Boosted Photoelectrochemical Water Oxidation Performance with a Quaternary Heterostructure: CoFe[sub.2]O[sub.4]/MWCNT-Doped MIL-100/TiO[sub.2]

Cobalt ferrite (CoFe[sub.2]O[sub.4]) combined with multi-walled carbon nanotubes (MWCNTs) is an outstanding material regarding photoelectrochemical water oxidation (PEC-WO) because of its excellent catalytic properties and stability. On the other hand, surface imperfections in CoFe[sub.2]O[sub.4] can cause band bending and surface Fermi level pinning, significantly reducing its PEC conversion efficiency. Heterostructure engineering is essential for achieving increased light-gathering capacity and charge separation efficiency for PEC-WO. In this study, a quaternary heterostructure of CoFe[sub.2]O[sub.4]/MWCNT-doped Metal–Organic Framework-100 (Iron), MIL-100(Fe)/Titanium Oxide (TiO[sub.2]) was synthesized by using a combination of hydrothermal, solvothermal, and “dip and dry” techniques. Characterization results confirmed the formation of a structural network of MIL-100(Fe) on TiO[sub.2] surfaces, enhanced by the incorporation of MWCNTs during the hydrothermal reaction. Under 1 sun irradiation, the resultant quaternary heterostructure displayed a photocurrent density (J [sub.ph]) of 3.70 mA cm[sup.−2] under free bias voltage, which is around 3.08 times more than that of pristine TiO[sub.2] photoanodes (J [sub.ph] = 1.20 mA cm[sup.−2]). This investigation highlights the advantages of the MIL-100(Fe) network in improving the solar PEC-WO performance of TiO[sub.2] photoanodes.