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 (≈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.