One-pot fabrication of a double Z-scheme CeCO3OH/g-C3N4/CeO2 photocatalyst for nitrogen fixation under solar irradiation

A CeCO 3 OH/g-C3N4/CeO2 ternary photocatalyst (abbreviated as 2Ce-CN) was synthesized by a facile in situ self-sacrificing hydrothermal method, using CeCl3 and graphitic carbon nitride (g-C3N4) 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-C3N4. The nitrogen photofixation performance was attributed to a combination of the following reasons. First, the chemical adsorption of nitrogen at Ce3+ sites activated the N. N bond. Second, photogenerated electrons in the conduction band (CB) of CeO2 transferred to the valence band (VB) of g-C3N4, while electrons in the CB of g-C3N4 transferred to the VB of CeCO3OH, 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 CeCO3OH to reduce the adsorbed nitrogen to ammonia. Third, the valence change between Ce4+ and Ce3+ in CeO2 further promoted the nitrogen hydrogenation reaction. This simple self-sacrificing method provides an alternative perspective for designing functional g-C3N4 with excellent photocatalytic activity.