Strain engineering of dealloyed nanoporous cu for electrochemical CO(2) reduction
File(s)
Author(s)
Zhou, Yuxiang
Type
Thesis
Abstract
The electrochemical CO2 and CO reduction reaction (CO(2)RR) enables the recycling of greenhouse gases into valuable chemicals and fuels using renewable electricity. Among catalysts, Cu is unique in its ability to efficiently produce multi-carbon products, and nanoporous Cu (NPC) derived from brass dealloying has emerged as a promising candidate. However, fundamental understanding of both brass dealloying and CO₂RR mechanisms remains incomplete. This thesis advances knowledge in both areas.
In Chapter 3, we introduce CO Displacement, a new method to quantify active sites for CO(2)RR on Cu-based nanomaterials. Comparison with the conventional double-layer capacitance method across four nanostructured electrodes validated its accuracy. We confirm that electropolished Cu exhibits the highest intrinsic activity, and our findings suggest under-coordinated Cu atoms are the true active sites for CO₂RR. Chapter 4 explores NPC synthesis by chemical dealloying of Cu20Zn80 in 5 M H3PO4 at varied temperatures, yielding tuneable ligament sizes from tens of nanometres to micrometres. In situ synchrotron X-ray diffraction (XRD) and cryogenic-atom probe tomography (cryo-APT) reveal complex phase transformations during dealloying. We further propose a method based on XRD peak asymmetry to estimate under-coordinated atom density, expressed as ligament surface strain. Finally, electrochemical CO2 and CO reduction measurements using H-cell and electrochemical mass spectrometry (EC-MS) respectively demonstrate superior performance of NPC relative to polycrystalline Cu. A linear relationship between the CO intrinsic activity and ligament surface strain was found for CO2RR, and an optimal ligament surface strain value was also observed for the CO reduction of NPC on EC-MS. These results further suggest that under-coordinated Cu atoms are the active sites for CO(2)RR. Hence, this work establishes novel scientific methods for analysing nano-porous materials for electro-catalysis, with broad applicability to other nano-structured catalysts, as well as mechanistic insights into both dealloying of brass and electrochemical CO2 and CO reduction.
In Chapter 3, we introduce CO Displacement, a new method to quantify active sites for CO(2)RR on Cu-based nanomaterials. Comparison with the conventional double-layer capacitance method across four nanostructured electrodes validated its accuracy. We confirm that electropolished Cu exhibits the highest intrinsic activity, and our findings suggest under-coordinated Cu atoms are the true active sites for CO₂RR. Chapter 4 explores NPC synthesis by chemical dealloying of Cu20Zn80 in 5 M H3PO4 at varied temperatures, yielding tuneable ligament sizes from tens of nanometres to micrometres. In situ synchrotron X-ray diffraction (XRD) and cryogenic-atom probe tomography (cryo-APT) reveal complex phase transformations during dealloying. We further propose a method based on XRD peak asymmetry to estimate under-coordinated atom density, expressed as ligament surface strain. Finally, electrochemical CO2 and CO reduction measurements using H-cell and electrochemical mass spectrometry (EC-MS) respectively demonstrate superior performance of NPC relative to polycrystalline Cu. A linear relationship between the CO intrinsic activity and ligament surface strain was found for CO2RR, and an optimal ligament surface strain value was also observed for the CO reduction of NPC on EC-MS. These results further suggest that under-coordinated Cu atoms are the active sites for CO(2)RR. Hence, this work establishes novel scientific methods for analysing nano-porous materials for electro-catalysis, with broad applicability to other nano-structured catalysts, as well as mechanistic insights into both dealloying of brass and electrochemical CO2 and CO reduction.
Version
Open Access
Date Issued
2025-04-03
Date Awarded
01/10/2025
License URL
Advisor
Ryan, Mary
Stephens, Ifan
Publisher Department
Department of Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)