Research Article pubs.acs.org/journal/ascecg
Direct Growth of Flexible and Scalable Photocathodes from α‑Brass Substrates Sriya Banerjee,† Yoon Myung,† Sankar Raman,§ and Parag Banerjee*,†,‡ †
Department of Mechanical Engineering & Materials Science, ‡Institute of Materials Science & Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, United States § Physical Electronics, Chanhassen, Minnesota 55317, United States S Supporting Information *
ABSTRACT: A facile, low cost method to grow robust and adherent, single phase metal oxides from an earth-abundant binary alloy has been outlined and its effectiveness as a photocathode for solar energy harvesting demonstrated. Cu0.7Zn0.3 (α-brass) foils were thermally dezincified (removal of surface Zn) at 450 °C and subsequently oxidized, by varying the temperature from 300 to 600 °C. The brass foil served as the oxide growth substrate as well as a conductive electrical contact for subsequent photoelectrochemical testing. CuO nanowires were seen for the 400 and 500 °C samples. ZnO phase was detected within the concave pores on the sample surface. The highest photocurrent of 1.8 mA/cm2 at −0.5 V vs Ag/ AgCl occurred for the sample oxidized at 500 °C with an incidentphoton-to-current-efficiency (IPCE) of 6.9% at 450 nm. This sample corresponds to the oxide with the lowest surface zinc content (10 at. %, measured by X-ray photoelectron spectroscopy), indicating that the presence of ZnO hinders the performance of the photocathode. The approach demonstrated in this work opens up possibilities for making large area, scalable photoelectrodes directly on conductive alloy substrates, leading to simpler electrode fabrication and opportunities for alloy recycling for sustainable energy harvesting. KEYWORDS: Copper oxide, Recyclable, Photocathode, Thermal oxidation, Brass, Alloy
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is usually limited by oxide flaking15,16 due to the volume expansion associated with the metal to metal oxide conversion. This is given by the Pilling−Bedworth (P-B) ratio17 as the volume of oxide produced to the volume of metal consumed in the process. For a P-B ratio >1, the oxide film forms cracks and peels off from the metal substrate, whereas for a P-B ratio
