## 4 Conclusions  
Sn and Bi catalysts were successfully electrodeposited using the pulse plating method on top of and inside of the commercial and in-house fabricated GDLs.  
The electrodes were tested in an electrolysis cell at industrially relevant current densities up to 200 mA-cm\({}^{-2}\).  
It was found that the catalyst morphology determines the performance of the electrode. Inhomogeneous deposits provide more active centres for the CO\({}_{2}\) reduction reaction, resulting in an increased FE for formate.  
Upon CO\({}_{2}\) electrolysis at high current densities, complete dissolution of the electrodeposited Sn catalyst was observed. Furthermore, carbonate and bicarbonate formation was found inside of the GDLs.  
No leaching of the electrochemically deposited Bi catalyst on the in-house fabricated GDLs was observed during CO\({}_{2}\) electrolysis at high current densities. An FE of 94.2% towards formate was achieved in these electrodes.  
Such electrodes also have promising long-term stability (23 h) for the eCO\({}_{2}\)RR at industrially relevant current densities (200 mA-cm\({}^{-2}\)) and have a very good selectivity for formate.  
**Supplementary Materials:** The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app13137471/s1](https://www.mdpi.com/article/10.3390/app13137471/s1)]([https://www.mdpi.com/article/10.3390/app13137471/s1](https://www.mdpi.com/article/10.3390/app13137471/s1)): Figure S1: Investigations of Bi-IH-PP ODEs. (a) SEM image of Bi-IH-PP, Bi-10-11-15; (b) SEM image of Bi-IH-PP, Bi-5-11-30; (c) CT image of Bi-IH-PP, Bi-5-55-140. Table S1: Potentials of the electrodes shown in Figure 1a-c. Table S2: Potentials of the electrodes shown in Figure 4 (1-6). Table S3: Potentials of the electrodes shown in Figure 5a-c. Figure S2: EDX-spectra of Bi-IH-PP, Bi-5-55-140 GDE after eCO\({}_{2}\)RR at 200 mA-cm\({}^{-2}\), 50 \({}^{\circ}\)C, 60 min. Figure S3: (a) Spectra 6 and (b) Spectra 5. Figure S4: Potentials of Figure 6. Potentials of Bi-IH-PP PDE, Bi-5-55-140 (blue) with Bi-IH-P PDE (red). Tested at 200 mA-cm\({}^{-2}\), 50 \({}^{\circ}\)C, 24 h. Figure S5: The FE for formate and product distribution for electrodes with electrodeposited catalysts Bi-BC-PP (15-11-10), shown in column (a); the electrodeposited catalysts Bi-IH-PP (15-55-20), shown in column (b); and an electrode with a precipitated Bi catalyst, shown in column (c). Electrochemical tests conditions: 200 mA-cm\({}^{-2}\), 50 \({}^{\circ}\)C, time on stream (TOS): 60 min. Figure S6: XRD measurements of Bi-BC-PP SDE Bi-15-11-10 after eCO\({}_{2}\)RR (50 mA-cm\({}^{-2}\), 50 \({}^{\circ}\)C, 24 h). Figure S7. XRD measurements of Bi-BC-PP SDE Bi-15-11-10 after eCO2 RR (50 mA-cm\({}^{-2}\), 50 \({}^{\circ}\)C, 24 h). Figure S8. (a) GDL (Spectra 6); (b) GDL (Spectra 5).  
**Author Contributions:** Conceptualization, E.K. and S.S.; investigation, M.M., J.H. and S.H.; writing--original draft preparation, M.M. and J.H., writing--review and editing, S.S. and E.K.; supervision, E.K. and H.K.; project administration, M.M. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the German Federal Ministry for Economic Affairs and Climate Action under grant number AiF/IGF 47 EWN.  
**Institutional Review Board Statement:** This study did not require ethical approval.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors thank [PERSON], who provided review and editing assistance during the composition of the manuscript.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.