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

Abstract

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. VRHE).