A lack of uniformity in gauging the efficiency of different photoelectrochemical (PEC) water-splitting routes for sustainable hydrogen production stems for the absence of standardized measurement methods. A new best-practices guide prepared by an international team of researchers is intended to provide confidence in comparing results obtained at different sites and by different groups.

The guide explained in Frontiers in Energy Research offers a road map for the PEC community as researchers continue to refine the hydrogen evolution technology. These best practices were verified by U.S. Lawrence Berkeley National Laboratory and U.S. National Renewable Energy Laboratory via round-robin testing using the same testing hardware, PEC photoelectrodes and measurement procedures. Research into photovoltaics has allowed a certification of cell efficiencies, but PEC water-splitting efficiency measurements do not yet have a widely accepted protocol.

The new guide outlines a path so that all laboratories can follow a uniformity of experimental practices, beginning with the materials needed for the fabrication of photoelectrodes. Fabrication procedures, experimental setup and the process to measure the solar-to-hydrogen efficiency are also defined for the accurate and standardized direct measurement of the amount of hydrogen generated and process efficiency.

The U.S. Department of Energy’s Hydrogen and Fuel Cell Technologies Office has set 25% as the ultimate target for solar-to-hydrogen efficiency through PEC water-splitting, although preliminary cost analysis suggests that competitively costed hydrogen could be achieved with lower efficiencies. Photoelectrodes have demonstrated efficiencies from 10% to 20%.

Researchers from Technische Universität München (Germany) and Southern University of Science and Technology (China) also participated in the development of these best practices and guidelines.