The research plan aims to improve solar to hydrogen conversion efficiency by integrating Si photovoltaic semiconductors and novel electrolytic catalyst electrodes in a single electrolysis cell. The conversion of solar energy into electricity by solar cell plays an important role in renewable energy development. However, the storage of the generated electricity remains a challenging problem. The conversion of electric energy into hydrogen provides a potential solution. Although a direct connection of solar cell to an electrolysis cell is straightforward. The electric current transmission will cause energy loss. By integrating photovoltaic semiconductor with electrolysis catalyst together, it can avoid the transmission loss. In addition, the generated carriers can be quickly used by catalyst for water splitting, therefore improving overall solar to hydrogen energy conversion efficiency. A typical design is to directly plate the anode catalyst material on the surface of the photovoltaic semiconductor. Catalyst electrodes play an important role here. In addition to catalyze water splitting reaction, it can also change the band bending of semiconductor, thereby affecting the photo voltage and current generation, which is very important for driving water redox reaction. Subproject one will study structured catalyst on semiconductor surface to improve the photo voltage and current generation from photoanode, thereby improving the solar to electricity conversion efficiency. Subproject two will study modified graphene catalyst to replace the precious catalyst metals, thereby reducing the material cost. The research results of two subprojects on anode and cathode will be integrated together. The goal is to demonstrate a >15% solar to hydrogen energy conversion efficiency electrolysis cell.