A system and method employing sunlight energy for the reduction of carbon dioxide into methane and water are disclosed. Methane gas may then be stored for later use as fuel. The system and method may use inorganic capping agents that cap the surface of semiconductor nanocrystals to form photocatalytic capped colloidal nanocrystals, which may be deposited on a substrate and treated to form a photoactive material. The photoactive material may be employed in the system to harvest sunlight and produce energy necessary for carbon dioxide reduction. The system may also include elements necessary to collect and transfer methane, for subsequent transformation into electrical energy.