Preparation of double-layered Co−Ci/NiFeOOH co-catalyst for highly meliorated PEC performance in water splitting

The cobalt−carbonate (CoCi)/NiFeOOH double-layer co-catalyst was prepared on bismuth vanadate (BiVO 4 ). Compared with the same type of electrode (Co−Pi/NiFeOOH/BiVO 4 and Co−Sil/NiFeOOH/BiVO 4 ), the photoelectrochemical (PEC) performance of the composite electrode presents the most excellent performance. The Co−Ci/NiFeOOH/BiVO 4 electrode prepared by photoelectric deposition (PED) achieves a photocurrent density of 4.1 ​mA/cm 2 at 1.23 ​V vs RHE, and the applied bias photon-current efficiency (ABPE) is up to 0.95%. In addition, with the help of the equivalent circuit fitting in electrochemical impedance spectroscopy (EIS), the charge transfer resistance ( R ct ) of Co−Ci/NiFeOOH/BiVO 4 is only 108.9 ​Ω, which is 16% that of BiVO 4 . The enhanced PEC performance of Co−Ci/NiFeOOH/BiVO 4 in the double-layer cocatalyst system is attributed to the outstanding advantages of Co−Ci cocatalyst in oxygen vacancy defects, superior to other cobalt-based catalysts in promoting charge transfer and improving the kinetics of water oxidation. This makes Co−Ci co-catalyst become one of the favorable competitors in the field of photoelectric catalysis.