Ni x Co1-x @Ni x Co1-x O/NCNT as Trifunctional ORR, OER, and HER Electrocatalysts and its Application in a Zn-Air Battery

The efficient electrochemical conversionand storage devices canbe boosted by the development of cost-effective and durable electrocatalysts.However, simultaneous in-depth understanding of the reaction mechanismis also required. Herein, we report the preparation, characterization,and electrochemical activities of bimetallic Ni x Co1-x NPs and core-shellNi( x )Co(1-x )@Ni x Co1-x O NPs stabilized on N-doped carbon nanotubes (NCNTs). The electrocatalystis derived from a bimetallic MOF {[Ni0.5Co0.5(bpe)(2)(N-(CN)(2))]-(N-(CN)(2))center dot(5H(2)O)}( n ) (1) via pyrolysis followedby calcination. Pyrolysis of the bimetallic MOF gives rise to bimetallicnanoparticles stabilized on NCNTs, which, when subsequently calcined,leads to the formation of a core-shell structure with a semiconductingoxide shell (Ni x Co1-x O) encapsulating the Ni x Co1-x bimetallic NP core. Detailedevaluation of the electrocatalytic performance of Ni x Co1-x @Ni x Co1-x O/NCNT proves its worthas a bifunctional catalyst with 380 mV overpotential for oxygen evolutionreaction at 10 mA cm(-2) current density and 0.87V (vs RHE) onset for oxygen reduction reaction in the alkaline medium.Additionally, the prepared electrocatalyst efficiently catalyzes thehydrogen evolution reaction with a nominal overpotential of 74 mV(vs RHE) for reaching 10 mA cm(-2) current densityin acidic medium. The practical applicability of this catalyst isfurther upheld in the fabrication of a zinc-air battery havinghigh specific capacity with high round-trip efficiency and adequatecycle life. DFT calculations establish that the structure of Ni x Co1-x @Ni x Co1-x O/NCNTis crucial for its electrochemical activity since it has the threefoldadvantages of cooperative charge transfer from Co to Ni, synergisticrelationship between the conductive alloy core and semiconductingoxide shell, and a highly conductive N-doped CNT matrix.

Automated summary

In this study, bimetallic Ni x Co1-x nanoparticles and core-shell Ni(x)Co(1-x)@Ni x Co1-x O nanoparticles stabilized on N-doped carbon nanotubes were prepared and characterized. The electrocatalyst exhibited excellent performance in oxygen evolution reaction, oxygen reduction reaction, and hydrogen evolution reaction. The structure of Ni x Co1-x @Ni x Co1-x O/NCNT was found to be crucial for its electrochemical activity.