Correlating catalyst ink design and catalyst layer fabrication with electrochemical CO2 reduction performance

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The controllable fabrication of catalyst layers (CL) by tuning the multiscale structure formation is complex but vital to achieving optimum carbon dioxide reduction (CO2R) performance. An in-depth understanding on the role of each catalyst ink component and how multi-component interactions affect ink status, catalyst layer structure, and CO2R performance is crucial. In this work, the roles of different ingredients of catalyst ink were systematically investigated from simple binary inks to complete catalyst inks. Silver (Ag) particles-Nafion interactions 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 paper. The evolution of catalyst ink was identified in three stages: stable, flocculation and sedimentation. Isopropanol (IPA)-rich solvents were found 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. The carbon monoxide (CO) selectivity was boosted from 80.5 % to 94 % at an industrial meaningful current density of 200 mA/cm2 using commercial Ag nanoparticles by rational design of ink formulation, dispersing and fabrication processes. Simultaneously, a scalable manufacturing methodology of robust gas diffusion electrodes (GDEs) to achieve optimal CO2R performance was developed and validated.