Cu2O/CuO Bilayered Composite as a High-Efficiency Photocathode for Photoelectrochemical Hydrogen Evolution Reaction

Yang Yang,Peng Diao,Qingyong Wu,Di Xu

doi:10.1038/srep35158

Yang Yang, Peng Diao + Show 2 more

Open Access

https://doi.org/10.1038/srep35158

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Journal: Scientific Reports	Publication Date: Oct 17, 2016
Citations: 385	License type: CC BY 4.0

Affiliation: Beihang University

Abstract

Solar powered hydrogen evolution reaction (HER) is one of the key reactions in solar-to-chemical energy conversion. It is desirable to develop photocathodic materials that exhibit high activity toward photoelectrochemical (PEC) HER at more positive potentials because a higher potential means a lower overpotential for HER. In this work, the Cu2O/CuO bilayered composites were prepared by a facile method that involved an electrodeposition and a subsequent thermal oxidation. The resulting Cu2O/CuO bilayered composites exhibited a surprisingly high activity and good stability toward PEC HER, expecially at high potentials in alkaline solution. The photocurrent density for HER was 3.15 mA·cm−2 at the potential of 0.40 V vs. RHE, which was one of the two highest reported at the same potential on copper-oxide-based photocathode. The high photoactivity of the bilayered composite was ascribed to the following three advantages of the Cu2O/CuO heterojunction: (1) the broadened light absorption band that made more efficient use of solar energy, (2) the large space-charge-region potential that enabled a high efficiency for electron-hole separation, and (3) the high majority carrier density that ensured a faster charge transportation rate. This work reveals the potential of the Cu2O/CuO bilayered composite as a promising photocathodic material for solar water splitting.

Highlights

Cu2O and CuO have a direct bandgap of approximately 2.0–2.5 eV28–30,32,39,53–60 and 1.3–1.7 eV31,36,37,60–62, respectively, depending on the preparation methods and conditions
(2) Cu2O and CuO are more stable at a higher potential for PEC hydrogen evolution reaction (HER) because a high potential restrains the photoreduction of Cu2O to metal copper, which was believed to be the main cause of the low stability of copper oxides during PEC HER28,31
We report a facile method that involved a repeated double-potential pulse chronoamperometric (r-DPPC) deposition and a subsequent thermal oxidation to prepare the Cu2O/CuO composite photocathodes

Summary

Introduction

Cu2O and CuO have a direct bandgap of approximately 2.0–2.5 eV28–30,32,39,53–60 and 1.3–1.7 eV31,36,37,60–62, respectively, depending on the preparation methods and conditions. The high electron-hole recombination rate in Cu2O and CuO prevent these two materials from being highly efficient photocathodes for HER To address this issue, one strategy is to construct heterojunction structures with other semiconductors[5], such as CuO/ZnO63,64, CuO/TiO265, and Cu2O/TiO266, for efficient separation of photogenerated electron-hole pairs. The Cu2O/CuO heterojunction facilitates electron-hole separation and can improve photo-to-chemical energy conversion efficiency[41,42,47,48,49,50,51,67,68] It is desirable for a photocathodic material, especially copper-oxide-based materials, to be highly active at more positive potential region (>0.40 V vs RHE) because of the following two reasons. This work shows the potential of the Cu2O/CuO bilayered composite as a photocathodic material for efficient HER, and provides an ease, low-cost, and scalable strategy to prepare the

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