To investigate the effect of carbon defects on the hydrophilicity of the whole surface of the coal pyrite, the adsorption of the single H₂O molecule at different sites of the coal pyrite surface was studied with the DFT calculation. It was found that, like the ideal pyrite, the single H₂O molecule can stably adsorb at the doping-position, the ortho-position and the meta-position of the coal pyrite. The covalent bond and anti-bond were formed between O (water molecule) and Fe (the coal pyrite) through the Fe 3d orbital and O 2p orbital. Meanwhile, the S–H bond was replaced by the C–H bond. But away from the carbon defect centre, the adsorption of the single H₂O molecule increased gradually and the Fe–O covalent bond strength between the single H₂O molecule and the pyrite strengthened, which eventually became close to that of the undoped coal pyrite surface.

Ni₃Si₂O₅(OH)₄ rods (NS) were synthesized via a hydrothermal method, employing natural wollastonite as a template. The hierarchical Ni₃Si₂O₅(OH)₄ rods exhibited vertically oriented nanosheets, resulting in a substantial increase in the specific surface area (from 2.24 m²/g to 178.4 m²/g). Subsequently, a CdS/Ni₃Si₂O₅(OH)₄ composite photocatalyst (CdS/NS) was prepared using a chemical deposition method. CdS was uniformly loaded onto the surface of the Ni₃Si₂O₅(OH)₄ nanosheets, successfully forming a heterojunction with Ni₃Si₂O₅(OH)₄. The CdS/NS photocatalyst in the presence of lactic acid as a sacrificial agent demonstrated an impressive H₂ production rate of 4.05 mmol h⁻¹ g⁻¹, around 40 times higher than pure CdS. The photocorrosion of CdS was effectively solved after loading. After four cycles, the performance of CdS/NS remained stable, showing the potential for sustainable applications. After photoexcitation, electrons moved from Ni₃Si₂O₅(OH)₄ to the valence band of CdS, where they interacted with the holes via an enhanced interface contact. Simultaneously, electrons in CdS transitioned to its conduction band, facilitating hydrogenation. The enhanced performance was attributed to the improved CdS dispersion by Ni₃Si₂O₅(OH)₄ loading and efficient photogenerated carrier separation through the heterojunction formation. This work provides new perspectives for broadening the applications of mineral materials and developing heterojunction photocatalysts with good dispersibility and recyclability.