Copper-based nanostructured catalysts for efficient and selective CO2 electroreduction – synthesis, catalytic performance, and mechanistic analysis

In the past decades, the atmospheric CO2 emissions increased with the unrestrained combustion of fossil fuels to meet the growing energy demand, leading to serious environmental pollution and climate issues. The electrochemical CO2 reduction reaction (CO2RR) is a promising alternative to convert CO2 into value-added products, and has the potential to contribute to a carbon-neutral energy cycle by using surplus electricity generated from renewable sources (e.g., solar and wind). Among various materials, copper-based catalysts are most studied, given their unique capability to make hydrocarbons in considerable amounts and at reasonable overpotentials. In this thesis, in-depth understanding of the CO2 electroreduction process was firstly established by adjusting the local reaction environment of a CuOx nanoparticle (NP) model catalyst. A tunable product distribution during catalytic CO2 electroreduction could be achieved by varying areal particle densities and co-feeding CO2 reactant with CO. With higher areal density and lower mean interparticle distances, a shift in faradic efficiency towards C2H4 over CH4 was observed, which was attributed to enhanced CO(g) re-adsorption on catalyst surface sites in close proximity. Furthermore, the electroreduction of CO2 feed with CO-bleeding showed enhanced ethylene production over a broad potential range with various co-feed ratios. The origin of the carbon-atoms in C2H4 under co-feed conditions was traced and quantified by a custom-designed operando differential electrochemical mass spectrometry (DEMS) flow cell, giving unique mechanistic insight in the CO2-CO co-feed system. The co-feed mechanism was extended to novel tandem catalysts, in which a CO producer (Ag, or NiNC) works as local CO feeding source and combines with Cu-based catalysts, showing obvious enhancement in ethylene production compared to purely copper-based systems. Furthermore, a sheet-shaped CuOx catalyst was designed, developed and systematically investigated. In H-Cell measurements, a high activity for CO2RR could be observed, followed by tests in a micro flow cell, demonstrating a record C2H4 partial current density of 229 mA cm 2 and a C2+ partial current density of ~ 410 mA cm-2. Moreover, a combination of operando/(quasi) in situ XAS, WAXS, DEMS, S/TEM techniques were employed to discover structure-activity-selectivity relations under catalytic CO2RR operating conditions, delivering perspectives to design novel catalysts to produce hydrocarbons as the value-added products.

Author dc:creator

• Wang, Xingli

Advisor dc:contributor.advisor

• Strasser, Peter

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.14279/depositonce-9882

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/10990