Z-scheme Bi₂SiO₅/Ni-doped Ag₆Si₂O₇ heterojunction with remarkable photocatalytic performance for MO degradation with enhanced light absorption ability: Adjustment of electron transfer path and energy band structure

In this paper, a novel Bi₂SiO₅/Ni-Ag₆Si₂O₇ semiconductor with remarkable light absorption ability and electron transfer efficiency was synthesized through ice bath deposition and hydrothermal method. The addition of Ni²⁺ reduced the particle size of Ag₆Si₂O₇ and increased specific surface area. Under simulated sunlight, the degradation rate of the optimal samples for MO reached 0.03743 min⁻¹, which was 7.28 times, 3.15 times and 1.56 times than that of Bi₂SiO₅ and Ag₆Si₂O₇ and Bi₂SiO₅/Ag₆Si₂O₇, respectively. The formation of Z-scheme heterojunction inhibited the photoinduced carrier recombination, promoted the generation of active free radicals and preserved high redox capacity of photogenerated carriers. According to the density functional theory (DFT) and M-S test, an intermediate doping energy level was introduced to Ag₆Si₂O₇, which acted as the capture center of photogenerated carriers and effectively adjusted the energy band structure. The impurity energy level further inhibited the recombination of carriers and promoted the electron transfer in the Z-scheme transfer mechanism. Moreover, the introduction of Ni²⁺ further enhanced the light response of photocatalysts. Therefore, the improved photocatalytic ability was assigned to the introduction of Ni²⁺ ions based on the formation of heterojunction.