From Type‑I to S‑Scheme: Coordination-bridged CuInS₂-CdS heterojunction for enhanced photocathodic protection

Coordination CIS-EDTA-CdS S-scheme heterojunction for PEC cathodic protection. • EDTA: bifunctional layer, passivating defects and modulating band positions. • S-scheme charge transfer enhances carrier separation and suppresses recombination. The development of photoanodes combining broad-spectrum light response with efficient charge separation is crucial for photoelectrochemical cathodic protection. In this work, an atomic-scale S-scheme heterojunction was constructed between narrow-bandgap CuInS₂ (CIS) and CdS via coordination-bond interface engineering. Specifically, EDTA was first employed as a small-molecule bridging agent to passivate dangling bonds and surface defects on CIS through coordination interactions. Subsequently, CdS was grown in situ onto the CIS-EDTA surface, yielding the CIS-EDTA-CdS composite photoanode. Results demonstrate that EDTA modification not only suppresses non-radiative recombination but also directionally tailors the band structure of CIS, transforming the heterojunction from a Type-I to an S-scheme configuration. The optimized composite photoanode achieves a photocurrent density of 1.3 mA·cm⁻² under light and shifts the corrosion potential of the coupled 304 stainless steel to −1.15 V (vs. NHE). Mechanistic investigations reveal that the S-scheme charge-transfer pathway promotes the recombination of conduction-band electrons from CdS with valence-band holes from CIS-EDTA, while preserving the high-energy electrons on the CIS-EDTA side for effective cathodic protection. This study provides a new paradigm for the application of atomic-scale interface engineering in photoelectrochemical anticorrosion, highlighting the potential of coordination-bridge strategies in designing high-performance photoanodes. Coordination-bonding engineered CuInS₂-EDTA-CdS heterojunction for boosted photocathodic protection Download: Download high-res image (337KB) Download: Download full-size image