# Experimental and Modeling Study for the Solar-Driven CO2 Electrochemical Reduction to CO
## 4 Conclusions and Practical Recommendations  
A PV-EC system, consisting of a module of DSSCs and a batch cell reactor with Ag nanoparticles as cathodic electrocatalysts, is presented. The device can efficiently convert CO\({}_{2}\) to CO with no external energy input other than sunlight, and its performance has also been demonstrated in dimmer light conditions for outdoor applications in different weather conditions. In particular, a FE = 73.85% was achieved for CO production with a  
Figure 5: Current density and faradaic efficiency of the PV–EC device (**a**) and overall cell voltage (**b**) as a function of the incident power. Figure 6: Experimental (**a**) and simulated (**b**) chronoamperometry of the PV–EC device under 1 SUN illumination. current density J = 3.35 mA/cm\({}^{2}\) at 1 sun of illumination, while FE = 68.5% and FE = 64.1% were achieved with 0.8 and 0.6 suns, respectively. A complete model has been developed, as well, for the whole PV-EC device, demonstrating good agreement when reproducing the experimental data. The present work paves the way for real weather conditions for PV-EC devices, along with the development of more complex models for the solar-driven CO\({}_{2}\)RR. For instance, this work shows quantitative data that can be exploited to address the lower performance of the CO\({}_{2}\)RR at a lower incident power, which can be helpful in engineering the device in out-of-laboratory conditions. Since Ag nanoparticles are a well-established catalyst that can reach higher current densities in the CO\({}_{2}\)RR [27], the limited current densities achieved with the batch cell reactor can be improved by exploiting different reactors, like zero-gap reactors. Nevertheless, in the PV-EC field, higher current density requirements must be fulfilled by bigger PV systems. For this purpose, the feasibility of the device demonstrated by the experimental data, combined with a suitable modeling approach to support the system's scaling-up process, makes this work valuable for advancing integrated systems like the artificial leaf towards increasingly higher operating electrical points. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app15020549/s1](https://www.mdpi.com/article/10.3390/app15020549/s1)]([https://www.mdpi.com/article/10.3390/app15020549/s1](https://www.mdpi.com/article/10.3390/app15020549/s1)), Figure S1: Faradaic efficiency as a function of the voltage applied in a 2-electrode configuration; Figure S2: Current density as a function of the voltage applied in a 2-electrode configuration. Table S1: Kinetic parameters for electrochemical reactions. M.A. : Writing--review and editing, Writing--original draft, Investigation, Methodology, Data curation, Validation, Conceptualization. R.S. : Methodology, Writing--review and editing. A.L. : Resources, Writing--review & editing. C.F.P. : Project administration, Resources, Writing--review and editing. A.S.: Conceptualization, Data curation, Methodology, Supervision, Writing--review and editing. All authors have read and agreed to the published version of the manuscript. This research was funded by the Italian Ministry of Education (MUR): the Ph.D. fellowship was funded under the National Research and Innovation Operational Program 2014-2020 (CCI 2014 IT16M2 OP005), ESF REACT-EU resources, Action IV.4 \"Doctorates and research contracts on innovation topics\", and Action IV.5 \"Doctorates on Green topics\". The project \"Network 4 Energy Sustainable Transition--NEST\", Spoke 4, Project code PE0000021 was funded under the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.3--Call for tender No. 1561 of 11.10.2022 of Ministero dell'Universita' e della Ricerca (MUR); funded by the European Union--NextGenerationEU. With the support of the 'Fondazione Compagnia di San Paolo', as part of the VEIColo--Line 1 grant program.