TY - JOUR A1 - Naumann, Kathrin A1 - Tichter, Tim A1 - Nielsen, Rasmus S. A1 - Seger, Brian A1 - Hansen, Ole A1 - Chorkendorff, Ib A1 - Vesborg, Peter C. K. T1 - Protection Materials on III–V Semiconductors for Photoelectrochemical CO Reduction N2 - Tantalum oxide (TaOx) and amorphous titanium dioxide (TiO2) are employed as protection materials for commercial GaInP/GaAs/Ge triple-junction solar cells to facilitate the unbiased photoelectrochemical reduction of carbon monoxide on nanostructured copper particles. It has been found that a photoelectrode protected by a 150 nm-thick layer of TiO2, capped with 8 nm TaOx, and decorated with copper nanocubes in the size of 150 nm can successfully drive the photoelectrochemical conversion of carbon monoxide to ethylene. Implemented into a photoelectrochemical flow reactor, which continuously supplies the active interface with CO-saturated electrolyte, the device achieves a faradaic efficiency of 24% under AM1.5G conditions. Direct attachment of the copper nanocubes to a protection layer of TiO2 in the absence of TaOx results in a strong hydrogen evolution reaction (HER) and no CO reduction products are found. This unexpected loss in selectivity is studied via post-operando X-ray photoemission spectroscopy and ion-scattering spectroscopy. No modifications in the redox state of TiO2 orsigns of H intercalation are found, while the preferential redeposition of small Cu nanoparticles is considered possible. This increasein HER appears specific for TiO2, as additional, purely electroanalytical experiments using tantalum oxide or carbon as a support layer for Cu nanocubes can produce ethylene effectively. KW - Photoelectrochemistry KW - Carbon Monoxide Reduction KW - Protection Material KW - Multi‐junction KW - Copper Catalyst PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618712 DO - https://doi.org/10.1021/acs.jpcc.4c04782 SP - 1 EP - 10 PB - American Chemical Society (ACS) AN - OPUS4-61871 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -