Three-Dimensional Cu-Based Nanostructures for Photoelectrochemical Water Splitting and Electrochemical Carbon Dioxide Reduction

• Published in: ACS applied energy materials Vol. 7; no. 15; pp. 6569 - 6577
• Main Authors: Dong, Wan Jae, Lim, Kwan Woo, Cho, Hyung Won, Yoo, Chul Jong, Ham, Juyoung, Cho, Won Seok, Park, Jae Yong, Lee, Jong-Lam
• Format: Journal Article
• Language: English
• Published: American Chemical Society 12.08.2024
• Subjects: copper oxide; nanostructure; water splitting; carbon dioxide reduction; Cu−Sn
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.4c01197

Photoelectrochemical (PEC) water splitting and electrochemical carbon dioxide (CO2) reduction have emerged as viable methods for future solar-to-chemical conversion. Among various candidates, copper oxide (CuO) stands out as a promising photocathode material due to its suitable optical band gap, favorable band alignment, and low cost. Here, we report a low-temperature solution process to fabricate CuO branched nanowires (b-NWs) to explore the effect of surface morphology on the activity of PEC water splitting. CuO b-NWs provide a larger surface area, homogeneous surface crystallinity, and higher light absorption in near-surface regions than the conventional CuO NWs. As a result, CuO b-NWs serve as an efficient photocathode for PEC water splitting, exhibiting an approximately 2.6 times improved photocurrent density. Moreover, CuO b-NWs could be electrochemically reduced to Cu b-NWs, and then Sn nanoparticles are coated to form Cu–Sn b-NWs for electrochemical CO2 reduction. As the geometric structure became more complex in the order of Cu–Sn film, NWs, and b-NWs, carbon monoxide (CO) selectivity and production rate increase. The optimized Cu–Sn b-NWs result in the highest CO faradaic efficiency of 99.8% at −0.8 VRHE. This study demonstrates that the rational design of three-dimensional nanostructures can enhance the optical properties of a photoelectrode and improve the electrochemical performance.