Identification of Carbon Dioxide Electroreduction Products on Multilayered Metallic Catalysts Based on Palladium

Atmospheric carbon dioxide levels have risen rapidly over the last few decades. Electrochemical conversion of carbon dioxide into eligible fuels has potential as a technology that may prevent from a serious environmental problems. Electroreduction of carbon dioxide to hydrocarbons is a complex process that usually involves adsorbed carbon monoxide as an intermediate. The overall electroreduction path is determined to a large extent by the catalyst’s surface affinity to carbon monoxide and hydrogen. Strongly bounded CO inhibits further reduction while weakly bounded CO easily desorbs as a final product [1]. One of primary step is CO 2 adsorption followed by its reduction to absorbed carbon monoxide. The presences of adsorbed atomic hydrogen at the catalyst surface can significantly facilitate the formation of hydrocarbons. However, within the potential range of CO 2 reduction in the aqueous solution a competitive reaction of hydrogen evolution (HER) takes place, which can even dominate in the electroreduction processes. Our result points out the possibility of tuning catalyst’s affinities to both hydrogen and CO by designing multilayered structures obtained by sequential UPD strategies [2]. Results show that catalytic activity can be finely tuned by using the multilayered near-surface-alloy approach [3]. Our results clearly demonstrate that the Pd-layer thickness and location significantly changes the surface catalytic activity of palladium toward CO 2 electroreduction. Interestingly, multilayered films covered with the silver monolayer largely reflect the properties of palladium deposits existing under the Ag surface. Differential Electrochemical Mass Spectrometry method (DEMS) was used to analyze and determine gaseous products of carbon dioxide electroreduction together with evolved hydrogen. Individual molecules are recognized by ionic current mass signals. DEMS method allows to identify reduction products during faradaic reduction [4]. This technique is particularly useful for investigations of electroinactive molecules such as methane or ethylene. Ion current changes are related to applied potential, and were presented as MS-CV (mass spectrum cyclic voltammograms). MS-CV provide useful information on the formation potentials of each products. Electroactive products and intermediates, such as carbon monoxide and formic acid were also detected by using classical electrochemical methods. For this purpose a palladium electrode was used for detection of CO