Thermally Programmed Synthesis of MoS ₂ Quantum Dot/a-TiO ₂ Heterostructure for Selectively Enhanced Photo- or Electrocatalytic Hydrogen Evolution

Engineering quantum dot (QD) heterostructures with controlled interfaces is critical for advancing catalytic nanomaterials. Here, we introduce a thermally programmed recrystallization strategy, termed the selective catalysis activation protocol (SCAP), to engineer molybdenum disulfide (MoS₂) QDs within an amorphous TiO₂ (a-TiO₂) matrix. This mild, low-temperature approach enables the a priori selection of catalytic functions at the synthesis stage: lower annealing temperatures yield ultrasmall MoS₂ QDs with strong S-O-Ti-like interfacial bonding that optimize electrocatalytic hydrogen evolution, whereas higher temperatures produce QD/a-TiO₂ heterojunctions with efficient charge separation for superior photocatalysis. Comprehensive spectroscopic and microscopic analyses reveal that defect-assisted recrystallization, interfacial bond density, and quantum confinement effects collectively govern catalytic outcomes. The novelty of this study lies in demonstrating a single-material system where catalytic pathways can be rationally programmed by a simple thermal protocol. Beyond advancing hydrogen evolution catalysis, SCAP establishes a versatile and energy-efficient framework for designing QD-oxide heterostructures, offering a broadly applicable platform for catalytic nanomaterials, interfacial engineering, and sustainable energy technologies.