Atomic‐Level Coupled Interfaces and Lattice Distortion on CuS/NiS₂ Nanocrystals Boost Oxygen Catalysis for Flexible Zn‐Air Batteries

Abstract

The exploration of highly efficient nonprecious metal bifunctional electrocatalysts to boost oxygen evolution reaction and oxygen reduction reaction is critical for development of high energy density metal-air batteries. Herein, a class of CuS/NiS 2 interface nanocrystals (INs) catalysts with atomic-level coupled nanointerface, subtle lattice distortion, and plentiful vacancy defects is reported. The results from temperature-dependent in situ synchrotron-based X-ray absorption fine spectroscopy and electron spin resonance spectroscopy demonstrate that the lattice distortion of 14.7% in CuS/NiS 2 caused by the strong Jahn-Teller effect of Cu, the strong atomic-level coupled interface of CuS and NiS 2 domains, and distinct vacancy defects can provide numerous effective active sites for their excellent bifunctional performance. A liquid Zn-air battery with the CuS/NiS 2 INs as air electrode displays a large peak power density (172.4 mW cm −2 ), a high specific capacity (775 mAh g Zn −1 ), and long cycle life (up to 83 h), making the CuS/NiS 2 INs among the best bifunctional catalysts for Zn-air battery. More remarkably, the flexible CuS/NiS 2 INsbased solid-state Zn-air batteries can power the LED after twisting, making them be promising in portable and wearable electronic devices.

CuCo2S4 Nanosheets@N‐Doped Carbon Nanofibers by Sulfurization at Room Temperature as Bifunctional Electrocatalysts in Flexible Quasi‐Solid‐State Zn–Air Batteries

“…[19,[38][39][40][41][42] With the incorporation of Cu, the CuCo-based electrocatalysts display a higher catalytic activity due to their tailored electron transfer between Cu and Co ions. [19,[38][39][40][41][42] With the incorporation of Cu, the CuCo-based electrocatalysts display a higher catalytic activity due to their tailored electron transfer between Cu and Co ions.…”

“…[47,48] As a result, the highly conductive N-CNFs film in our designed electrode not only guarantees the extraordinary flexibility for quasi-solid-state ZAB devices, but also provides the fast electron transfer kinetics for the CuCo 2 S 4 NSs. [19,47] As illustrated in Figure 4e, together with the XANES analyses and electrocatalytic results, the factors affecting the ORR/ OER performances of CuCo 2 S 4 NSs@N-CNFs could be summarized as follows: 1) the highly nitridated N-CNFs film with highly conductive and strong electrostatic force offers more ORR active sites ( Figure S16, Supporting Information); 2) the intrinsic activity and electrical conductivity are both improved after in situ sulfurization from CuCo 2 O 4 NPs to CuCo 2 S 4 NSs, which leads to a superior electrocatalytic OER/ORR activity; 3) the nanosheets' feature of multiple valances CuCo 2 S 4 can be acted as a "nanometers highway" for electron transport; and 4) the large specific surface area originating from the CuCo 2 S 4 NSs@N-CNFs core/shell nanostructure. Furthermore, Figure 4c shows the corresponding Fourier transform (FT) k 3 χ(k) function of the extended X-ray absorption fine structure (EXAFS) spectroscopy for CuCo 2 S 4 NSs@N-CNFs at Co K-edge in R-space.…”

“…[1][2][3][4][5][6][7][8] In principle, the advancement of flexible ZABs is critically dependent on the availability of desired air electrodes with excellent bifunctional electrocatalysis for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), together with robust flexibility and mechanical strength. [19][20][21][22][23][24][25][26][27] For example, CuCo 2 O 4 quantum dots attached on N-doped carbon nanotubes (CuCo 2 O 4 @NCNTs) were shown to be an impressively bifunctional electrocatalyst including a good positive half-wave potential (0.80 V) for ORR and a low overpotential (467 mV@10 mA cm −2 ) for OER, which can contribute to an energy density of 659 W h kg −1 (in liquid state) for ZAB. Bimetallic oxides (BOs)@heteroatom-doped carbon hybrids have drawn considerable attentions, because of their high catalytic efficiency, derived from the synergetic effects between the nanostructured BOs (for OER) and N-doping in carbon materials (for ORR).…”

“…[9][10][11][12][13][14][15][16][17][18] For this purpose, several types of cathode materials have been explored. [23] Although great progress has been made recently with BOs@NC-based ZABs in liquid state, [19][20][21][22][23][24][25][26][27] the overall performances in quasi-solid-state are still far away from those key The performance of quasi-solid-state flexible zinc-air batteries (ZABs) is critically dependent on the advancement of air electrodes with outstanding bifunctional electrocatalysis for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), together with the desired mechanical flexibility and robustness. [19][20][21][22][23][24][25][26][27] For example, CuCo 2 O 4 quantum dots attached on N-doped carbon nanotubes (CuCo 2 O 4 @NCNTs) were shown to be an impressively bifunctional electrocatalyst including a good positive half-wave potential (0.80 V) for ORR and a low overpotential (467 mV@10 mA cm −2 ) for OER, which can contribute to an energy density of 659 W h kg −1 (in liquid state) for ZAB.…”

Electric‐Field‐Assisted Enhanced Electron Transfer to Boost Supercapacitor Negative Electrode Performance for a Fabricated Fe7S8/α‐FeOOH Nano‐Heterostructure

“…To further obtain the detailed crystal parameters, high-magnification STEM tests were carried out (Figure 2d www.advelectronicmat.de heterojunction structures that were found. [30,31] The heterostructure of Fe 7 S 8 /α-FeOOH is shown clearly in Figure S8, Supporting Information, and the inset in Figure 2e, which reveals that the α-FeOOH and Fe 7 S 8 are interweaved with each other to provide more interfacial area. The lattice distance of 0.250 nm is attributed to the (040) plane of α-FeOOH while that of 0.298 nm to the (200) plane of Fe 7 S 8 .…”