Hg0 to Hg2+ via photocatalysis by Bismuth-based photocatalysts: A review

Abstract

Photocatalytic oxidation technology offers environmental friendliness, wide application range, and low energy consumption, playing a crucial role in balancing energy and environmental concerns. Bismuth-based photocatalysts, due to their unique electronic structures and tunable micro-morphologies, exhibit significant advantages in the photocatalytic oxidation of Hg⁰. These photocatalysts convert elemental mercury (Hg⁰), which is difficult to remove, into oxidized mercury (Hg²⁺), which is easier to adsorb and remove. However, conventional Bi-based photocatalysts often face issues such as wide band gaps, high excitation energy, and rapid recombination of photogenerated charge carriers, which limit their photocatalytic performance. This review summarizes various modification strategies for bismuth-based semiconductors, including heterojunction construction, doping, and surface defect engineering, to enhance their mercury removal efficiency. Additionally, it covers different synthesis methods for bismuth-based catalysts and their photocatalytic performance, and reveals the materials' band gap widths and density of states (DOS) through density functional theory (DFT) calculations. Finally, the review explores the future prospects of bismuth-based photocatalysts, aiming to provide practical guidance for the development of novel, efficient Bi-based photocatalysts, offering theoretical support for the implementation and advancement of the Minamata Convention on Mercury.