CoS 2 Coatings for Improving Thermal Stability and Electrochemical Performance of FeS 2 Cathodes for Thermal Batteries

Photoelectrochemical water splitting is a promising approach to enhance the efficiency of water splitting. However, it is still challenging to develop an efficient oxygen evolution reaction (OER) electrocatalyst that can be coupled with light due to inefficient light utilization. Here, we demonstrate that N, Fe-co-doped CoS 2 (N, Fe−CoS 2 ) nanorod arrays can act as a highly efficient photo-coupled electrochemical OER catalyst. In dark conditions, the N, Fe-doped CoS 2 on selfsupported stainless steel (SS) mesh shows a small OER overpotential (215 mV) at a current density of 10 mA cm −2 , a reduced Tafel slope (43.2 mV dec −1 ), and negligible activity decay after 10 000 cycles. Upon visible−NIR light illumination, the N, Fe-doped anode exhibits superior photoelectrochemical performance because of the enhanced photoresponse, excellent light harvesting ability and promoted interfacial kinetics of charge separation. Our well-designed photoelectrochemical OER electrode can not only serve as a light absorption semiconductor but also the active catalytic sites for the OER reaction; the electrode composed of the single phase can efficiently avoid photocarrier recombination at the grain boundary. This study provides an insight into photoanode synthesis for photoelectrochemical OER and offers guidance on the future electrocatalyst design.

Section: Resultssupporting

confidence: 65%

“…3 The signal of S 2− can be ascribed to exposure to air, as reported in the previous literature. 2,12,26 The S−O signal results from surface oxidization of sulfides in air. 27 The N 1s peak (Figure 2h) located at 399.8 eV corresponds to the Co−N bond, indicating that N atoms are successfully doped into the CoS 2 matrix.…”

Section: ■ Introductionmentioning

confidence: 99%

Robust Photoelectrochemical Oxygen Evolution with N, Fe–CoS₂ Nanorod Arrays

Cai

Zhang

et al. 2019

“…Further analysis of the high-resolution S 2p spectra is shown in Figure S5, which can give more insightful information about the chemical states and bonding of sulfur. The peak locates at 161.8 and 163.0 eV can be assigned as the 2p 3/2 and 2p 1/2 spin–orbit levels of the Co–S bond, with an energy separation of 1.13 eV and intensity ratio of 2:1, whereas the high-intensity peak at 168.25 eV is attributed to the existence of the S–O group, which might come from the minor oxygen-containing functional group on the surface during manipulation of the sample. − A predominate S 2 2– peak at 163.0 eV indicates the presence of unsaturated sulfur atoms on the surface, which is also observed in the pure CoS 2 sample. As C–S bonding exists at ∼163.0 eV, which might not exist on the surface, the binding between HPGC and CoS 2 cannot be identified by XPS separately.…”

Section: Results and Discussionmentioning

confidence: 99%

Investigation of the Nanocrystal CoS₂ Embedded in 3D Honeycomb-like Graphitic Carbon with a Synergistic Effect for High-Performance Lithium Sulfur Batteries

Zhang

et al. 2019

Lithium sulfur (Li–S) batteries can offer great opportunities for the next-generation energy storage systems with tremendous energy density. However, challenges still exist in practical Li–S batteries including low sulfur utilization, and poor cycling stability and rate capability. Herein, we propose a novel hybrid catalyst structure by in situ implanting nanocrystal CoS2 in three-dimensional honeycomb-like hierarchical porous graphitic carbon (HPGC) for high-performance Li–S batteries. A unique synergistic absorption-catalysis-functional effect is demonstrated by comprehensive experimental and theoretical analysis: strong physical and chemical co-absorption effects are originated from the large quantity of microporous HPGC and the polar surface of metallic CoS2; the introduced nanocrystal CoS2 with a large specific area can impose an exceptional catalytic effect on the liquid–liquid, solid–liquid, and solid–solid phase redox reactions in Li–S batteries; the reaction dynamics are further guaranteed by the multifunctional properties of the HPGC backbone, including the capabilities in polysulfide sustention, reaction product transportation, electrolyte compensation, and efficiency in assisting diverse electrochemical reaction dynamics. In this way, our results not only develop a novel CoS2@HPGC structure, but also provide fundamental understanding on the catalytic dynamics during each reaction process. Moreover, we further propose the necessity and philosophy of the rational design of catalysts’ special structure, which can fulfill the functional dynamics requirements of Li–S batteries, and can be promoted to other Li–S-related cathode design and composite catalytic structure design.

“…Apart from the preparation mode, developing new materials via coating, doping, or alloying strategies is an effective means for improving the performance of a thermal battery cathode. 10,11,15,29,30,34 However, the carbon coating significantly prolongs the activation time of the thermal battery (the nongraphite amorphous carbon layer hinders the intercalation of Li + ). 17 Therefore, the specific energy of the thermal battery is highly increased using the alloyed cathode.…”

Section: ■ Introductionmentioning

confidence: 99%

“…This enables the specific capacity of the cathode to be closer to the theoretical value and hence provides higher pulse performance. ,,,, Interestingly, in terms of the high-specific-energy battery design, the advantages of films are significantly reduced, which considerably increases the sheet thickness because such batteries require more active materials. Apart from the preparation mode, developing new materials via coating, doping, or alloying strategies is an effective means for improving the performance of a thermal battery cathode. ,,,,, However, the carbon coating significantly prolongs the activation time of the thermal battery (the nongraphite amorphous carbon layer hinders the intercalation of Li + ) . Therefore, the specific energy of the thermal battery is highly increased using the alloyed cathode.…”

Section: Introductionmentioning

confidence: 99%

Cobalt-Doped NiS₂ Micro/Nanostructures with Complete Solid Solubility as High-Performance Cathode Materials for Actual High-Specific-Energy Thermal Batteries

Guo

Tang

Tian

et al. 2020

Transition-metal sulfides are key cathode materials for thermal batteries used in military applications. However, it is still a big challenge to prepare sulfides with good electronic conductivity and thermal stability. Herein, we rapidly synthesized a Co-doped NiS2 micro/nanostructure using a hydrothermal method. We found that the specific capacity of the Ni1–x Co x S2 micro/nanostructure increases with the amount of Co doping. Under a current density of 100 mA cm–2, the specific capacity of Ni0.5Co0.5S2 was about 1565.2 As g–1 (434.8 mAh g–1) with a cutoff voltage of 1.5 V. Owing to the small polarization impedance (5 mΩ), the pulse voltage reaches about 1.74 V under a pulse current of 2.5 A cm–2, 30 ms. Additionally, the discharge mechanism was proposed by analyzing the discharge product according to the anionic redox chemistry. Furthermore, a 3.9 kg full thermal battery is assembled based on the synthesized Ni0.5Co0.5S2 cathode materials. Notably, the full thermal battery discharges at a current density of 100 mA cm–2, with an operating time of about 4000 s, enabling a high specific energy density of around 142.5 Wh kg–1. In summary, this work presents an effective cathode material for thermal battery with high specific energy and long operating life.