Cu₇S₄/M_xS_y (M=Cd, Ni, and Mn) Janus Atomic Junctions for Plasmonic Energy Upconversion Boosted Multi‐Functional Photocatalysis

Abstract Rational design/synthesis of atomic‐level‐engineered Janus junctions for sunlight‐impelled high‐performance photocatalytic generation of clean fuels (e.g., H 2 O 2 and H 2 ) and valuable chemicals are of great significance. Especially, it is appealing but challenging to acquire accurately‐engineered Janus atomic junctions (JAJs) for simultaneously realizing the plasmonic energy upconversion with near‐infrared (NIR) light and direct Z‐scheme charge transfer with visible light. Here, a range of new Cu 7 S 4 /M x S y (M=Cd, Ni, and Mn) JAJs are designed/synthesized via a cation‐exchange route using Cu 7 S 4 hexagonal nanodisks as templates. All Cu 7 S 4 /M x S y JAJs show apparently‐enhanced photocatalytic H 2 O 2 evolution compared to Cu 7 S 4 in pure water. Notably, optimized Cu 7 S 4 /CdS (CCS) JAJ exhibits the outstanding H 2 O 2 evolution rate (2.93 mmol g −1 h −1 ) in benzyl alcohol aqueous solution, due to the following factors: i) NIR light‐impelled plasmonic energy upconversion induced H 2 O 2 evolution, revealed by ultrafast transient absorption spectroscopy; ii) visible‐light‐driven direct Z‐scheme charge migration, confirmed by in situ X‐ray photoelectron spectroscopy. Besides, three different reaction pathways for H 2 O 2 evolution are disclosed by in situ electron spin resonance spectroscopy and quenching experiments. Finally, CCS JAJ also exhibits super‐high rates on H 2 and benzaldehyde co‐generation using visible‐NIR light or NIR light. This work highlights the significance of atomic‐scale interface engineering for solar‐to‐chemical conversion.