Synergetic dual co-catalyst and interfacial bonds in N-CQDs/NCN/BNQDs to promote photoremoval of uranium(VI)

Abstract

The photocatalytic efficiency of a catalyst is dependent on two main factors: the separation of excitons and the migration of photogenerated carriers. Therefore, we employed a strategy of defect engineering, co-catalyst co-modification and interfacial chemical bonding synergistic modification to prepare N-CQDs-x/NCN/BNQDs-y by introducing nitrogen defects in graphitic carbon nitride (NCN) and concomitantly incorporating boron nitride quantum dots (BNQDs) and nitrogen-doped carbon quantum dots (N-CQDs) onto its surface. And the N-CQDs-₁₅/NCN/BNQDs-₁ showed excellent photocatalytic removal of U(VI), which achieved 98.7 % after 120 min of illumination. Furthermore, the catalytic activities were ranked as follows: N-CQDs-₁₅/NCN/BNQDs-₁ > N-CQDs-₁₅/NCN > NCN/BNQDs-₁ > NCN > g-C₃N₄. Systematic investigations unveiled that the improved catalytic performance of N-CQDs-₁₅/NCN/BNQDs-₁ was mainly attributed to the nitrogen defects in g-C₃N₄ facilitating carrier separation, the C–C interface bonding between N-CQDs and g-C₃N₄ and the hydrogen bonding between BNQDs and g-C₃N₄, as well as co-catalysts transferring electrons and holes, respectively, promoting the simultaneous transfer of e^- and h⁺. Simultaneously, the prepared photocatalytic materials exhibited outstanding cyclic stability, with the U(VI) removal rate by the catalyst remaining above 91 % after five consecutive photocatalytic experiments. This study not only presents an effective photocatalytic material for the remediation of uranium-containing wastewater but also offers insights into the design of efficient photocatalysts.