Integrated Hierarchical Carbon Flake Arrays with Hollow P-Doped CoSe2 Nanoclusters as an Advanced Bifunctional Catalyst for Zn-Air Batteries

Hierarchical nanostructured architectures are demonstrated as an effective approach to develop highly active and bifunctional electrocatalysts, which are urgently required for efficient rechargeable metal-air batteries. Herein, a mesoporous hierarchical flake arrays (FAs) structure grown on flexible carbon cloth, integrated with the microsized nitrogen-doped carbon (N-doped C) FAs, nanoscaled P-doped CoSe2 hollow clusters and atomic-level P-doping (P-CoSe2/N-C FAs) is described. The P-CoSe2/N-C FAs thus developed exhibit a reduced overpotential (approximate to 230 mV at 10 mA cm(-2)) toward oxygen evolution reaction (OER) and large half-wave potential (0.87 V) for oxygen reduction reactions. The excellent bifunctional electrocatalytic performance is ascribed to the synergy among the hierarchical flake arrays controlled at both micro- and nanoscales, and atomic-level P-doping. Density functional theory calculations confirm that the free energy for the potential-limiting step is reduced by P-doping for OER. An all-solid-state zinc-air battery made of the P-CoSe2/N-C FAs as the air-cathode presents excellent cycling stability and mechanical flexibility, demonstrating the great potential of the hierarchical P-CoSe2/N-C FAs for advanced bifunctional electrocatalysis.