Solar Water Splitting: Beating the Efficiency of PV-Electrolysis with Tandem Cell Photoelectrolysis

摘要

Solar water splitting is a promising route for hydrogen production from renewable sources: water and sunlight. This can be readily achieved by combining two commercial technologies: photovoltaics (PV) and electrolysis. Such combinations have been demonstrated and tested in self-sufficient solar houses, solar hydrogen refueling stations, and PV solar power plants. Unfortunately, PV-powered electrolysis (PV-electrolysis for short) is too expensive for large-scale solar hydrogen production. This motivates research on photoelectrochemical (PEC) cells that split water by photoelectrolysis, thereby combining the functions of light harvesting and electrolysis together. Such PEC cells can be combined in tandem with PV cells to construct a hybrid system that co-generates electrical power and hydrogen fuel. This work compares the efficiency of PV-PEC tandem cells and PV-electrolysis systems. It shows (see figure below) that in order to beat PV-electrolysis, PEC water splitting cells should produce sufficient photovoltage so that they could be operated at a bias smaller than 1 V (provided by the PV cell).