The sluggish reaction kinetics in oxygen reduction reaction (ORR) is one of the bottlenecks in next generation energy conversion systems. The integrated design strategy based on simultaneously constructing active sites and forming porous carbon network will address this concern by facilitating charge exchange, mass transfer and electron transportation. In this article, a three-dimensional integrated air electrode (Co–N@ACS) containing Co–N sites and hierarchically porous carbon is fabricated via growth of Co-doped ZIF-8 in activated wood substrate and synchronous pyrolysis. The optimized integrated air electrodes exhibit ultrahigh ORR activity (E_1/2 = 0.86 V). Co–N sites provide outstanding ORR activity, and hierarchically porous structures facilitate oxygen diffusion and electrolyte penetration. Aqueous zinc-air battery assembled with Co–N@ACS possesses open-circuit voltage of 1.46 V, peak power density of 155 mW·cm^-2 and long-term stability of 540 cycles (180 h). Solid-state zinc-air battery assembled with Co–N@ACS shows open-circuit voltage up to 1.36 V and low charge-discharge voltage gap (0.8 V). This design strategy paves the way for the conversion of wood biomass to integrated air electrodes and catalytically active carbon for next generation energy storage and conversion devices.

The development of efficient catalytic electrode toward oxygen reduction reaction (ORR) is still a great challenge for the wide use of zinc–air batteries. Herein, Co₂N nanoparticles (NPs) anchored on N-doped carbon from cattail were verified with excellent catalytic performances for ORR. The onset and half-wave potentials over the optimal catalyst reach to 0.96 V and 0.84 V, respectively. Current retention rates of 96.8% after 22-h test and 98.8% after running 1600 s were obtained in 1 M methanol solution. Density functional theory simulation proposes an apparently increased electronic states of Co₂N in N-doped carbon layer close to the Fermi level. Higher charge density, favorable adsorption, and charge transfer of intermediates originate from the coexistence of Co₂N NPs and N atoms in carbon skeleton. The superior catalytic activity of composites also was confirmed in zinc–air batteries. This novel catalytic property and controllable preparation approach of Co₂N-carbon composites provide a promising avenue to fabricate metal-containing catalytically active carbon from biomass.