Wavelength-Tailoring Copper Oxidation States for Tunable Photoelectrochemical Syngas Generation

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Photoelectrochemical CO2 reduction (PEC CO2RR) to syngas is crucial for green chemistry.
• Controlling the CO/H2 ratio in syngas is a significant challenge.
• Existing methods using thin-film semiconductor photocathodes have fabrication limitations and struggle to tune the CO/H2 ratio.

Purpose of the Study:

• To develop a simple photodeposition method for fabricating a photoelectrocatalyst for tunable PEC CO2RR.
• To precisely control the CO/H2 ratio by regulating the electronic structure of active sites.
• To overcome the limitations of traditional fabrication methods for PEC CO2RR.

Main Methods:

• A simple photodeposition method was employed to load Cu2-xTe onto 1% S-doped ZnTe/ZnO.
• The oxidation state of copper (+1 to +2) was precisely controlled by varying the deposition light wavelength (violet to red).
• The electronic structure and catalytic properties were investigated in relation to copper oxidation state and deposition wavelength.

Main Results:

• The photodeposition method allowed tunable regulation of the Cu oxidation state by controlling light wavelength.
• Shorter wavelengths led to reduced Cu valence, shifting the d-band center and increasing electron density at active sites.
• Cu@S-ZnTe/ZnO exhibited a tunable CO/H2 molar ratio from 0.45 to 1.70.
• CO selectivity was enhanced with suppressed hydrogen evolution.

Conclusions:

• The proposed photodeposition method offers a simple and effective way to fabricate photoelectrocatalysts for PEC CO2RR.
• Precise control over the CO/H2 ratio is achievable by tuning the copper oxidation state via deposition light wavelength.
• The developed photoelectrocatalyst shows significant potential for practical applications in green chemical production.