Intercepting carrier–defect trapping via ultrafast electron extraction across carbon interface to boost photocatalytic H2 evolution

Tailoring defect states to achieve prolonged charge separation lifetimes is essential for improving photocatalytic hydrogen evolution. However, the role of defects, whether as recombination centers or electron traps, remains controversial. Here, we construct a Schottky type CdIn 2 S 4 -NC/MoSe 2 (CISNCM) ternary heterojunction, where hollow nitrogen doped carbon (NC) serves as an electron super bridge that simultaneously forms two Schottky interfaces. A combination of XPS, Mott–Schottky, and Bader charge analysis (CdIn 2 S 4 : −2.65 e; MoSe 2 : −0.13 e; NC: +2.78 e) demonstrates directed electron flow toward NC. Femtosecond transient absorption spectroscopy unveils that photogenerated electrons are sequentially captured by shallow sulfur vacancies (τ 1 ≈ 13.4 ps), deep defects (τ 2 ≈ 198.4 ps), and finally undergo free electron radiative recombination (τ 3 ≈ 2055.5 ps) in pristine CdIn 2 S 4 with deep level non radiative recombination dominating the loss channel. Upon forming the CdIn 2 S 4 -NC/MoSe 2 composite with the best hydrogen evolution performance (21%CISNCM) heterojunction, an ultrafast interfacial electron transfer (τ 1 ≈ 0.3 ps) emerges that kinetically outcompetes both shallow and deep trapping, slashing the deep level recombination amplitude from −1.14 to −0.309. This kinetic override unveils a previously masked deep level bound electron recombination pathway (τ 4 ≈ 1414.3 ps) and boosts the photocatalytic H 2 evolution rate to 17306.5 μmol·g −1 ·h −1 — 25.3 fold that of pristine CdIn 2 S 4 with well stability. Our work demonstrates that NC-interface ultrafast electron transfer kinetically suppresses detrimental deep defects, rendering them inconsequential and providing guidance for designing high-efficiency sulfide photocatalysts in terms of photocarrier dynamics.