Nanopore Confinement of Electrocatalysts Optimizing Triple Transport for an Ultrahigh‐Power‐Density Zinc–Air Fuel Cell with Robust Stability

Abstract

electrocatalysts to improve their catalytic activity and stability, the realization of a stable and efficient ORR on air electrodes remains a challenge. [4] Generally, advanced metal-air fuel cells require high power output and robust stability. It is vital to build a stable triplephase reaction interface on the electrocatalyst to achieve a perfect balance among electron conduction, oxygen gas diffusion, and ion transportation. [5] However, the masking of active sites in the disorderly stacked electrocatalyst layer in a metalair fuel cell results in sluggish electron transfer. This phenomenon will greatly reduce the efficiency of electron and ion transport, leading to a distinct reduction in the power density. [6] Moreover, the fragile triple-phase interface is easily eroded by water under long-term high current discharging, thereby blocking the oxygen gas transport channel, and causing a significant decline in the stability of the Zn-air fuel cell. [7] To address these issues, the most common strategy is to mix the electrocatalyst and hydrophobic polymer to form a stable three-phase interface and gas transmission channel. In this case, excessive polymer addition greatly increases the reaction resistance and reduces the power density of the Zn-air fuel cell. [8-10] However, fabricating binder-free air electrodes by directly growing electrocatalysts on a conductive substrate can significantly enhance the electrical conductivity. Unfortunately, numerous catalytic sites will be eroded by water flooding in the long-term reaction Metal-air fuel cells with high energy density, eco-friendliness, and low cost bring significantly high security to future power systems. However, the impending challenges of low power density and high-current-density stability limit their widespread applications. In this study, an ultrahigh-power-density Zn-air fuel cell with robust stability is highlighted. Benefiting from the water-resistance effect of the confined nanopores, the highly active cobalt cluster electrocatalysts reside in specific nanopores and possess stable triple-phase reaction areas, leading to the synergistic optimization of electron conduction, oxygen gas diffusion, and ion transport for electrocatalysis. As a result, the as-established Zn-air fuel cell shows the best stability under high-current-density discharging (>90 h at 100 mA cm −2) and superior power density (peak power density: >300 mW cm −2 , specific power: 500 Wg cat −1) compared to most reported non-noble-metal electrocatalysts. The findings will provide new insights in the rational design of electrocatalysts for advanced metal-air fuel cell systems. Metal-air fuel cells are indispensable as next-generation energy storage systems because of their high energy density, eco-friendliness, and low cost. [1] However, the low power density and vulnerable stability of metal-air fuel cells seriously impede their large-scale applications. In particular, a highly efficient and stable power output will be indispensable for emergency backup power supply in future smart po...

Boosting the Rate Performance of Li–S Batteries via Highly Dispersed Cobalt Nanoparticles Embedded into Nitrogen-Doped Hierarchical Porous Carbon

“…Note that the diffraction peak of metallic Co is absent as a consequence of the low Co content in Co@N-HPC. 43 Moreover, the Raman results (Figure 2b) suggest that the intensity ratio of G band (1590 cm -1 ) to D band (1330 cm -1 ) (I G /I D ) is higher for Co@N-HPC (1.02) compared with that of N-HPC (0.92) and N-C (0.87), 44 implying the higher graphitization degree and therefore promoted electrical conductivity for Co@N-HPC. The N 2 adsorption and desorption isotherms show the characteristics of typical IV isotherms with the pore size of 5-20 nm, indicating that Co@N-HPC is mainly dominated by mesoporous structure (Figure 2c, d).…”

“…The overall spectral shape of Co@N-HPC is similar to that of Co foil (Figure 2f), reflecting the dominated metallic property of Co in Co@N-HPC. 43 Moreover, in contrast to CoO, only one dominant peak at 2.12 Å is observed for the Fourier-transformed EXAFS (FT-EXAFS) spectrum of Co@N-HPC (Figure 2g), corresponding to the first shell scattering of the Co-Co bond. Note that the Co-Co bond length of Co@N-HPC is slightly shorter that of Co foil, which could be related to the size effect of Page 12 of 33 CCS Chemistry This article presented here has been accepted for publication in CCS Chemistry and is posted at the © 2021 Chinese Chemical Society.…”

Highly-dispersed and high-metal-density electrocatalysts on carbon supports for the oxygen reduction reaction: from nanoparticles to atomic-level architectures

“…Recently, Zhou et al have devised porous carbon limited Co SCCs (Co/PC SCCs) as an efficient electrocatalyst for the ORR in alkaline electrolyte via a "top-down approach" from carbon black [136].…”

Identification of the Intrinsic Dielectric Properties of Metal Single Atoms for Electromagnetic Wave Absorption

“…Atomic metal-N x (M-N x ) moieties anchored onto carbon support (M-N x C) can effectively modulate the electronic structures of adjacent carbon atoms, resulting in extraordinary physicochemical properties of M-N x Cs [1][2][3][4]. Moreover, well-defined single atomic sites provide an ideal platform for understanding the physicochemical mechanism at the atomic level [5][6][7][8][9]. In addition, carbon supports with high electrical conductivity are readily available for commercial use, which guarantees their applicability to various fields.…”