Boosting the primary Zn-air battery oxygen reduction performance with mesopore-dominated semi-tubular doped-carbon nanostructures

The low surface density of catalytic sites and undeveloped porosity have become a bottleneck for boosting the oxygen reduction reaction (ORR) activity of carbon catalysts. Herein, we propose a novel strategy for the synthesis of porous semi-tubular iron-nitrogen-doped-carbon nanostructures via a two-step calcination of a ferriporphyrin-based biomaterial by means of a natural tubulose nanoclay as a morphology-controlled template, followed by post Zn-activation and acid-leaching processes. The formation of mesopore-dominated semi-tubular carbons is beneficial for accelerating the ORR catalysis rate and improving the catalytic activity owing to the increased mass transport capacity of reactants to nitrogen-rich catalytic sites existing in the pores. The resultant doped-carbon catalyst not only displays excellent electrocatalytic behavior with an ORR onset potential of similar to 1.01 V and a half-wave potential of similar to 0.85 V, but also exhibits a maximum power density of similar to 191 mW cm(-2), comparable to that of a Pt catalyst in a primary Zn-air battery, suggesting a very promising candidate for prevalent energy-conversion devices. It is probably due to the production of mesopore-dominated semi-tubular structures, more active-nitrogen species and dense surface active sites. This work can pave a new way for the original design of low-cost and high-performance doped-carbon catalysts by using natural biomaterials for widespread application in electrochemical energy devices.