“…[ 8 , 9 , 10 , 11 , 12 ] Their attractiveness relies on their superb optoelectronic properties, their compatibility with solution‐based manufacturing techniques, their ready‐to‐market photovoltaic performance, and their well‐positioned energy bands to trigger the hydrogen evolution reaction (HER), among others. [ 13 , 14 , 15 ] While typical chalcopyrite photocathodes utilize a complex buried junction architecture,[ 15 , 16 ] recently, a direct chalcopyrite/electrolyte interface has shown hours‐stable H 2 ‐related saturation photocurrents close to the theoretical limit based on their band gap. [ 13 , 14 ] While promising, given the multi‐atomic surface of chalcopyrites, the origin of the surface reactivity remains to be elucidated, and moreover, an explanation for the inferior turn‐on voltages ( V on ) exhibited by these bare chalcopyrites is still missing.…”