Advanced CeO₂-Based Heterojunctions: Aspects of Structure–Function Relationships for Sustainable CO₂ Conversion and H₂ Production

Abstract

The rising global energy demand and climate crisis have intensified the need for sustainable technologies to mitigate carbon emissions while enabling renewable energy conversion. Photocatalysis, particularly using solar energy, has emerged as a promising green solution for hydrogen production and CO₂ reduction. Among various semiconductor photocatalysts, cerium oxide (CeO₂) has garnered considerable interest due to its favourable properties, including strong redox capability, high oxygen storage capacity, chemical stability, and earth abundance. However, intrinsic drawbacks such as a wide band gap, limited visible-light absorption, and rapid charge recombination restrict its standalone performance. This review comprehensively examines recent advancements in CeO₂-based photocatalysts, focusing on structural modifications and the formation of heterojunctions, including S-scheme, Type II, and Z-scheme architectures, that enhance charge separation and retain redox potential. Fabrication strategies are broadly classified into bottom-up and top-down methodologies, with particular emphasis on techniques such as sol–gel, hydrothermal, and co-precipitation methods, which are comprehensively discussed for their effectiveness in optimizing morphology and surface activity. Furthermore, the integration of CeO₂ with advanced materials (e.g. g-C₃N₄, Ti₃C₂, Metal–organic frameworks (MOFs)) and defect engineering approaches is highlighted for improving photocatalytic efficiency under solar irradiation. Promising applications in photocatalytic reduction of CO₂ to value-added chemicals and solar-driven catalytic hydrogen evolution are explored. The review also outlines current challenges, such as poor selectivity, low photostability, and scalability, and provides future perspectives on rational design, real-world testing, and eco-friendly fabrication routes to accelerate the deployment of CeO₂-based photocatalytic systems.

Graphical Abstract

Keywords

CeO₂ / Photocatalyst / S-scheme / Heterojunction / Energy conversion

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