Over a decade, a significant advancement in the development of nanohybrids has been observed to address the challenges related to sustainable energy systems. In this regard, the review critically examines the emerging functions of carbon-based quantum dots (CQDs) and graphene-based quantum dots (GQDs) and their nanohybrids in photoelectrochemical (PEC) applications, focusing on their different physicochemical properties. Nanohybrids constituting CQDs and GQDs can be breakthrough materials, which have evolved as emerging materials recently in PEC research owing to the mirrored properties of conventional quantum dots. Moreover, the surface chemistry and the electronic structure governed by the size of the quantum dots (QDs) facilitate wide tailoring opportunities in the nanohybrids, serving multifunctionality. A perspective on material design and probability is put forward. Understanding their individual contributions prior to exploring their impact on the PEC system is highly essential. The successful creation and functionality of CQDs/GQDs nanohybrids depend on the composite/nanohybrid processing of CQDs/GQDs while maintaining their intrinsic properties in the nanohybrid forms. The application of CQDs/GQDs in PEC applications remains largely experimental and lab-scale at this stage. Establishing a detailed structure-performance-stability relationship is crucial while conducting permutation-combination of different PEC experiments, integrating physicochemical characterization's, and understanding the QDs properties.