Synergistic Role of Dual Metal (V) and Non‐Metal (N) Doping with Carbon Sensitization in 3D Hierarchical Nb ₂ O ₅ for Highly Selective Visible‐Light‐Driven CO ₂ ‐to‐CH ₄ Photoreduction

ABSTRACT Photocatalytic CO 2 conversion into energy‐rich fuels offers a sustainable route to address global energy and environmental challenges. However, achieving high activity and selectivity under visible light remains a key limitation. In this study, a 3D hierarchical Nb 2 O 5 nanoflower photocatalyst dual‐doped with vanadium (V), nitrogen (N), and sensitized with carbon (designated NVNBOC) is synthesized via a two‐step hydrothermal process followed by calcination. The incorporation of dual metal and non‐metal dopants, in combination with carbon sensitization, yielded a strong synergistic effect, significantly enhancing both photocatalytic performance and selectivity. Under visible‐light irradiation, the NVNBOC catalyst achieved a remarkable methane (CH 4 ) production rate of 78.32 µmol·g −1 ·h −1 , approximately 12 times higher than that of pristine Nb 2 O 5 , with an outstanding CH 4 selectivity of 97.10%. In‐situ DRIFTS results revealed that the NVNBOC photocatalyst facilitates a stepwise CO 2 reduction pathway, involving key intermediates such as *HCOO − , *CHO, and *CH 3 O, ultimately leading to full CH 4 generation. These findings demonstrate the pivotal role of dual dopant engineering in enhancing light utilization, charge separation, and intermediate stabilization, providing a promising approach for advancing visible‐light‐driven photocatalytic CO 2 reduction toward practical clean energy applications.