Non-Metallic Doping of Multinary Metal Oxide Semiconductors for Energy Applications

Multinary metal oxides are widely applied in energy storage and conversion, heterogeneous catalysis and environmental technologies, but their wide band gaps, low intrinsic electronic conductivity and limited density of active sites severely restrict their practical efficiency. This review examines non-metallic doping via the substitutional, interstitial or mixed incorporation of light elements such as B, C, N, F, P and S as a versatile strategy to overcome these fundamental limitations. We begin by outlining the primary synthesis methodologies for doped oxides, such as sol–gel, chemical vapor deposition, and hydrothermal routes, followed by a critical discussion of the multi-technique characterization framework required to verify successful dopant incorporation and elucidate its structural and electronic consequences. We focus on the fundamental principles of how doping parameters—such as mode, element type, and concentration—can be tuned to regulate material properties. The key mechanisms for performance enhancement, including synergistic lattice reconstruction, defect engineering, and electronic structure modulation, are emphasized. Significant advancements are highlighted in applications like energy storage, fuel cells, water splitting, and CO2 reduction. Finally, we assess current challenges, such as the precise control of doping sites and long-term stability, and offer perspectives on the rational design of next-generation oxide materials.