The theoretical construction of two-dimensional materials to generate the van der Waals heterostructures (vdWHs) has recently been impersonated as a fascinating means for designing novel nano-electronic and optoelectronic devices. In this contribution, first principles calculations by PBE and hybrid HSE06 functional are performed to explore the electronic properties and photocatalytic performances of ZnO/graphene-like (g-GeC) vdWHs. Our results indicate that the ZnO/g-GeC vdWH owns a type-II band alignment and a direct band gap of 2.734 eV under HSE06. The reduction/oxidation potentials of H2O, and CO2 (transited into CO, HCHO, and CH4 molecules) are all respectively within the CBM/VBM of ZnO/g-GeC vdWH, demonstrating its significant potential for photocatalytic applications. Additionally, the efficient hindrance for photogenerated electron–hole pair recombination can be expected due to the built-in electric field (Eint) caused by the charge transfer at the interface region. Enhanced optical absorption in the visible light region is also presented for the ZnO/g-GeC vdWH compared with its two components, as well as the two other vdWH photocatalysts. Further, the modulated photocatalytic properties under varied pH conditions imply that an acid condition is more favorable to the water splitting process. The linear-like evolution trend of the band gap for the ZnO/g-GeC vdWH under a vertical strain predicts it as a potential candidate for nano pressure sensors. These findings together direct a forward strategy for designing excellent nano-electronic and optoelectronic devices based on the ZnO/g-GeC vdWH nanocomposite, particularly for a photocatalyst, predicting its numerous prospective applications in the field of hydrogen production and the atmosphere protection.