Nb2O5/g-C3N4 Composite Photocatalysts Supported on Etna-Derived Aluminosilicate for Solar H2 Production

In this work, Etna ash-derived photocatalysts were investigated for the first time for solar H2 production. Volcanic ash, commonly treated as a special waste in eastern Sicily (Italy), was modified through chemical treatment followed by microwave-assisted crystallization, avoiding the conventional high-temperature thermal route. The obtained material was tested both as a bare photocatalyst and as a support for a Nb2O5/graphitic carbon nitride composite prepared by a hydrothermal method. The Etna-derived photocatalyst exhibited a solar H2 production rate (by TEOA photoreforming) of 920 μmol/gcat·h. Upon incorporation of the Nb-based composite, the H2 evolution rate increased by about 2.5 times, reaching 2370.5 μmol/gcat·h, demonstrating a strong synergistic effect. Notably, the developed materials largely outperformed commercial TiO2 P25 (25 μmol/gcat·h). The enhanced photocatalytic activity was attributed to the tailored modifications of Etna ash, which increased porosity and promoted aluminosilicate framework reorganization, favoring an optimal distribution of the photocatalytically active TiO2 and iron oxide phases. The obtained Nb oxide/carbon nitride supported on modified Etna ash also showed a remarkable stability after six consecutive runs of solar photocatalytic H2 production. This work demonstrates a sustainable strategy for converting volcanic waste into efficient multifunctional photocatalysts while minimizing the use of critical raw materials.