We derive fundamental understanding of the incorporation of IIIA group elements (viz, B, Al and Ga) in the pristine copper nanoclusters and their reactivity towards CO2 and CO activation with the aid of DFT based methodologies. Further, we established the electrochemical CO2 reduction facility equipped with real-time gas chromatography to measure hydrocarbons and also established the standard protocols for NMR measurements to quantify the liquid-oxygenates at the host institute. Experimentally, shape and size selective chloride-free nanocubes were produced on various substrates such as glassy carbon, Au, TiN/TiON surfaces by employing pulse-electrodeposition. These nanocubes on glassy carbon exhibited selective methane formation (Faradaic efficiency of 31.7%) by appropriate electrochemical protocols (become part of the PhD thesis of one student). Whereas, FE of 20% was achieved without any appropriate electrochemical protocol on Cu octahedras, owing to geometry corresponding to (111) surfaces. Furthermore, by using temperature programmed solid-state decomposition methodology we produced quasi-spherical and nanowires of copper. These nanowires, unique ternary heterointerface of C-Cu2O-Cu, demonstrated selective ethylene (major product) formation (FE of 25%) owing to the heterointerfacial effect. All the nanostructures were fully characterized with the aid of XRPD, Raman, HR-TEM, STEM, XPS, XAES and IL-SEM.
To describe and corroborate our findings we have used conceptual DFT based reactivity descriptors such as Fukui functions, chemical hardness and potential, global electrophilicity index, electronegativity, spin density distribution, electrostatic potential mapping, change in enthalpy of adsorption and free energy along with binding energies and relative energies wherever necessary. The activation of CO is further confirmed by IR stretching frequency, bond length, and extent of charge transfer. Moreover, to better understand the proton coupled electron transfer (PCET) at the electrochemical interface we have also considered few reactive intermediates (RIs) such as *COOH, *H, *COH, and *CHO (to name a few). All these RIs are selected to better understand the interfacial phenomena where product selectivity, HER suppression, and bifurcation pathways for liquid oxygenates and hydrocarbons. In summary, IIIA group elements-doped copper nanoclusters are better in activating CO2/CO, and in stabilizing RIs compared to pristine nanoclusters. Thus, we can design better electrocatalysts by fine-tuning the electronic structure of copper for efficient, selective and stable electrocatalysis in near future.
Dissemination plan for this MSC action included reports targeting at material scientists, specific to CO2 catalysis community and the broader audience from till schools to general public. Specifically, two scientific publications in peer-reviewed journals have been published. Three more publications are still underway from this project in high-impact peer-reviewed journals. Especially the work with nanowires, a unique ternary heterointerface is expected to be the game changer in the community of CO2 electrocatalysis. Moreover, I have participated in four international conferences and workshops (with two posters and two oral presentations). In addition, I have also given lectures at the various departments of the host institution.
