Photoelectrochemical Solar Water Splitting—Investigating Degradation Mechanisms in Long-Term Practical Testing

The development of advanced water-splitting systems for low-cost hydrogen production has become a strategic priority in combating climate change as the U.S. Department of Energy (DOE) announced $750 million to support domestic hydrogen industry in March 2024.^[1] Photovoltaics coupled with electrolyzers, or photoelectrocatalytic water splitting, that are sustainable methods of harnessing renewable energy to produce hydrogen, have raised intense research and industrial attention. Nevertheless, the projected levelized cost of hydrogen (LCOH) from PV-EC integrated systems (3.86 $/kg_H2) or PEC systems (6.32 $/kg_H2) ^[2] is still not competitive with that of 1.06- 1.64$/kg_H2 from traditional steam methane reforming (SMR) and is far away from DOE set cost target of 1$/kg_H2 in 2031. ^[3-4]
We have developed a working set of device- and system-level performance metrics which can be used for comparison of lab-scale and larger demonstrations. While many reports in the literature have attractive solar to hydrogen (STH) efficiencies of 10%, none come within an order of magnitude of our projected lifetime metrics. This analysis shows that the durability of PC and PV-EC systems has become the primary obstacle in achieving the DOE's goal of producing hydrogen using renewable energy sources.
We performed baseline analysis of the durability of a PV-EC system constructed from commercially available (and scalable) components. The system is comprised of a silicon minimodule with illuminated area of 69.3 cm² coupled with a proton-exchange-membrane (PEM) electrolyzer with initial current of ~500 mA at 1.8 V and active area of 2.9 cm². Performance results from a 500-hour continuous outdoor test will be presented.
Initial work to access the main degradation mechanisms will also be presented: atomic force microscopy (AFM) to observe the evolution of electrode surface morphology and inductively coupled plasma mass spectrometry (ICP-MS) to detect component corrosion.
Finally, we will describe our efforts towards constructing a comprehensive database of experimental PEC and PV-EC water-splitting activity, along with environmental parameters of sunlight intensity and temperature, to accelerate development of durable devices.
[1] Biden-Harris Administration announces $750 million to support America’s growing hydrogen industry as part of investing in America Agenda. Department of Energy, March 13, 2024. https://www.energy.gov/articles/biden-harris-administration-announces-750-million-support-americas-growing-hydrogen.
[2] Cattry, Alexandre, Hannah Johnson, Despoina Chatzikiriakou, and Sophia Haussener. "Probabilistic Techno-Economic Assessment of Medium-Scale Photoelectrochemical Fuel Generation Plants." Energy & Fuels (2024).
[3] Chung, Doo Hyun, Edward J. Graham, Benjamin A. Paren, Landon Schofield, Yang Shao-Horn, and Dharik S. Mallapragada. "Design space for PEM electrolysis for cost-effective H₂ production using grid electricity." Industrial & Engineering Chemistry Research 63, no. 16 (2024): 7258-7270.
[4] Liu, Yaohua, David A. Cullen, Alexey Serov, Hanyu Wang, John Ankner, Leighton Coates, Mamontov Eugene, and Shuo Qian. Second Target Station Project: STS Cross-Directorate Workshop on Hydrogen Fuel. No. ORNL/TM-2024/3477. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States), 2024.

This work was supported by the HydroGEN Advanced Water Splitting Materials Consortium, established as part of the Energy Materials Network under the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office.