Laser‐Ablated Cu ₂ O Inks Enable Stable, Flexible Spray‐Processed Photocathodes

Cu 2 O is a benchmark photocathode for solar‐driven hydrogen production, but its application is limited by poor interfacial stability and reliance on complex protective multilayers. Here, we combine pulsed laser ablation in liquid (LAL) with ultrasonic spray coating to produce fully solution‐processed Cu 2 O inks that can be deposited as thin, uniform films. LAL yields compact nanogranular layers embedding a controlled fraction of Cu 0 nanodomains, enhancing interfacial conductivity while preserving the Cu 2 O crystalline framework. Under near‐neutral conditions and mild, nondestructive bias (+0.2 V vs reversible hydrogen electrode), LAL‐based photocathodes exhibit reduced charge–transfer resistance, faster HER interfacial kinetics, and stable photocurrent retention. In contrast, microwave‐derived Cu 2 O films suffer from poor cohesion and rapid electrochemical and structural degradation. Correlative electrochemical and post‐mortem analyses demonstrate that LAL produces defect‐tolerant Cu 2 O/Cu 0 interfaces capable of sustaining device functionality in conditions where unprotected Cu 2 O typically fails. These results position laser‐ablated Cu 2 O inks as a platform for spray‐deposited and flexible photoelectrochemical architectures without complex protective stacks.