Recovered Carbon from Coal Gasification Fine Slag as Electrocatalyst for Oxygen Reduction Reaction and Zinc–Air Battery

The coal gasification industry produces a large amount of coarse and fine slag. Such slag, which is composed mainly of carbon residues and inorganic species, e.g., silicon, calcium, magnesium, and aluminum, becomes a tough problem because of the environmental concerns and high reusage cost. Benefiting from the carbon‐rich feature, such cheap byproducts of the coal gasification industry can be used as precursors to prepare porous carbons for energy conversion and storage. Herein, new porous carbons are prepared by treating carbon‐rich fine slag by direct acid etching and ammonia activation. The oxygen reduction reaction performance of as‐developed porous carbons as electrocatalysts is evaluated in alkaline media. Then, such porous carbons are further utilized as air cathodes for a zinc–air battery and reach a power density of 88 mW cm −2 at the current density of 154.9 mA cm −2 . All these results indicate that fine slag, a byproduct of the coal gasification industry, has a great potential to be reused as a high‐value electrocatalyst and electrode for energy conversion and storage.