Combined metal ferrite oxide photoanodes and photocathodes for unassisted sunlight-driven tandem photoelectrochemical cells

Metal ferrite oxide (MFe2O4) and iron oxide (Fe2O3) were explored as an unassisted operation for the solar light harvesting photoelectrochemical cell (PEC). The metal ferrite oxides studied in this work were CuFe2O4, NiFe2O4, and ZnFe2O4 which were synthesized by the electrochemical deposition method. The crystal structure, surface morphology, and chemical species of the Fe2O3 and metal ferrite oxides were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spec-troscopy. The result showed that the CuFe2O4 exhibited the p-type semiconductor characteristic while the Fe2O3, NiFe2O4, and ZnFe2O4 exhibited the n-type semiconductor characteristic. Thus, the coupling between the n-type and p-type semiconductors can form the PEC without external bias. As a result, the CuFe2O4 was set as the photocathode while the others were set as the photoanode. The parallel and general tandem photo-electrochemical configurations were investigated. All materials can be used as the unbiased PEC, and the highest performance is the Fe2O3 coupled with the CuFe2O4. The maximum photocurrent of the Fe2O3-CuFe2O4 tandem PEC is similar to 6 mu A/cm(2) in the parallel illumination.

Automated summary

Metal ferrite oxides (MFe2O4) and iron oxide (Fe2O3) were investigated as unassisted operation for solar light harvesting photoelectrochemical cell (PEC). Different metal ferrite oxides, such as CuFe2O4, NiFe2O4, and ZnFe2O4, were synthesized using electrochemical deposition method. The crystal structure, surface morphology, and chemical composition of Fe2O3 and metal ferrite oxides were characterized using various techniques. CuFe2O4 showed p-type semiconductor characteristic, while Fe2O3, NiFe2O4, and ZnFe2O4 exhibited n-type semiconductor characteristic. Therefore, the coupling between n-type and p-type semiconductors can form PEC without external bias. CuFe2O4 was set as the photocathode, and the others were set as the photoanode. Both parallel and tandem configurations were explored. All materials can be used as unbiased PEC, and the best performance was observed with Fe2O3 coupled with CuFe2O4. The maximum photocurrent of Fe2O3-CuFe2O4 tandem PEC was around 6 mu A/cm(2) under parallel illumination conditions.