Recovering red mud to construct iron-aluminum oxides hybridized system for superior green hydrogen energy from water splitting

Herein, a novel iron-aluminum oxides/graphitic carbon nitride (FeAlOx/GCN) heterojunction has been successfully synthesized by facile calcination of melamine and FeAlOx from bauxite residues for superior solar-to-hydrogen-conversion efficiency to produce green H2 energy. The red mud is firstly treated by concentrated acid to separate iron and aluminum, which is further used to prepare amorphous FeAlOx. Subsequently, the FeAlOx/GCN composite is fabricated by tightly coupling FeAlOx with GCN via an in situ calcination route. The established heterojunction can effectively improve the light absorption capacity and speed up separation and transfer of the photogenerated electrons and holes. The findings indicate that surface defects are generated on the surface of FeAlOx/GCN composite, which can provide more available active sites for H2 production. As a result, the FeAlOx/GCN hybrids exhibit a superior photocatalytic H2 production in comparison with pure GCN or FeAlOx under the simulated sunlight irradiation. Among these samples, the optimized FeAlOx/GCN-1 exhibits the best photocatalytic activity, achieving to 5291 μmol g−1, which is 8.33 times higher than that of pure GCN (635 μmol g−1). This work provides a chance to efficiently recover valuable components from industrial solid waste to produce green H2 by using sustainable solar energy.