Herein, we have synthesized zinc oxide (ZnO) particles from the zinc ash generated as waste in the galvanization process in the steel industry, ZnO particles were decorated with copper oxide (CuO) nanoparticles, and then further activated by reducing them to get a heterojunction photocatalyst (ZCu@ZnO). Thereafter, ZCu@ZnO is utilized for the photoreduction of carbonate to acetic acid (AcOH) in a H2O2-water mixture as a hydrogen-rich solvent under the illumination of various light sources. Moreover, various physical and chemical parameters, such as solvent mixture, light sources (monochromatic lights and sunlight), photocatalysts, time, etc., were also optimized to get the maximum yield of AcOH (∼0.47 M). The mechanism of photoreduction of carbonate to AcOH is also being proposed based on scavenging experiments of free radicals.