One-pot fabrication of a double Z-scheme CeCO 3 OH/g-C 3 N 4 /CeO 2 photocatalyst for nitrogen fixation under solar irradiation

A CeCO 3 OH/g-C 3 N 4 /CeO 2 ternary photocatalyst (abbreviated as 2Ce-CN) was synthesized by a facile in situ self-sacrificing hydrothermal method, using CeCl 3 and graphitic carbon nitride (g-C 3 N 4 ) as precursors. 2Ce-CN exhibited an enhanced nitrogen photofixation activity of approximately 1.16 mM g −1 h −1 without adding any sacrificial agent, which was four times higher than that of pristine g-C 3 N 4 . The nitrogen photofixation performance was attributed to a combination of the following reasons. First, the chemical adsorption of nitrogen at Ce 3+ sites activated the NN bond. Second, photogenerated electrons in the conduction band (CB) of CeO 2 transferred to the valence band (VB) of g-C 3 N 4 , while electrons in the CB of g-C 3 N 4 transferred to the VB of CeCO 3 OH, as a result of the intimate-contact chemically-bound interface. This electron transfer is shown to be a double Z-scheme mechanism. The rate of charge carrier recombination was reduced, leaving more electrons in the CB of CeCO 3 OH to reduce the adsorbed nitrogen to ammonia. Third, the valence change between Ce 4+ and Ce 3+ in CeO 2 further promoted the nitrogen hydrogenation reaction. This simple self-sacrificing method provides an alternative perspective for designing functional g-C 3 N 4 with excellent photocatalytic activity.