UC Irvine

Non-precious group metal electrocatalysts are explored for CO2 reduction. Carbon-based metal-nitrogen-carbon (M-N-C) catalysts are investigated and tested via a handmade microfluidic flow cell. Copper-based catalysts are also explored for the reduction of CO2 as so far as how the solvent and acidic/basic moiety dopant content may influence the observed performance. The M-N-C catalysts are explored based on the sacrificial support method (SSM) which was developed by the Atanassov Lab in 2008. A bifunctional bi-metallic M-N-C is developed and studied for syngas production. Finally, a novel synthesis method for M-N-C catalysts is presented which is a one-pot synthesis that produces catalysts with comparable or improved activity for CO2 reduction compared to the state-of-the-art and SSM catalysts. This novel synthesis may be tailored for a range of electrocatalytic applications. As such, it is an industry disrupting technology due to its requiring no harsh solvents of any kind as well its industrial scalability. The materials characterization is explored using standard analytic methods such as transmission electron microscopy (TEM), and X-Ray Diffraction (XRD). The elemental mapping of the catalysts is explored via energy dispersive X-ray spectroscopy (EDS). X-ray Photoelectron spectroscopy (XPS) is used for assessing the surface chemical changes of the catalysts. Scanning electron microscopy (SEM), combined with BET adsorption studies, Raman spectroscopy, and studies of the metal coordination sphere(s) using XANES/NEXAFS are also employed. The electrochemical characterization is carried out using voltametric techniques: linear sweep voltammetry (LSV), cyclic voltammetry (CV), potentiostatic electrochemical impedance spectroscopy (PEIS), and chronoamperometry (CA). The gas-phase product distribution is explored via gas chromatography and the liquid-phase product distribution is assessed by 1H NMR. The material/electrochemical techniques are used in tandem to suggest possible electrocatalytic mechanism and reasons for the observed activity/selectivity. The catalyst development is approached from one of two perspectives: either i.) to gain theoretical and fundamental physical insight to the heterogeneous electrocatalytic process itself or ii.) to assess the possibility for the catalysts to be explored for industrial applications. Addressing the second point, the ease of manufacturability as well as the robustness of the developed catalysts are considered. Finally, a novel Ni-N-C catalyst is developed which shows unmatched selectivity for CO production at both high overpotential and low overpotential. Conventionally and before this catalyst, Ni-N-C was only able to achieve high selectivity at high overpotential. The novel Ni-N-C synthesized here shows > 85 % faradaic efficiency for CO formation (FECO) at -0.3 V vs. RHE and > 99 % FECO at -1.1 V vs. RHE.