Investigation of CO₂-to-CO Conversion by Cocatalyst-Free Epitaxial ZnTe Photocathodes

Year: 2026 DOI: 10.1021/acsaem.5c03133
In this study, we explore cocatalyst-free, single-crystalline, and epitaxial thin film zinc telluride (ZnTe) as a photocathode for CO₂-to-CO conversion. The study systematically examines the impact of electronic properties and crystal orientation using nitrogen-doped, p-type ZnTe (ZnTe:N) photocathodes grown on GaAs substrates by molecular beam epitaxy (MBE). Heavily doped ZnTe:N ([p] ≅ 10²⁰ cm–3) with a (100) orientation achieves a selective CO₂-to-CO Faradaic efficiency of 62% over a 200-mV potential window (with current densities of ∼0.1 mA·cm–2) without additional surface modifications. ZnTe:N of (100), (110), and (111) crystal orientations demonstrate different photoactivity, with the (100) and (110) orientations exhibiting three times higher photocurrent density compared to the (111) orientation despite their similar electronic properties. Overall, this study provides a foundation for further development of ZnTe-based tandem devices for photoelectrochemical CO₂ reduction.