In situ construction of CuFe2O4/CuO heterojunction photocathode for improved solar water splitting

CuFe₂O₄ is considered to be a prospective photocathode candidate due to its suitable optical bandgap and visible light response characteristics. However, its poor charge carrier transport capability severely restricts the photocatalytic performance. In this study, a CuFe₂O₄/CuO heterojunction photoelectrode was in situ constructed via spray pyrolysis for the first time, significantly enhancing photoelectrocatalytic performance. The key physical and photophysical properties of CuFe₂O₄, CuO, and CuFe₂O₄/CuO heterojunction thin films were systematically analyzed and evaluated. Experimental results demonstrate that the optimized CuFe₂O₄/CuO attains a net photocurrent density of 17 μA/cm² under 0.7 V vs. RHE, exhibiting a 2.6-fold enhancement over pristine CuFe₂O₄. This indicates that the heterojunction effectively accelerates the separation of photogenerated charges and boosts catalytic reaction efficiency. Further comparison between CuFe₂O₄/CuO and CuO/CuFe₂O₄ bilayer heterojunctions reveals that the latter exhibits increased dark current and no significant photocurrent enhancement due to interfacial band mismatch, confirming the critical role of in situ heterojunction growth in optimizing interfacial charge transport. This study offers novel perspectives on constructing metal oxide heterostructure photoelectrodes through band engineering.