Recycling Rusty Iron with Natural Zeolite Heulandite to Create a Unique Nanocatalyst for Green Hydrogen Production

Corrosion-induced iron rust causes severe danger, pollution, and economic problems. In this work, nanopowders of Fe₂O₃ and Fe₂O₃/zeolite are synthesized for the first time using rusted iron waste and natural zeolite heulandite by chemical precipitation. The chemical composition, nanomorphologies, structural parameters, and optical behaviors are investigated using different techniques. The Fe₂O₃/zeolite nanocomposite showed smaller sizes and greater light absorption capability in visible light than Fe₂O₃ nanopowder. The XRD pattern shows crystalline hematite (α-Fe₂O₃) with a rhombohedral structure. The crystallite sizes for the plane (104) of the Fe₂O₃ and Fe₂O₃/zeolite are 64.84 and 56.53 nm, respectively. The Fe₂O₃ and Fe₂O₃/zeolite have indirect bandgap values of 1.87 and 1.91 eV and direct bandgap values of 2.04 and 2.07 eV, respectively. Fe₂O₃ and Fe₂O₃/zeolite nanophotocatalysts are used for solar photoelectrochemical (PEC) hydrogen production. The Fe₂O₃/zeolite exhibits a PEC catalytic hydrogen production rate of 154.45 mmol/g.h @ 1 V in 0.9 M KOH solution, which is the highest value yet for Fe₂O₃-based photocatalysts. The photocurrent density of Fe₂O₃/zeolite is almost two times that of Fe₂O₃ catalyst, and the IPCE (incident photon-to-current conversion efficiency) reached ~27.34%@307 nm and 1 V. The electrochemical surface area (ECSA) values for Fe₂O₃ and Fe₂O₃/zeolite photocatalysts were 7.414 and 21.236 m²/g, respectively. The rate of hydrogen production for Fe₂O₃/zeolite was 154.44 mmol h^-1/g. This nanophotocatalyst has a very low PEC corrosion rate of 7.6 pm/year; it can retain ~97% of its initial performance. Therefore, the present research can be applied industrially as a cost-effective technique to address two issues at once by producing solar hydrogen fuel and recycling the rusted iron wires.