Efficiency of splitting water with semiconducting photoelectrodes

• Published in: Journal of the Electrochemical Society Vol. 131; no. 6; pp. 1258 - 1265
• Main Authors: WEBER, M. F, DIGNAM, M. J
• Format: Journal Article
• Language: English
• Published: Pennington, NJ Electrochemical Society 01.06.1984
• Subjects: Applied sciences; Energy; Exact sciences and technology; Natural energy; Solar energy; Canada; Maximum; Hydrogen; Energy conversion; Solar energy; Production; Photoelectrolytic cell; Yield; Energy storage
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.2115797

Solar-conversion efficiencies for splitting water with semiconducting photoelectrodes are calculated from basic thermodynamic principles combined with transport properties matching those of the best materials presently available. Assuming no further constraints, upper-limit estimates of efficiencies achievable via semiconductor photoelectrochemical cells (PECs) operating with no external electrical bias are derived. Both one-photon and two-photon configurations are considered. A one-photon PEC is found to have an upper-limit efficiency of about 7 percent (AM-1.2 solar energy to chemical potential energy stored as H2). For two-photon configurations, the upper limit for a p-n PEC is about 10 percent, while for a tandem PEC it is about 18 percent. The tandem cell configuration is the least sensitive to the choice of materials parameters and transport losses and yields the highest efficiencies. Significant increases in conversion efficiencies result from assuming lower oxygen overpotentials and higher photoelectrode fill factors than have been achieved so far, the latter being the more important.