ZnO@C Microballs Wrapped with Ni(OH)2 Nanofilms for Electrochemical Sensing of Glucose and Hydrogen Peroxide.

Tailor-made metal oxide/hydroxide core-shell structures are promising for the fabrication of effective electrocatalysts. Here, we report the development of a core-shell structure based on carbon-doped and Ni(OH)2 nanofilms wrapped ZnO microballs (NFs-Ni(OH)2 /ZnO@C MBs) for glucose and hydrogen peroxide (H2 O2 ) monitoring. The unique ball-like morphology of the designed structure is achieved through a facile solvothermal strategy by the control of reaction conditions. Typically, ZnO@C MBs offer highly conductive core, and the shell of Ni(OH)2 nanofilms increases the density of catalytic active sites. The interesting morphology and the brilliant electrocatalytic efficacy of designed hybrid, encourage us to design a multi-mode sensor for glucose and H2 O2 screening. The NFs-Ni(OH)2 /ZnO@C MBs/GCE glucose sensor presented good sensitivities (647.899 & 161.550 µA (mmol L-1 )-1 cm-2 ), a quick response (<4 s), lower limit of detection (0.04 µmol L-1 ), and wide detection range (0.004-1.13 & 1.13-5.02 mmol L-1 ). Similarly, the same electrode revealed excellent H2 O2 sensing features including good sensitivities, two linear parts of 3.5-452 and 452-1374 µmol L-1 , and detection limit of 0.03 µmol L-1 as well as high selectivity. Thus, the development of novel hybrid core-shell structure is useful for potential applications in glucose and H2 O2 screening from environmental and physiological samples.

Composition-adjustable Mo6Co6C2/Co@carbon nanocage for enhanced oxygen reduction and evolution reactions.

Bifunctional oxygen electrocatalysts that hold outstanding activity and stability are highly crucial for the development of efficient rechargeable Zn-air batteries. Herein, cobalt-molybdenum-based bimetallic carbide and cobalt nanoparticles embedded N-doped carbon nanocages are synthesized via the pyrolysis of functionalized zeolitic imidazolate framework precursor originated from zeolitic imidazolate framework sequentially coated with polydopamine and phosphomolybdic acid. Furthermore, we revealed the composition-performance relationship based on the exploration of bifunctional performance on the pyrolysis products. More importantly, the synergy of multiple active sites with hollow structure gives the prepared catalyst a low overpotential (284 mV) for oxygen evolution reaction and high half-wave potential (0.865 V) for oxygen reduction reaction, besides an excellent bifunctional durability. Furthermore, the prepared catalyst as a cathode electrocatalyst grants the assembled rechargeable Zn-air batteries a high open-circuit voltage, power density, specific capacity, and remarkable charge-discharge cycle stability. This work provides a strategy for the integration and active-adjustment of bifunctional catalyst and its potential applications in water splitting and other catalytic reactions.