Abstract: A photoelectrosynthetically active heterostructure (PAH) is manufactured by forming or providing cavities in an electrically insulating material; forming or providing an electrically conductive layer on a side of the electrically insulating material; depositing an electrocatalyst cathode layer in the cavities; depositing one or more layers of light-absorbing semiconductor material in the cavities; depositing an electrocatalyst anode layer in the cavities; removing the layer of electrically conductive metal; and forming a hydrogen permeable layer over the electrocatalyst cathode layer. The one or more layers of light-absorbing semiconductor material can form a p-n junction or Schottky junction. The PAH can be used in photoelectrosynthetic processes to produce desired products, such as reduction product (e.g., methane gas, methanol, or carbon monoxide) from carbon dioxide and liquid waste streams.