Abstract: Solar-driven semiconductor photocatalytic water splitting for hydrogen production is regarded as a green and sustainable approach, in which the key lies in the development of photocatalysts with both high activity and low cost. BaTiO? (BTO) has attracted considerable attention owing to its non-toxicity, low cost and structural stability; however, its wide band gap results in limited visible-light response and inefficient separation and transport of photogenerated charge carriers, severely restricting its photocatalytic performance. To address these issues, a synergistic strategy combining Nb doping and core–shell heterojunction construction is proposed to systematically regulate the band structure and interfacial charge behavior of BTO. The results demonstrate that appropriate Nb doping induces a negative shift of the conduction band and significantly improves bulk charge transport, thereby enhancing the reduction capability of BTO and increasing the hydrogen evolution rate to 1535.3 μmol·g-1·h-1, which is approximately 4.6 times that of pristine BTO. Furthermore, by constructing a Nb-BTO/CN core–shell heterojunction on the surface of Nb-BTO, the band structure is further optimized and the light absorption range is remarkably broadened, leading to a substantially enhanced hydrogen evolution rate of 2993.9 μmol·g-1·h-1, which is about 9.2 and 2.0 times higher than those of pristine BTO and Nb-BTO, respectively. Comprehensive analyses reveal that Nb doping and core–shell heterojunction engineering generate a pronounced synergistic effect in band structure modulation and interfacial charge carrier dynamics, thereby significantly improving the photocatalytic hydrogen evolution performance of BTO-based materials. This work provides a rational material design strategy and experimental basis for the development of efficient titanate-based photocatalytic hydrogen production systems.