Harnessing the potential of cube-like Holmium doped bismuth niobate (Ho–Bi₅Nb₃O₁₅) amalgamated with rGO sheets for rapid photocatalytic elimination of crystal violet and acetylsalicylic acid

Synthesis of unique morphologies in photocatalytic materials, coupled with utilization of wide-spectrum solar energy through rare earth doping, holds significant promise to maximize the potential of photocatalysts. Herein in, cube-like Holmium (Ho) doped Bi₅Nb₃O₁₅ was synthesized by the hydrothermal method and integrated with reduced graphene oxide (rGO) sheets. As synthesized Ho–Bi₅Nb₃O₁₅@rGO composite along its analogs i.e., Bi₅Nb₃O₁₅ and Ho–Bi₅Nb₃O₁₅ was characterized by XRD, SEM, FT-IR, TGA, I–V, EIS, Mott-Schottky and photo-current measurements. Phase studies showed that crystallite size for Bi₅Nb₃O₁₅, Ho–Bi₅Nb₃O₁₅, and Ho–Bi₅Nb₃O₁₅@rGO was 27.4, 25.5, and 13.5 nm, respectively. Optical analysis exhibited a reduction in the band gap in consequent to Ho doping from 2.54 to 2.19 eV for Ho–Bi₅Nb₃O₁₅. Conductivity and photo-current measurements showed a remarkable increase in both electrical conductivity and photo-response of Ho–Bi₅Nb₃O₁₅ upon its incorporation into rGO matrix, reaching maximum values of 1.72 × 10⁻² S/m and 0.66 μA, respectively. The enhanced photocatalytic activity of Ho–Bi₅Nb₃O₁₅@rGO was ensured through the outstanding photo-degradation efficiency (96.5 %) against crystal violet (CV), greater than Bi₅Nb₃O₁₅ (49 %) and Ho–Bi₅Nb₃O₁₅ (63.4 %). Additionally, Ho–Bi₅Nb₃O₁₅@rGO showed sufficient potential towards the degradation of acetylsalicylic acid (ASA) with 79.1 % photo-degradation. This elevated photocatalytic activity of Ho–Bi₅Nb₃O₁₅@rGO is believed to be contributed by the collaborative outcomes aroused from the Ho-doping and heterojunction fabrication among cubical Ho–Bi₅Nb₃O₁₅ and rGO sheets. Hence, our work proposes an efficient strategy for the development of innovative photolytic materials for sustainable wastewater remediation.