Electrochemical reduction of CO₂ into chemical fuels by using renewable electricity is an attractive option in controlling the atmospheric CO₂ concentration and storing natural energy. Currently, its wide applications have been hindered by the unsatisfactory performance of electrocatalysts, including the dispersive product selectivity, sluggish reaction kinetics, and large overpotentials. To accelerate the practical applications of this technique, both the synthesis of novel catalytic materials and insightful understandings of the catalyst composition and structure effects on the catalytic performance should be highlighted.

In this thesis, one part of the major efforts has been made in the development of high-performance electrocatalysts for CO₂-to-CO conversion. Two types of Au-Pd bime...[ Read more ]

Electrochemical reduction of CO₂ into chemical fuels by using renewable electricity is an attractive option in controlling the atmospheric CO₂ concentration and storing natural energy. Currently, its wide applications have been hindered by the unsatisfactory performance of electrocatalysts, including the dispersive product selectivity, sluggish reaction kinetics, and large overpotentials. To accelerate the practical applications of this technique, both the synthesis of novel catalytic materials and insightful understandings of the catalyst composition and structure effects on the catalytic performance should be highlighted.

In this thesis, one part of the major efforts has been made in the development of high-performance electrocatalysts for CO₂-to-CO conversion. Two types of Au-Pd bimetallic nanocatalysts (twisted nanowires and nanoparticles) consisting of atomic thin layers of Pd (Pd-rich) shell and Au-Pd alloy core are developed. The optimized catalyst can selectively convert CO₂ to CO (>94% selectivity) at low overpotentials (390 mV), along with an ultrahigh mass activity (100 A g^-1_catalyst). As confirmed by the powerful in situ infrared absorption spectroscopy, both the grain boundaries and core-shell structures can enhance the activation of CO₂ molecules to *COOH intermediates and lower the overpotential. The incorporation of Au atoms in the core can further facilitate the desorption of *CO intermediates and increase the overall reaction kinetics. These studies provide useful principles on the rational design of more advanced core-shell electrocatalysts.

In additional, fundamental understandings of the electrochemical interfaces on carbon-based single iron atom catalyst (Fe-N-C) and Cu thin film surfaces are also obtained by combining in situ infrared absorption spectroscopy, electrochemical techniques, and theoretical calculations. The major findings include: 1) the observation of bicarbonate anion-mediated CO₂ mass transport phenomenon; and 2) the observation of Fe-N₄ moieties embedded in complete graphene structure (i.e. the most widely believed active sites) as permanently poisoned sites in CO₂-to-CO conversion. These findings add significantly new insights into CO₂ reduction mechanisms.