Hierarchical Si x Zr 1− x MgO Monolithic Heterojunctions for Efficient Photocatalytic Hydrogen Evolution

The production of green hydrogen (H 2 ) is a sustainable approach to addressing the current energy crisis without contributing to long‐term greenhouse gas emissions. Many semiconductors based photocatalysts have shown great promise for light‐driven H 2 generation. However, nanostructured powder form suffers from slow electron transfer kinetics, material loss, poor recyclability, and non‐uniform light distribution, resulting in inconsistent hydrogen production performance. In this work, interface‐mediated hierarchical heterojunctions, designed as a stable and efficient photocatalytic scaffold for solar hydrogen production and investigate their performance and structural stability by examining a series of Si x Zr 1− x MgO photocatalysts. A hydrogen generation yield of 694 μmol cm −2 h −1 was obtained for Si 0.9 Zr 0.1 MgO which is approximately 9 times higher than that of Si 0.1 Zr 0.9 MgO (76 μmol cm −2 h −1 ). The system maintained high H 2 production activity after 7 h of irradiation, demonstrating excellent stability and potential for practical applications. The enhanced photocatalytic performance of Si 0.9 Zr 0.1 MgO is attributed to its oxygen‐vacancy‐rich heterojunction structure, which improves visible‐light absorption, facilitates charge separation, and accelerates interfacial electron transfer, thereby promoting efficient photocatalytic H 2 evolution. The concept of interface‐mediated hierarchical heterojunctions introduces a novel strategy for structural and functional optimization in multi‐component photocatalysts. This work highlights a promising strategy for designing next‐generation, earth‐abundant photocatalysts for scalable solar‐to‐hydrogen conversion applications.