Alkali Cation Engineered Chemical Self‐Oxidation of Copper Oxide Nanowire‐Based Photocathodes. Issue 3 (28th December 2022)

• Record Type: Journal Article
• Authors: Su Kim, Dong; Hoon Choi, Ji; Deshpande, Nishad G.; Hyeon Lee, Hak; Woong Lee, Kun; Young Oh, Shin; Koun Cho, Hyung
• Is Part Of: ChemSusChem. Volume 16:Issue 3(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-28
• Subjects: nanowires -- oxidation -- hydrogen -- photoelectrochemistry -- water splitting; Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.202202074
• Languages: English
• ISSNs: 1864-5631

Abstract

Abstract: Hydrogen energy production through photoelectrochemical (PEC) water splitting has great potential in the field of renewable energy. This study focuses on the hydration enthalpy difference of cations (Li +, Na +, and K + ) in an aqueous solution for the chemical self‐oxidation process without an external applied bias. The thickness of the cation/H2 O double layer is controlled. The starting materials are low‐cost copper foil and the synthesis uses alkali cation‐engineered chemical self‐oxidation. Li + ions are strongly attracted to water molecules. This forms a sufficient OH − layer on the Cu foil surface. By accelerating the oxidation reaction, a large surface area of Cu(OH) x nanowires (NWs) with high purity and a uniform shape are obtained. This optimal p‐type Cu2 O NWs photocathode is CuO‐free, has the highest conductivity, and is fabricated through phase transition using precise vacuum annealing. The other alkali cations produce the Cu2 O/CuO mixed or CuO phases that degrade the PEC performances with severe corrosive reactions. The Cu/Li : Cu2 O/AZO/TiO2 /Pt photocathode has a 50 h stability with a photocurrent density of 8.4 mA cm −2 at 0 VRHE . The fabricated photoelectrode did not structurally collapse after stability measurements during this period. The captured hydrogen production was in agreement with the calculated faradaic efficiency. Abstract : Do it yourself : Hydration enthalpy difference of Li +, Na +, and K + in aqueous solution is used for chemical self‐oxidation without an external applied bias. The thickness of the cation/H2 O double layer is controlled. Li + ions are strongly attracted to H2 O. This forms a sufficient OH − layer on the substrate. By accelerating the oxidation reaction, a CuO‐free Cu2 O nanowire photocathode is obtained.