Ferrites boosting photocatalytic hydrogen evolution over graphitic carbon nitride: a case study of (Co, Ni)Fe₂O₄ modification

The charge carrier separation and surface catalytic redox reactions are of primary importance as elementary steps in photocatalytic hydrogen evolution. In this study, both of these two processes in photocatalytic hydrogen evolution over graphitic carbon nitride (g-C₃N₄) were greatly promoted with the earth-abundant ferrites (Co, Ni)Fe₂O₄ modification. CoFe₂O₄ was further demonstrated to be a better modifier for g-C₃N₄ as compared to NiFe₂O₄, due to the more efficient charge carrier transfer as well as superior surface oxidative catalytic activity. When together loading CoFe₂O₄ and reductive hydrogen production electrocatalyst Pt onto g-C₃N₄, the obtained Pt/g-C₃N₄/CoFe₂O₄ photocatalyst achieved visible-light (λ > 420 nm) hydrogen production rate 3.5 times as high as Pt/g-C₃N₄, with the apparent quantum yield reaching 3.35 % at 420 nm.