Transition-metal
sulfide is pursued for replacing scare platinum-group
metals for oxygen electrocatalysis and is of great importance in developing
low-cost, high-performance rechargeable metal–air batteries.
We report herein a facile cationic-doping strategy for preparing nickel-doped
cobalt sulfide embedded into a mesopore-rich hydrangea-like carbon
nanoflower. Nickel cations are introduced to induce the formation
of Co3+-active species and more oxygen vacancies due to
higher electronegativity and smaller ionic radius, thereby strengthening
the intrinsic activity for oxygen electrocatalysis. Moreover, hydrangea-like
superstructure composed of interconnected carbon cages provides abundant
accessible active sites and hierarchical porosity. As a result, it
shows excellent catalytic performance with a superior mass activity
for the oxygen reduction reaction to the state-of-the-art Pt/C catalyst
and a low overpotential of 314 mV at 10 mA cm–2 for
the oxygen evolution reaction. When used as an air cathode for the
rechargeable Zn–air battery, it delivers a peak power density
of 96.3 mW cm–2 and stably operates over 214 h.
This work highlights the importance of cationic doping in strengthening
the electrocatalytic performance of 3d-transition-metal chalcogenides.
Excellent proton‐conductive accelerators are indispensable for efficient proton‐exchange membranes (PEMs). Covalent porous materials (CPMs), with adjustable functionalities and well‐ordered porosities, show much promise as effective proton‐conductive accelerators. In this study, an interconnected and zwitterion‐functionalized CPM structure based on carbon nanotubes and a Schiff‐base network (CNT@ZSNW‐1) is constructed as a highly efficient proton‐conducting accelerator by in situ growth of SNW‐1 onto carbon nanotubes (CNTs) and subsequent zwitterion functionalization. A composite PEM with enhanced proton conduction is acquired by integrating CNT@ZSNW‐1 with Nafion. Zwitterion functionalization offers additional proton‐conducting sites and promotes the water retention capacity. Moreover, the interconnected structure of CNT@ZSNW‐1 induces a more consecutive arrangement of ionic clusters, which significantly relieves the proton transfer barrier of the composite PEM and increases its proton conductivity to 0.287 S cm−1 under 95 % RH at 90 °C (about 2.2 times that of the recast Nafion, 0.131 S cm−1). Furthermore, the composite PEM displays a peak power density of 39.6 mW cm−2 in a direct methanol fuel cell, which is significantly higher than that of the recast Nafion (19.9 mW cm−2). This study affords a potential reference for devising and preparing functionalized CPMs with optimized structures to expedite proton transfer in PEMs.
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