Interaction between HCHO molecule and B, Zn co-doped g-C3N4 surface: A DFT study

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The interaction between formaldehyde (HCHO) and B, Zn co-doped g-C3N4 surface was studied using density functional theory calculation. Compared with previous study for HCHO adsorption on un-doped surface, it was found that the doping of B, Zn increases the active sites of HCHO degradation in g-C3N4 surface, which changes from one of un-doped surface to three of doped surface. In these three adsorption configurations, the interactions between HCHO and B, Zn co-doped g-C3N4 surface are all very strong, which leads to the dramatic change of doped surface structure. Therefore, the calculated adsorption energies of three configurations (MA,-1.159eV; MB, -1.084eV; MC, -0.898 eV) are much larger than that of HCHO on the surface of pure g-C3N4 (-0.213 eV). HCHO molecules are dissociated in all three models with the break of two C–H bonds. The two broken hydrogen atoms are bonded to two nitrogen atoms of the surface to form H–N bonds, respectively. The charge transfers from HCHO molecules to B, Zn co-doped g-C3N4 surface in three systems (MA, 0.347 e; MB, 0.562 e; MC, 0.489 e), and the hydrogen and oxygen atoms of HCHO are electron donors, while doping atoms (B and Zn) of surface are major acceptors.