Low-defect Cu2O films with vertical grains via tartaric acid assisted solution growth for efficient photoelectrochemical water splitting

doi:10.1016/S1872-2067(26)65202-3

Abstract

Abstract:

Cu₂O is among the most promising metal oxide semiconductors for solar water splitting, yet its performance is often limited by structural defects and poor charge transport. Here, we report a tartaric acid-assisted solution growth strategy to fabricate high-quality Cu₂O films (T-Cu₂O) with reduced defect density, prolonged carrier lifetimes, and enhanced electrical conductivity. Microstructural analysis reveals that T-Cu₂O films consist of vertically aligned columnar grains exceeding 1 μm in length, spanning the entire film thickness. This contrasts with the disordered grains formed in conventional lactic acid-assisted films (L-Cu₂O), which impede charge transport. Upon integration with overlayers and RuO_x cocatalysts, the T-Cu₂O photocathode delivers a photocurrent density of 8.0 mA cm^-2 at 0 V vs. RHE—23% higher than its L-Cu₂O counterpart. Surface photovoltage measurements further confirm significantly improved charge separation in T-Cu₂O. This work establishes a facile solution-based strategy for producing high-quality Cu₂O photoelectrodes with enhanced efficiency for photoelectrochemical water splitting.

Key words: Photoelectrochemical water splitting, Photoelectrode, Cu₂O, Electrodeposition, Tartaric acid

Linxiao Wu, Yumeng Han, Jinshui Cheng, Yushuai Sang, Xiang Chen, Yaqing Zhang, Xuewen Fu, Jingshan Luo. Low-defect Cu₂O films with vertical grains via tartaric acid assisted solution growth for efficient photoelectrochemical water splitting[J]. Chinese Journal of Catalysis, 2026, 90: 243-252.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(26)65202-3

https://www.cjcatal.com/EN/Y2026/V90/I11/243

Figures/Tables 5

Fig. 1. (a) XRD patterns of T-Cu2O electrodeposited from a tartrate stabilized copper sulfate solution and L-Cu2O film from a lactate-stabilized copper sulfate solution. Indexes were taken from the following patterns: Au PDF#99-0056, Cu2O PDF#05-0667, FTO PDF#41-1445. XPS spectra Cu 2p (b) and XPS O 1s spectra (c) of T-Cu2O film and L-Cu2O film. Top-view SEM images of T-Cu2O films with electrodeposition time of 1 min (d), 5 min (e), and 50 min (f). Top-view SEM images of L-Cu2O films with electrodeposition time of 1 min (g), 5 min (h), and 100 min (i).

Fig. 2. Cross-sectional SEM image (a), EBSD pattern-quality map (b), and EBSD orientation-distribution map (c) perpendicular to substrate highlighted by false colors within the related inverse pole figure of T-Cu2O film (electrodeposition time for 50 min). Cross-sectional SEM image (d), EBSD pattern-quality map (e), and EBSD orientation-distribution maps (f) perpendicular to substrate of L-Cu2O film (electrodeposition time for 200 min). (g,h) Schematic diagram of charge transport in Cu2O films.

Fig. 3. Mott-Schottky plots (a) and PL spectra (b) of T-Cu2O and L-Cu2O films. Streak camera images of TRPL of T-Cu2O (c) and L-Cu2O (d) films. (e,f) Corresponding decay traces of the near band emission extracted from (c) and (d) fitted using a biexponential function. C-AFM current mapping images of T-Cu2O (g) and L-Cu2O (h) films. CPD of T-Cu2O (i) and L-Cu2O (j) films.

Fig. 4. (a) J-V curve of T-Cu2O and L-Cu2O photocathodes (Cu2O/Ga2O3/ZnGeOx/TiO2/RuOx) under continuous simulated one-sun AM 1.5 G (solid line) and dark condition (dashed line). (b) J-V curve of T-Cu2O and L-Cu2O photoelectrodes under chopped simulated AM 1.5G illumination. Statistical current density at 0 V vs. RHE (c) and onset potential (d) of Cu2O photoelectrodes under continuous simulated one-sun air mass 1.5 G condition. (e) IPCE spectra under monochromatic illumination of T-Cu2O and L-Cu2O photoelectrodes at 0 V vs. RHE. (f) Stability test of T-Cu2O photocathode at 0.5 V vs. RHE. All measurements were performed in a pH 5.0 electrolyte solution under constant stirring at 500 rpm.

Fig. 5. SPVM images of T-Cu2O (a) and L-Cu2O (b) photoelectrodes (Cu2O/Ga2O3/ZnGeOx/TiO2). SPVM images of T-Cu2O (d) and L-Cu2O (e) photoelectrodes with RuOx catalyst (Cu2O/Ga2O3/ZnGeOx/TiO2/RuOx). The vertical height gradient denotes film surface topography, and the color gradient represents CPD. SPV spectra for T-Cu2O and L-Cu2O photoelectrodes without (c) and with (f) catalyst. Charge transfer efficiency (ηtransfer) (g) and charge separation efficiency (ηsep) (h) of Cu2O photocathodes. (i) The open-circuit potential of Cu2O/Ga2O3/ZnGeOx/TiO2/RuOx photocathodes under chopped illumination condition in pH 5 electrolyte.

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Low-defect Cu₂O films with vertical grains via tartaric acid assisted solution growth for efficient photoelectrochemical water splitting

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