H ₂ O ₂ ‐Driven In Situ Etching and Ultrasonic Spray Pyrolysis Construct CdIn ₂ S ₄ /In(OH) ₃ Heterojunctions for Exceptional Photocatalytic Hydrogen Evolution

CdIn 2 S 4 /In(OH) 3 heterojunctions were constructed via a scalable ultrasonic spray pyrolysis method combined with H 2 O 2 ‐enabled in situ etching, in order to address the issues of photocorrosion, scarce active sites, and rapid charge recombination observed in pristine CdIn 2 S 4 . The optimized heterojunction, achieved using 50 µL of H 2 O 2 , demonstrates a significantly enhanced H 2 evolution rate of 736 µmol g −1 h −1 , which is 12 times greater than that of pristine CdIn 2 S 4 , along with stable performance throughout three consecutive catalytic cycles. Structural and chemical analyses verify the formation of a closely integrated heterojunction interface, which facilitates improved charge separation and efficient electron transfer from CdIn 2 S 4 to In(OH) 3 , as further corroborated by electrochemical and photoluminescence studies. A possible mechanism for hydrogen evolution is also proposed.