The use of light as a catalytic prompt for the synthesis of industrial relevantcompounds is widely explored in the past years, with a special considerationover the hydrogen evolution reaction (HER). However, semiconductors forheterogeneous photocatalysis suffer from fast charge recombination and,consequently, low solar-to-hydrogen efficiency. These drawbacks can bemitigated by coupling photocatalysts with an external circuit that canphysically separate the photogenerated charge carriers (electrons and holes).For this reason, photoelectrochemical (PEC) production of hydrogen is underthe spotlight as promising green and sustainable technique and widelyinvestigated in numerous publications. However, considering that asignificant fraction of the hydrogen produced is used for reduction processes,the development of PEC devices for direct in situ hydrogenation can addressthe challenges associated with hydrogen storage and distribution. ThisPerspective aims at highlighting the fundamental aspects of HER from PECsystems, and how these can be harnessed toward the implementation ofsuitable settings for the hydrogenation of organic compounds of industrialvalue.
