Titanium dioxide (TiO₂) is a promising photocatalyst for the hydrogen evolution reaction owing to its chemical stability and low cost. However, pristine TiO₂ suffers from insufficient light absorption and rapid charge recombination, severely constraining its efficiency. Although oxygen vacancy (O_V) extends light absorption and optimizes thermodynamic/kinetic conditions, they may function as recombination centers that compromise carrier separation. Constructing multiphase interfaces offers an effective way to overcome this constraint. In this work, we synergize O_V optimization and multiphase interface engineering in TiC/TiO₂ heterostructures to ensure abundant active sites while enhancing charge dynamics. The photocatalyst delivers 1646 μmol·h⁻¹·g⁻¹ H₂ under simulated AM1.5G illumination. This performance enhancement arises from three cooperative mechanisms: (i) abundant O_V formed during plasma pyrolysis provides reactive sites for proton adsorption; (ii) TiC broadens light absorption regions; and crucially, (iii) multiphase interfaces among rutile (R-TiO₂), anatase TiO₂ (A-TiO₂) and TiC establish directional charge-transfer channels that promote carrier dissociation. This study demonstrates that integrating thermal plasma synthesis with controlled oxidation provides a versatile design strategy for multiphase interface engineering efficient photocatalysts toward photocatalytic hydrogen production.