Linking Multicomponent Interactions of Catalyst Ink and Catalyst Layer Fabrication with Electrochemical CO2 Reduction Performance

Abstract

The controllable fabrication of catalyst layers (CL) by tuning the multiscale structure formation is complex but vital to achieving optimum CO2 reduction (CO2R) performance. The CL formation is deeply influenced by catalyst ink. An in-depth understanding on the role of each catalyst ink component and how multicomponent interactions affect ink status, catalyst layer structure, and CO2R performance is crucial.In this work, the roles of various ingredients of catalyst ink were systematically investigated from simple binary inks to complete catalyst inks. Our results showed Ag agglomerates can be broken down more efficiently in water than in alcohols due to stronger inter-particle repulsive forces induced by water disassociation. Ag particles-Nafion networks were found to play a decisive role in stabilizing catalyst ink, mitigating agglomeration and particle sintering. The catalyst ink was comprehensively characterized and reported by static multiple light scattering (SMLS) for the first time in this study. The evolution of catalyst ink was identified in three stages: stable, flocculation and sedimentation. Isopropanol (IPA)-rich solvents were demonstrated to be more effective in stabilizing catalyst ink due to better dispersed Nafion aggregates and further enhanced Ag particle-Nafion interactions.Subsequently, catalyst layer structure and CO2R performance were correlated with multi-component interactions in catalyst ink. Strong Ag particle-Nafion interactions were proven to promote not only ink stability, but also catalyst layer homogeneity and reaction site distribution. Water-rich inks helped improve the porosity and durability of GDEs. The cathodic potential of GDEs made by 70%-water inks (-0.75 V vs. NHE) was 30% lower than zero-water inks (-1.1 V vs. NHE), and the highest CO selectivity was boosted to 97% at an industrial meaningful current density of 200 mA/cm2 by enhancing Ag particle-Nafion interactions through rational design of ink formulation, dispersing and fabrication processes.Simultaneously, a scalable manufacturing methodology of robust GDE was developed and validated to achieve optimal CO2R performance. It will not only provide a meaningful reference for lab applications (fast and reproducible GDE fabrication aiming at new catalysts, ionomers, membranes or operation conditions development), but also provide a steppingstone to industrial applications (GDE fabrication aiming at large scale, good durability and quality of conformance). Figure 1