In-situ self-sacrificial fabrication of lanthanide hydroxycarbonates/graphitic carbon nitride heterojunctions: nitrogen photofixation under simulated solar light irradiation

Abstract

LnCO3OH/g-C3N4 (named LnCN, LnLa, Pr) heterojunction was synthesized with a facile in-situ hydrothermal method by self-sacrificing a part of g-C3N4 as anion source. The photocatalytic activity of LnCN heterojunction was evaluated by nitrogen photofixation under simulated solar light irradiation. The result displayed that LnCN exhibited considerable improvement in nitrogen photofixation compared to g-C3N4 and LnCO3OH. Strong nitrogen adsorption energy offered by chemical adsorption ensure that more nitrogen was adsorbed and activated on the surface of LnCN. Moreover, in LnCN Z-scheme heterojunction, the electron at CB of LnCO3OH transferred to VB of g-C3N4 through the LnN interface channel. The recombination rate of charges carriers was reduced, leaving more electron at CB of g-C3N4 to reduce the adsorbed nitrogen. Results from time-resolved PL, photocurrent, and EIS characteristics further proved LnCN showed low recombination rate of photogenerated charges carriers. Finally, the stability of LnCN was certified to be excellent, which is significant for practical application. This study presents a simple self-sacrificial method to synthesize LnCO3OH/g-C3N4 heterojunction, which can be extended to the fabrication of other g-C3N4-based heterojunction.