Investigation on Fe₂O₃/por-Si photocatalyst for low-bias water-splitting

A heterostructure of Fe₂O₃ and porous silicon (por-Si) as a photocatalyst in water splitting has been reported in this article. The heterostructure was formed by depositing around 200 nm thin layer of n-type α-Fe₂O₃ on a macro-porous silicon substrate with aluminium as a back contact. Por-Si was fabricated by electrochemical etching, and Fe₂O₃ was spin-coated on it. SEM image on surface of the por-Si sample confirmed a homogeneous macro-porous layer with Fe₂O₃ on the surface as well as inside the pores. Deposition of naturally n-type α-Fe₂O₃ onto p-type por-Si formed p–n junction reducing onset potential of water splitting. The fabricated photocatalyst heterostructure α-Fe₂O₃/por-Si/c-Si/Al was found to reduce the required bias of > 1.23 V in 0.1 M H₂SO₄ solution for both oxygen evolution and hydrogen evolution reaction. This was also confirmed from the Mott–Schottky plot of the fabricated heterostructure. The experimental results indicated that the problem of Fe₂O₃ as a photocatalyst in water splitting can be overcome with a reduced onset potential by incorporating it with a por-Si structure. Also, the fabricated “Al/c-Si/por-Si/α-Fe₂O₃” heterostructure showed good performance in low bias region (V < 0.8 V vs. V_RHE).