Enhanced boron modified graphitic carbon nitride for the selective photocatalytic production of benzaldehyde

Abstract

Graphitic carbon nitride is a non-metal photocatalyst easily prepared from nitrogen organic compounds through green synthesis processes that do not require the use of solvents. This work proposes the use of boron to modify the layered g-C3N4 structure by incorporating B to induce defects aimed at the enhancement of the photocatalytic activity. Boron-modified graphitic carbon has been obtained using elemental B and NaBH4 as precursors. The XRD and FTIR characterization results suggest that the C and N positions of g-C3N4 can be replaced by B, resulting in a layered modified structure in which the tri-s-triazine units are altered. The exchange of B atoms differed from the boron precursor according to the analysis of the chemical properties of the surface. Thus, the elemental B had a preference to exchange positions with N atoms, whereas the use of NaBH4 led to the substitution of B into the C positions. This difference considerably affected the photocatalytic activity during the selective oxidation of benzyl alcohol. The sample modified with NaBH4 led to the highest oxidation rate and selectivity linked to a lesser recombination effect than the other samples according to photoluminescence tests. This work provides evidence about the convenience of the selection of precursors during the modification of g-C3N4. The photon absorbance rate was determined for the estimation of the quantum yield. Although the photon absorbance rate was quite similar in all the cases, the different registered kinetics led to a maximum quantum efficiency of 0.15% for NaBCN.