The electroreduction of CO₂ to produce acetate is an extremely important and widely studied reaction. Herein, we report a heterogeneous electrocatalyst with Co₃O₄ nanoparticles immobilized on polyaniline (PANI) and cosupported by highly graphitized carbon (Co₃O₄/PANI/C) for the electroreduction of CO₂ to acetate with high activity and selectivity. Remarkably enhanced acetate Faraday efficiency (ca. 62%) and current density (ca. 35 mA∙cm⁻²) were obtained under conditions of static electroreduction at −0.95 V in 0.5 M KOH aqueous electrolyte while suppressing the competitive hydrogen evolution reaction. The excellent performance of Co₃O₄/PANI/C is attributed to the tandem effect of the Co₃O₄ nanoparticles with abundant oxygen vacancies and the PANI heterogeneous interface in a favorable configuration. Density functional theory calculations revealed that the tandem configuration of Co₃O₄/PANI/C facilitates the rapid delivery of the key *CO intermediate formed on Co₃O₄ to PANI, which increases the coverage of the intermediate *CO on the electrocatalyst surface, thus promoting acetate production during the CO₂ electroreduction reaction.

The growth of a Ni(OH)₂ coating on conductive carbon substrates is an efficient way to address issues related to their poor conductivity in electrochemical capacitor applications. However, the direct growth of nickel hydroxide coatings on a carbon substrate is challenging, because the surfaces of these systems are not compatible and a preoxidation treatment of the conductive carbon substrate is usually required. Herein, we present a facile preoxidation-free approach to fabricate a uniform Ni(OH)₂ coating on carbon nanosheets (CNs) by an ion-exchange reaction to achieve the in situ transformation of a MgO/C composite to a Ni(OH)₂/C one. The obtained Ni(OH)₂/CNs hybrids possess nanosheet morphology, a large surface area (278 m²/g), and homogeneous elemental distributions. When employed as supercapacitors in a three-electrode configuration, the Ni(OH)₂/CNs hybrid achieves a large capacitance of 2, 218 F/g at a current density of 1.0 A/g. Moreover, asymmetric supercapacitors fabricated with the Ni(OH)₂/CNs hybrid exhibit superior supercapacitive performances, with a large capacity of 198 F/g, and high energy density of 56.7 Wh/kg at a power density of 4.0 kW/kg. They show excellent cycling stability with 93% capacity retention after 10, 000 cycles, making the Ni(OH)₂/CNs hybrid a promising candidate for practical applications in supercapacitor devices.