Monodisperse Co9S8 nanoparticles in situ embedded within N, S-codoped honeycomb-structured porous carbon for bifunctional oxygen electrocatalyst in a rechargeable Zn–air battery

Abstract

The exploitation of cost-effective, highly active, and robust non-precious metal bifunctional oxygen electrocatalysts for both the oxygen reduction reaction (ORR) and oxygen revolution reaction (OER) is the key to promoting the application of regenerative fuel cells and metal-air batteries. Co 9 S 8 is considered a promising non-precious metal bifunctional oxygen electrocatalyst. However, the electrocatalytic performance of cobalt sulfide-based nanocatalysts is still far from satisfactory because of their poor conductivity, insufficient exposed active sites, and aggregation-prone during continuous work. Herein, based on the inspiration from honeycombs in nature, we synthesized Co 9 S 8 /N, Scodoped honeycomb-structured porous carbon (Co 9 S 8 /NSC) in situ composites via a simple method. Benefiting from the unique honeycomb composite structure composed of monodisperse Co 9 S 8 nanoparticles in situ embedded within the three-dimensional interconnected network carbon matrix with high conductivity, which facilitates not only the electron transport and charge transfer across the interface but also the exposure of active sites and rapid transport of ORR/OER-related species, the obtained Co 9 S 8 /NSC in situ composites exhibit high stability and activity in both the ORR in terms of more a positive half-wave potential (0.88 V vs. RHE) than that (0.86 V vs. RHE) of commercial 20% Pt/C and the OER in terms of a small overpotential (0.41 V vs. RHE) approaching that of commercial IrO 2 (0.39 V vs. RHE) in alkaline electrolytes at 10 mA cm −2 . Thus, as expected, the assembled rechargeable Zn-air batteries based on the bifunctional electrocatalysts exhibit a small discharge/charge overpotential (0.96 V) with a high voltaic efficiency of 55.1% at 10 mA cm −2 and a long-term cycling stability of over 4000 min.

Rational Design of Core@shell Structured CoSx@Cu2MoS4 Hybridized MoS2/N,S‐Codoped Graphene as Advanced Electrocatalyst for Water Splitting and Zn‐Air Battery

“…Figure 7 a displayed LSV curve in the range from 0.3 to 1.9 V with bifunctional catalytic behaviors of the CoS x @Cu 2 MoS 4 ‐MoS 2 /NSG toward ORR and OER. The potential difference (Δ E ) between ORR and OER (Δ E = E J = 10 − E half , where E J = 10 is the potential value to achieve a current response of 10 mA cm −2 for OER and E half is the half‐wave potential of ORR) was found to be 0.694 V. This result was much smaller than that of many reported metal‐based catalysts, demonstrating promising bifunctional ORR and OER activities of the CoS x @Cu 2 MoS 4 ‐MoS 2 /NSG for Zn‐air battery application. In order to realize its practicability, CoS x @Cu 2 MoS 4 ‐MoS 2 /NSG was used as a cathodic catalyst (1.6 mg cm −2 ) for constructing Zn‐air battery device (Figure b).…”

Facile Fabrication of Co9S8 Embedded in a Boron and Nitrogen Co‐Doped Carbon Matrix as Sodium‐Ion Battery Anode

“…It is worth noting that the carbon matrix can tight immobilize Co 9 S 8 nanoparticles and maintain the structural integrity. Selected area electron diffraction (SAED) performed on the region tested by TEM is shown in Figure c, which indicating the polycrystalline structure of Co 9 S 8 nanoparticles ,…”

Fe 7 S 8 nanoparticles encapsulated in porous N, S co‐doped carbon as an efficient bifunctional electrocatalyst for Zn‐air battery

“…The high‐resolution C 1s spectrum in Fig. 4 a can be split into four peaks located at 284.6, 285.3, 286.4, and 288.3 eV, corresponding to C–C=C, C–S–C, C–N–C, and C=O bond, respectively [5]. Fig.…”

“…4 c , S 2p spectra are mainly deconvoluted into four peaks at about 163.7, 164.8, 168.4, and 169.6 eV. The peaks at 163.7 and 164.8 eV can be assigned to S 2p1/2 and S 2p3/2, while the rest two peaks at 168.4 and 169.6 eV are relevant to the highly oxidised sulphur species [5]. As to the Fe 2p spectrum in Fig.…”

“…Despite the progress, transition metal chalcogenides suffer from low electrical conductivity, poor distribution, and nanoparticle agglomeration, leading to inferior electrocatalytic performance. Recently, introducing transition metal sulphides into heteroatom‐doped carbon materials to form a composite is considered as the most investigated technology, which can effectively improve the electrocatalytic activity and stability on account of the large specific surface area, great stability and high conductivity of carbon matrix [5]. Moreover, the presence of heteroatoms such as nitrogen and sulphur atoms will modify the electronic structures of carbon frameworks, form more defects, and offer more active sites, then remarkably boost the ORR and OER activity [6].…”