising method to synthesize SACs on highly conductive multiwall carbon nanotube (MWCNT) supports using pulsed laser confinement (PLC) process in liquid. Atomic cobalt (Co) and phosphorus (P) with a high loading density are homogeneously incorporated on the outer wall of the MWCNT (Co–P SAC MWCNT). Density functional theory (DFT) calculations in combination with systematic control experiments found that the incorporated Co and P adatoms act as an adsorption energy optimizer and a charge transfer promoter, respectively. Hence, favorable kinetics and thermodynamics in Co–P SAC MWCNT can be simultaneously achieved for water oxidation resulting in a superior catalytic performance than the benchmark RuO2 catalyst. Crucially, total processing time for assembling Co–P SAC MWCNT via PLC process is less than 60 min, shedding light on the promising practical applications of our SAC design strategy.
Transition metal doping and structural modification of MWCNT via PLA process show the significant enhancement of OER properties.
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•The pulsed laser ablation process can effectively ...incorporate transition metal.•The partially collapsed MWCNT enhanced active site for electrocatalysts.•Ni-doped MWCNTs presented excellent electrocatalysts properties.
Transition–metal-doped carbon-based electrocatalysts have attracted attention as alternatives to noble metal electrocatalysts (e.g. IrO2 and RuO2) for oxygen evolution reaction (OER) because they are inexpensive and highly efficient. However, their poor catalytic activity and time-consuming synthesis remain a challenge. Herein, we report a facile and green technique using pulsed laser ablation for preparing Ni-doped multi-walled carbon nanotubes (Ni-MWCNTs) as OER catalysts. Ni-MWCNTs exhibit high surface area, oxygen-rich functional groups (e.g., hydroxyl and carboxyl), and successful doping of Ni in the carbon framework. The as-prepared Ni-MWCNTs exhibited excellent OER catalytic performance, with an overpotential of 320 mV at the current density of 10 mA cm−2 in an alkaline medium, which is lower than that of the commercial RuO2 catalyst. Furthermore, Ni-MWCNTs displayed the initial electrocatalytic activity after 10-h stability tests, demonstrating good electrochemical durability. We believe that this work provides a simple protocol for fabricating heteroatom-doped carbon nanotubes as high-performance OER electrocatalysts.
Effect of Fe incorporation on electrical properties of (NixCoyMn3-x-y)O4 (NMC) spinel compound is investigated for the application to a negative temperature coefficient (NTC) thermistor. Cation ...distribution of the Fe doped NMC (FNMC) is calculated based on the size of ions located at tetragonal A sites and octahedral B sites in spinel structure, which can be closely related with temperature dependent electrical properties of the FNMC. With change of Fe contents, the ratio of Mn3+/Mn4+ in octahedral B site of FNMC is changed which can determine the temperature sensitivity factor (B-value). Hopping conduction mode relating with activation energy and hopping distance was also discussed depending on Fe contents, based on the small polaron hopping theory.
•Hopping mode in FNMC occurs through nearest neighboring hopping (NNH) motion when Fe content increases above 0.5.•Variable range hopping (VRH) motion was determined as hopping conduction mechanism for FNMC with Fe content lower than 0.5.•Cation distribution in FNMC with different Fe content is proposed based on the theoretical model.
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