Developing visible-light-active photocatalysts with well-aligned band edges and interface-driven carrier separation is essential for suppressing carrier recombination and accelerating redox kinetics. Despite having a moderate band gap and abundant amine-rich sites, bulk g-C3N4 often shows limited photocatalytic efficiency due to suboptimal band alignment and poor electronic conductivity. Here, we developed size-controlled plasmonic systems by integrating silver quantum dots (AgQDs) or nanoparticles (AgNPs) with exfoliated g-C3N4 (eCN) to boost light absorption and interfacial charge separation. Spatially confined metallic species modulate the local electronic environment of eCN, forming a Schottky junction that controls directional electron transfer from eCN to AgQDs. The AgQDs serve as effective electron sinks, thereby suppressing carrier recombination and boosting overall catalytic efficiency. The modified band edges promote the generation of both superoxide (•O2–) and hydroxyl radicals (•OH). AgQD3@eCN exhibited an impressive H2 evolution (15.2 mmol·g–1·h–1) and methylene blue (MB) degradation (rate constant 0.036 min–1), surpassing the corresponding performance metrics of AgNPs-anchored eCN (AgNP3@eCN). Density functional theory (DFT) calculations reveal an electronic band gap reduction from 3.2 eV for eCN to 2.7 eV after AgQD decoration, confirming the experimental band gap narrowing of AgQD3@eCN. The H2 adsorption energy (−0.74 eV) demonstrates that Ag-anchored eCN offers thermodynamically favorable active sites for photocatalytic H2 evolution. This study highlights a nanoscale confinement strategy that simultaneously tunes the band structure and activates surface sites, thereby enabling superior photocatalytic performance.
Pramanik et al. (Wed,) studied this question.