Advances in Co3O4 nanomaterial-based photocatalysts for water purification: mechanisms, green synthesis, activation of oxidants, waste-derived sources, and computational insights

Abstract

Water scarcity remains a critical global challenge, affecting billions of people and significantly impacting ecosystems, economies, and public health. Among various water treatment technologies, photocatalysis has emerged as a highly effective method for degrading a wide range of contaminants. Cobalt oxide (Co₃O₄) has gained considerable attention as a photocatalyst due to its unique structural, electronic, and optical properties. Despite extensive research on the synthesis and application of Co₃O₄-based photocatalysts, a comprehensive review summarizing recent advancements and modifications in Co₃O₄ nanomaterials over the past five years is notably lacking. This review critically examines the fundamental photocatalytic mechanisms of Co₃O₄ nanomaterial-based systems, systematically discussing their advantages and inherent limitations. Additionally, it explores emerging research trends, including biosynthesis, facile recovery, synthesis from waste-derived sources, and computational techniques, alongside the prevailing challenges shaping this field. Furthermore, the review identifies key research directions for the future development and optimization of Co₃O₄-based nanostructures, emphasizing their potential to enhance photocatalytic efficiency for water purification. By addressing these aspects, this work aims to bridge existing knowledge gaps and provide a foundation for future innovations in sustainable water treatment technologies.

Fig. 1. Co₃O₄ nanomaterial-based photocatalysts with varied morphologies in the application for water treatment in the recent five years: nanosheet Co₃O₄ (ref. 33) (a), mesoporous Co₃O₄ (ref. 34) (b), quantum dot Co₃O₄ (ref. 35) (c), polyhedral Co₃O₄ (ref. 38) (d), and cubic Co₃O₄ (ref. 37) (e). Reprinted with permission from ref. Copyright (2019), ref. Copyright (2023), ref. Copyright (2022), ref. Copyright (2022), and ref. Copyright (2024), with permission from Elsevier.

Fig. 2. Biosynthesis of Co₃O₄ nanoparticles from Piper betle extract for photocatalytic degradation of Eriochrome Black T: synthesis process (a), electronic structure (b), and photocatalytic performance in degradation of Eriochrome Black T (c). Reprinted with permission from ref. , Copyright (2022), with permission from Elsevier.

Fig. 3. Photocatalytic mechanism of the Co₃O₄ nanomaterial-based composites: Straddling type-I heterojunction system of rGO-Co₃O₄/ZnO composite (a), type-II and p–n heterojunction system of Co₃O_4(QDs)/Bi₂WO₆ composite (b), and dual Z-scheme system of Co₃O₄/MoS₂/SrTiO₃ composite (c). Reprinted with permission from ref. Copyright (2023), ref. Copyright (2022), ref. Copyright (2024) with permission from Elsevier.

Fig. 4. Magnetization curve (a), molecular dynamics simulation for the adsorption of O₂ on two components of the composite (b), and photocatalytic mechanism of the Ag/Co₃O₄/NiFe₂O₄ photocatalytic system (c). Reprinted with permission from the ref. Copyright (2022) with permission from Elsevier.

Fig. 5. Photocatalytic activation mechanism of oxidants by Co₃O₄ (ref. 53) (a), Co₃O₄/g-C₃N₄ (ref. 31) (b), and Co₃O₄@P–C₃N₄/α-Fe₂O₃ (ref. 54) (c). Reprinted with permission from the ref. Copyright (2024), ref. Copyright (2021), and ref. Copyright (2024) with permission from Elsevier.

Fig. 6. The calculated density of states for (a) TiO₂ and (c) Co₃O₄, alongside the electrostatic potential for (b) TiO₂ and (d) Co₃O₄. Panel (e) depicts the built-in electric field formed at the TiO₂/Co₃O₄ interface. Reprinted with permission from the ref. , Copyright (2020) with permission from Elsevier.

Van Dien Dang

Nguyen Thi Hong Nhung

Iqra Rabani

Nguyen Tien Tran

Bui Thi Phuong Thuy

Hai Bang Truong