Exploring complex silver sulfide nano-systems as efficient photocatalysts for wastewater remediation and clean energy production: Toward sustainable and circular economy

Abstract

Essential resources like air, water, food, and energy, particularly in transportation and technology sectors, are crucial for human survival and growth. However, challenges such as industrial dye pollution in soil and water, rising atmospheric CO<inf>2</inf> levels, and fossil fuel depletion form a complex ecological system and demand urgent action. Innovations in efficient solar energy harnessing, hydrogen production, CO<inf>2</inf> conversion to valuable chemicals, and eco-friendly dye degradation methods are critical for achieving sustainability. Multifunctional nanoparticles, especially metal sulfides, have gained attention due to their cost-effectiveness and appropriate band alignment of metal sulfides for solar fuel generation. Among them, silver sulfide (Ag<inf>2</inf>S)-based nanomaterials stand out owing to narrow and tunable bandgaps and broad visible-light absorption. This review critically examines recent progress in Ag<inf>2</inf>S-based nano-photocatalysts for dual applications: wastewater treatment and energy generation. It focuses on advanced engineering strategies like heterojunction formation and doping to enhance photocatalytic efficiency, stability, and selectivity. Additionally, it discusses the synergistic role of Ag<inf>2</inf>S nanocomposites in degrading organic pollutants for wastewater remediation and promoting hydrogen evolution/CO<inf>2</inf> reduction for clean energy. The potential integration of these nano-photocatalysts into scalable systems aligned with circular economy principles is explored, emphasizing resource recovery, environmental sustainability, and low-carbon technologies. Current challenges, alternative strategies, and future directions are also highlighted to guide the development of next-generation Ag<inf>2</inf>S-derived photocatalysts for environmental and energy applications for human welfare and the growth of society.