Atomically tunable photo-assisted electrochemical oxidation process design for the decoration of ultimate-thin CuO on Cu2O photocathodes and their enhanced photoelectrochemical performances. Issue 41 (15th October 2020)

• Record Type: Journal Article
• Authors: Kim, Dong Su; Kim, Young Been; Jung, Sung Hyeon; Deshpande, Nishad G.; Choi, Ji Hoon; Lee, Ho Seong; Cho, Hyung Koun
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 41(2020)
• Page Start: 21744
• Page End: 21755
• Publication Date: 2020-10-15
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0ta06010k
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : A representative method of forming CuO thin films on Cu2 O photoabsorbers is simple annealing oxidation at high temperature in a controlled oxygen atmosphere, but the typical oxidation process is irregular, resulting in a high density of defect sites. Abstract : A representative method of forming CuO thin films on Cu2 O photoabsorbers is simple annealing oxidation at high temperature in a controlled oxygen atmosphere, but the typical oxidation process is very quick and irregular, resulting in a high density of defect sites. To maximize the beneficial effect of CuO/Cu2 O heterojunction photocathodes, novel criteria for CuO preparation have been suggested: (1) in-plane epitaxy with Cu2 O, (2) atomic layer-by-layer growth, (3) ultimate-thin and completely conformal coating, and (4) minimized internal defects. As a novel strategy to achieve these criteria, we propose a photo-assisted electrochemical oxidation (PAEO) method, where the Cu2 O surface is precisely phase-changed into the ultimate-thin CuO layer with a thickness of 4 nm via fine thickness control using photoenergy and an external potential at room temperature. The produced CuO crystals are grown on Cu2 O without generating structural defects by accommodating the epitaxial relationship below the critical thickness. From static and dynamic (photo)electrochemical analyses, the decoration of ultimate-thin CuO offers high electrical conductivity and fast charge transport, guarantees sufficient open-circuit potential (OCP), and substantially retains the initial OCP value by minimizing the contribution of recombination loss. Finally, the PAEO-treated photocathodes exhibit an excellent photocurrent density of 15 mA cm −2 (approaching the theoretical maximum current) and 8.3 mA cm −2 at 0 V vs. RHE in electrolytes with and without scavenger hydrogen peroxide (H2 O2 ), respectively, as well as a OCP of 0.78 V, even with the use of suboptimal Al-doped ZnO buffer layers.