Co/MoC Nanoparticles Embedded in Carbon Nanoboxes as Robust Trifunctional Electrocatalysts for a Zn-Air Battery and Water Electrocatalysis

To meet the application needs of rechargeable Zn-air battery and electrocatalytic overall water splitting (EOWS), developing high-efficiency, cost-effective, and durable trifunctional catalysts for the hydrogen evolution reaction (HER), oxygen evolution, and reduction reaction (OER and ORR) is extremely paramount yet challenging. Herein, the interface engineering concept and nanoscale hollowing design were proposed to fabricate N-doping carbon nanoboxes confined with Co/MoC nanoparticles. Uniform zeolitic imidazolate framework nanocube was employed as the starting material to construct the trifunctional electrocatalyst through the conformal polydopamine-Mo layer coating and the subsequent pyrolysis treatment. The Co@IC/MoC@PC catalyst displayed superior electrochemical ORR performances with a positive half-wave potential of 0.875 V and a high limiting current density of 5.89 mA/cm². When practically employed as an electrocatalyst in regenerative Zn-air battery, a high specific capacity of 728 mAh/g, a large peak power density of 221 mW/cm², a high open-circuit voltage of 1.482 V, and a low charge/discharge voltage gap of 0.41 V were obtained. Moreover, its practicability was further exploited by overall water splitting, affording low overpotentials of 277 and 68 mV at 10 mA/cm² for the OER and HER in 1 M KOH solution, respectively, and a decent operating potential of 1.57 V for EOWS. Ultraviolet photoelectron spectroscopy and density functional theory calculation revealed that the Co/MoC interface synergistically facilitated the charge-transfer, thereby contributing to the enhancements of electrocatalytic ORR/OER/HER processes. More importantly, this catalyst design concept can offer some interesting prospects for the construction of outstanding trifunctional catalysts toward various energy conversion and storage devices.