A Ni based OER photoanode for CO 2 RR photoelectrochemical stacks Aureliano Macili 1* , Ruggero Bonetto 1,2 , Laia Francàs 1 , Jord García-Antón 1 , Xavier Sala 1 , Carolina Gimbert 1,2 1 Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193, Barcelona, Spain, 2 Centro de Innovació n en Química Avanzada (ORFEO-CINQA), Universitat Autò noma de Barcelona, Cerdanyola del Vallè s, 08193 Barcelona, Spain The electrochemical conversion of solar energy into energy carriers is expected to be a crucial component in the decarbonization of future societies. This approach utilizes catalytic processes to store renewable energy in chemical bonds. Carbon-based fuels and chemicals can be sustainably synthesized by electrochemically reducing carbon dioxide (CO2RR) at a cell’s cathode. In aqueous electrolytes, the CO2RR reactions are often paired by the Oxygen Evolution Reaction (OER) at the anode. While Ni-based catalysts are the benchmark for OER in alkaline electrolysis [1,2,3] , their performance declines in neutral and carbonate-rich conditions which are typical of CO2RR [4] . SOREC2, is an EU-funded initiative [5] which aims to pioneer technologies that convert solar photons and CO 2 directly into ethanol or ethylene. The project focuses on developing a compact tandem Photoelectrochemical Cell (PEC) incorporating a functionalized cathode designed to enhance selectivity toward C2 products. This work highlights the synthesis and characterization of a Ni-based OER catalyst and its use in photoanodes capable of operating under the stringent conditions of CO2RR. The catalyst is fabricated via an organometallic approach [6] and with the use of a bifunctional ligand, yielding a material embedded in a protective matrix that enhances stability at pH 7 and in carbonate environments. Additionally, its unique nanostructure facilitates binding to oxide-based semiconductors, enabling the fabrication of stable, transparent photoanodes essential for assembling the CO2RR-OER PEC. Comprehensive characterization of the catalyst and photoanodes has been conducted through various techniques, including operando XAS and high-resolution HAADF-STEM mapping, in collaboration with the ALBA 1. L. Yang, Z. Liu, S. Zhu, L. Feng, W. Xing, Ni-based layered double hydroxide catalysts for oxygen evolution reaction 2. Z. Yu, Y. Bai, G. Tsekouras, Z. Cheng, Recent advances in Ni-Fe (oxy)hydroxide electrocatalysts for the oxygen evolution reaction in alkaline electrolyte targeting industrial applications, Nano Select 3 (4) (2021)766–791. 3. E. S. Da Silva, A. Macili, R. Bofill, J. García-Antón, X. Sala, L. Francàs, Boosting the oxygen evolution activity of FeNi oxides/hydroxides by molecular and atomic engineering, Chemistry – A European Journal (Nov. 2023). 4. L.-F. Huang, et al. Improved Electrochemical Phase Diagrams from Theory and Experiment: The Ni−Water System and Its Complex Compounds, J. Phys. Chem. C 2017, 121, 9782−9789 5. Website: https://sorec2.eu/ 6. G. Martí, L. Mallón, N. Romero, L. Francàs, R. Bofill, K. Philippot,J. García-Antón, X. Sala, Surface-functionalized nanoparticles as catalysts for artificial photosynthesis, Advanced Energy Materials 13 (21) (Apr. 2023). synchrotron. References
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