Real‐time Monitoring Reveals Dissolution/Redeposition Mechanism in Copper Nanocatalysts during the Initial Stages of the CO₂ Reduction Reaction

Abstract

Size,m orphology,a nd surface sites of electrocatalysts have amajor impact on their performance.Understanding how, when, and why these parameters change under operating conditions is of importance for designing stable,a ctive,a nd selective catalysts.Herein, we study the reconstruction of aCubased nanocatalysts during the startup phase of the electrochemical CO 2 reduction reaction by combining results from electrochemical in situ transmission electron microscopyw ith operando X-ray absorption spectroscopy. We reveal that dissolution followed by redeposition, rather than coalescence, is the mechanism responsible for the sizei ncrease and morphology change of the electrocatalyst. Furthermore,w e point out the key role played by the formation of copper oxides in the process.U nderstanding of the underlying processes opens apathway to rational design of Cu electro (re)deposited catalysts and to stability improvement for catalysts fabricated by other methods.

In Situ Analytical Techniques for the Investigation of Material Stability and Interface Dynamics in Electrocatalytic and Photoelectrochemical Applications

“…[145][146][147][148][149][150][151][152] Furthermore, in situ TEM has been implemented to investigate materials involved in electrochemical processes, which is essential for understanding the operando structure-modified mechanisms of electrocatalysts. [153][154][155][156][157][158] For instance, Zhu et al used EC-TEM to gain deeper insight into the degradation mechanisms of Pt-Fe nanocatalysts. [153] They demonstrated that the coarsening processes of Pt-Fe electrocatalyst particles were not uniform, with the growth rate dependent on both the site and the applied potential.…”

“…Vavra et al used EC-TEM to study the reconstruction of Cu nanoparticle catalysts during the beginning phases of electrochemical CO 2 reduction. [155] As with similar EC-TEM studies, they used an electrochemical chip with a glassy carbon working electrode that provides a suitable support for the nanoparticle catalyst. This work indicated that Cu dissolution followed by redeposition, rather than coalescence, was the mechanism responsible for the observed size increase and morphological change of the electrocatalyst.…”

“…[ 145–152 ] Furthermore, in situ TEM has been implemented to investigate materials involved in electrochemical processes, which is essential for understanding the operando structure‐modified mechanisms of electrocatalysts. [ 153–158 ] For instance, Zhu et al. used EC‐TEM to gain deeper insight into the degradation mechanisms of Pt–Fe nanocatalysts.…”

Latent Mechanisms of Polarization Switching from In Situ Electron Microscopy Observations

“…The number of remaining latent variables is defined by the operator and here is typically set at 2. The rVAE's encoder had two convolutional layers with 128 filters ("kernels") of size (3,3) in each layer activated by leaky-ReLU function with a negative slope of 0.1. The rVAE's decoder consisted of two fully-connected ("dense") layers with 128 neurons in each layer activated by tanh().…”

“…For instance, liquid phase and electrochemical STEM have enabled observation of battery devices operation, [1] morphogenesis of the electrodeposition and electroplating, [2] and structural evolution during electrocatalysis. [3] Environmental STEM has offered insights into the mechanisms of nanoparticle and nanowire growth. [4] Finally, elementary mechanisms of beam-induced reactions in layered dichalcogenides and graphene, [5][6][7][8][9][10][11][12][13][14] as well as certain bulk materials, [15][16][17] have been obtained at the atomic level.…”