Nb 掺杂调控 BaTiO₃/g-C₃N₄ 异质结光催化产氢

Niobium-doped barium titanate/carbon nitride heterojunction for enhanced photocatalytic hydrogen production

摘要

利用太阳能驱动半导体光催化分解水制氢被认为是一种绿色、可持续的制氢途径，其关键在于构筑兼具高活性与低成本的光催化材料体系. BaTiO₃（BTO）因其无毒、成本低，结构稳定等优势受到关注，但其宽禁带特性导致可见光响应受限，同时光生载流子分离效率较低，严重制约其光催化实际应用潜力. 针对上述问题，本文提出将 Nb 掺杂与类核–壳异质结构筑相结合的策略，对 BTO 的能带结构与界面电荷行为进行协同调控，以期实现低成本、高效光解水制氢的目的. 结果表明，适量 Nb 掺杂（2%）可诱导 BTO 导带位置负移，并有效改善体相载流子传输特性. 该作用增强了材料的光还原能力，使其光催化产氢速率提升至 1535.3 μmol·g⁻¹·h⁻¹，约为未掺杂 BTO 的 4.6 倍. 进一步通过在 Nb–BTO 表面构筑 Nb–BTO/CN 类核–壳异质结，实现能带结构优化并显著拓宽光吸收范围. Nb–BTO/CN 间形成的 S 型异质结与内建电场协同作用，有效促进材料体相及界面处光生载流子的分离与传输，并保持了空间分离的电子和空穴的最大氧化还原能力. 该复合催化剂的产氢速率达到 2993.9 μmol·g⁻¹·h⁻¹，分别为纯 BTO 和 Nb–BTO 的 9.2 倍和 2.0 倍. 综合结果表明，Nb 掺杂与 CN 类核–壳异质结工程在 BTO 能带调控与界面载流子动力学方面具有显著协同效应：Nb 掺杂诱导 BTO 导带负移并改善结晶度；与 CN 构筑的 S 型异质结进一步优化电荷迁移动力学并增强还原驱动力，二者协同最终显著提升材料的光催化产氢性能. 该工作为钛酸盐基光催化制氢体系的理性设计提供了新的材料构筑思路与实验依据.

Abstract

Solar-driven semiconductor photocatalytic water splitting for hydrogen production is regarded as a green and sustainable approach to address energy and environmental challenges. However, traditional wide-bandgap semiconductor photocatalysts generally suffer from insufficient visible-light response and rapid photogenerated charge carrier recombination, leading to relatively low solar-to-hydrogen conversion efficiency. Therefore, the construction of photocatalytic material systems that combine high activity with low cost has become a critical scientific issue in this field. BaTiO₃ (BTO) has attracted considerable attention owing to its nontoxicity, low cost, and robust structural stability. Nevertheless, its wide bandgap limits its visible-light response, and inefficient separation and transport of photogenerated charge carriers severely restrict its photocatalytic performance. To address these issues, this study proposes a synergistic strategy combining Nb doping with a core–shell-like heterojunction construction to systematically regulate the band structure and interfacial charge behavior of BTO, aiming to achieve low-cost and efficient photocatalytic water splitting for hydrogen production. The chemical structure and morphology of the as-prepared materials were systematically characterized using multiple techniques, followed by a comparative evaluation of photocatalytic performance and an in-depth analysis of the hydrogen production mechanism. The results demonstrate that an appropriate Nb doping level (2%) induces a negative shift in the conduction band edge and significantly improves bulk charge transport, thereby enhancing the photoreduction capability and increasing the hydrogen production rate to 1535.3 μmol·g^–1·h^–1, which is approximately 4.6 times that of pristine BTO. Subsequently, a Nb–BTO/CN core–shell-like heterojunction was constructed on the surface of Nb–BTO. This configuration optimizes the energy band alignment and markedly broadens the light absorption range. The formation of an S-scheme heterojunction between Nb–BTO and carbon nitride (CN), together with the built-in electric field at the interface, significantly promotes the spatial separation and directional migration of photogenerated charge carriers both within the bulk phase and across the heterointerface. In this S-scheme system, the internal electric field drives electrons from the CN conduction band to recombine with holes from the Nb–BTO valence band while preserving the highly energetic electrons in the Nb–BTO conduction band for efficient proton reduction. Importantly, this configuration preserves the maximum redox capability of the spatially separated electrons and holes. Consequently, the hydrogen production rate of the resultant composite photocatalyst reaches 2993.9 μmol·g⁻¹·h⁻¹, corresponding to 9.2 times and 2.0 times that of pristine BTO and Nb–BTO, respectively. The results demonstrate the synergistic effects of Nb doping and CN core–shell-like heterojunction engineering on energy band modulation and interfacial charge carrier dynamics in BTO-based photocatalysts. Specifically, Nb doping shifts the conduction band edge of BTO toward a more negative potential and improves crystallinity as well as bulk carrier transport characteristics. Meanwhile, the S-scheme heterojunction constructed with CN further refines the charge transfer kinetics and enhances the thermodynamic driving force for reduction reactions. The synergy arises from the fact that Nb doping optimizes the bulk properties of BTO, while the CN shell extends light absorption and facilitates interfacial charge separation. Collectively, these synergistic modifications substantially enhance photocatalytic hydrogen production performance. This work provides a rational material design strategy and an experimental basis for constructing high-efficiency titanate-based photocatalytic hydrogen generation systems and offers new insights into the cooperative use of elemental doping and heterojunction engineering in wide-bandgap oxide photocatalysts.

关键词

Nb 掺杂钛酸钡 / 氮化碳 / 能带结构调控 / S 型异质结 / 光催化产氢

Key words

niobium-doped barium titanate / carbon nitride / band structure modulation / S-scheme heterojunction / photocatalytic hydrogen production

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基金资助

国家自然科学基金项目(62004084)

国家自然科学基金项目(22106053)

江苏大学高层次人才基金(23JDG011)

江苏大学高层次人才基金(23JDG012)