Synergistic Effect of Hcl and Hno3 on Optical Structure of Phosphorus-Doped G-C3n4

Student: Zainab Mahmoud Shafi'i (Project, 2025)
Department of Pure and Industrial Chemistry
Bayero University, Kano, Kano State

Abstract

Catalysts generally speed up the rates of reactions. Doping enhances the properties of g-C3N4, the synergistic effects of HCl and HNO₃ treatment on the optical and structural properties of P-doped g-C₃N₄ for enhanced photocatalytic activity was done through acid modification (single and dual treatments), the samples were analyzed using FTIR (functional group identification) and UV-Vis DRS (bandgap/absorption studies). The results reveal that HCl + HNO₃ dual treatment improves structural properties. Only HNO₃ treatment induces optical enhancement with 673 nm absorption peak (attributed to NO₃⁻-derived mid-gap states). The dual-acid treatment shows no synergistic optical improvement, likely due to competitive adsorption between Cl⁻ and NO₃⁻ species, neutralizing electronic effects. These findings highlight that HNO₃ alone enhances visible-light absorption, the HCl+HNO₃ combination primarily optimizes structural properties, suggesting that sequential acid treatments may be necessary for optical-structural improvements. This work provides insights for designing acid-modified g-C₃N₄ photocatalysts with enhanced properties.

Keywords
P-doped g-C3N4 Graphitic carbon nitride HNO3 treatment HCl treatment Optical properties Stuctural properties
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