Water splitting has the potential to revolutionize the energy industry by providing efficient H2 production. But, the low efficiency and high cost associated with the current catalyst have hindered its large-scale implementation. Recently, 2D materials have emerged as promising candidates for catalyzing water splitting due to their unique electronic and structural properties. Here, we investigate the confinement and heterointerface reconstruction in 2D materials as a strategy to further improve their catalytic performance for water splitting to enhanced charge transfer, resulting in improved water splitting performance. Moreover, we show that the heterointerfaces can trigger water oxidation catalysis by providing active sites for OER. Our results indicate that the heterointerface reconstruction in 2D materials is a promising approach to enhance their catalytic activity for green hydrogen production. The insights gained from this study can pave the way for the rational design and engineering of 2D materials for efficient energy conversion.