In-situ construction of 2D β-Co(OH)2 nanosheets hybridized with 1D N-doped carbon nanotubes as efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions

Abstract

• β-Co(OH) 2 nanosheets supported on doped carbon nanotubes is in-situ constructed. • The carbon plays predominant catalysis for ORR, and β-Co(OH) 2 for OER. • β-Co(OH) 2 /NCNTs shows excellent bifunctional activity with a Δ E = 0.69 V. • The battery displays a high specific capacity of 883 mAh/g at 30 mA cm −2. It is crucial to develop highly active and durable bifunctional electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for rechargeable Zn-air batteries. Herein, we report a facile approach to synthesize 2D β-Co(OH) 2 nanosheets supported on 1D nitrogen-doped carbon nanotubes through a hydrothermal in-situ growth strategy of Co nanoparticles encapsulated N-doped carbon nanotubes and urea. The as-obtained Co(OH) 2 /NCNTs displays excellent bifunctional activity with a high half-wave potential of 0.85 V vs. RHE for ORR, a low overpotential of 312 mV at 10 mA cm −2 for OER, and a low potential gap of 0.69 V. Density function theory calculations show that the synergistic effort between doped carbon and β-Co(OH) 2 reduces the energy barriers of the rate determining steps for the former toward ORR and for the latter toward OER, contributing to the superior bifunctional catalytic performance. The assembled Co(OH) 2 /NCNTs- based battery performs a high specific capacity of 883 mAh g Zn -1 and remarkable cycle stability. This presented in-situ construction strategy provides an attractive rational design method for preparing carbon-based bifunctional electrocatalysts.