Photocorrosion of Hematite Photoanodes in Neutral and Alkaline Electrolytes

BENAVENTE LLORENTE, VICTORIA; JENEWEIN, KEN J.; BIERLING, MARKUS; KÖRNER, ANDREAS; HUTZLER, ANDREAS; KORMÁNYOS, ATTILA; CHEREVKO, SERHIY

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Año: 2023 vol. 127 p. 19687 - 19697

1932-7447

Photoelectrochemical (PEC) water splitting is a promising energyconversion technology based on the harvesting of sunlight to produce greenhydrogen. One of the major challenges hindering the development of PEC devicesis the stability of photoanodes since most semiconductors are susceptible to anodicdecomposition in aqueous solutions. While hematite (α-Fe2O3) has been regardedas one of the most stable metal oxides to drive the oxygen evolution reaction inalkaline media, its photostability in a broad pH range is poorly investigated. In thiswork, we study the dissolution of model Fe2O3 thin films in different electrolytes,including unbuffered and buffered neutral, near-neutral, and alkaline solutions,using on-line PEC inductively coupled plasma mass spectrometry. Fe leaching isobserved in all studied unbuffered electrolytes under irradiation while phosphate-buffered electrolytes reveal a dramatic stabilityenhancement at all pHs. The latter might imply that phosphate buffers either alleviate local acidification in the close vicinity of theelectrode−electrolyte interface during the reaction or that specific adsorption of phosphate anions at the α-Fe2O3 surface couldmitigate dissolution. Furthermore, we explore the long-term stability of α-Fe2O3 using a three-electrode bulk PEC cell. In the longrun, phosphate buffers do not represent an optimal electrolyte choice either, as the surface Fe oxide gradually converts to Fephosphates that are not photoelectrochemically active. Our work demonstrates that photocorrosion of Fe2O3 within electrolytes thatare commonly used in the literature is not negligible and should be considered for designing stable semiconductor interfaces.