Jorge Montero

Rechargeable Zn–air batteries (ZABs) can play a significant role in the transition to a cleaner and more sustainable energy system due to their high theoretical energy density, high cell voltage, and environmental friendliness. ZAB’s air cathode is the principal determinant in predicting the battery’s overall performance, as it is responsible for catalyzing the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during the discharging and charging process, respectively. In this work, a detailed optimization study of the architecture of the air cathode was carried out using the benchmark bifunctional oxygen electrocatalyst (Pt/C-RuO₂). The air cathode composition and architecture were optimized regarding the choice of the commercial gas diffusion layer (GDL), the effect of hot pressing the catalyst layer (CL), and the optimum pore size of the current collector. The best cathode from this study shows a maximum power density (PD_max) of 167 mW/cm², with a round trip efficiency and a voltage gap (E_gap) of 59.8% and 0.78 V, respectively, indicating the air cathodes preparation approach proposed in this work as a promising strategy for the improvement of the overall performance of ZABs.

Aqueous organic redox flow batteries (AORFBs) have gained increasing attention for large‐scale storage due to the advantages of decoupled energy and power, safe and sustainable chemistry, and tunability of the redox‐active species. Here, we report the development of a neutral‐pH AORFB assembled with a highly water‐soluble ferrocene 1,1‐disulfonic disodium salt (DS−Fc) and two viologen derivatives, 1,1’‐bis(3‐sulfonatopropyl)‐viologen (BSP−Vi) and Bis(3‐trimethylammonium)propyl viologen tetrachloride (BTMAP−Vi). Synthesized electrolytes showed excellent redox potential, good diffusion coefficient, and a good transfer rate constant. In particular, BSP−Vi has a more negative redox potential (‐0.4 V) than BTMAP−Vi (−0.3 V) and faster kinetics; therefore, it was selected to be assembled in an AORFB as anolyte, coupled with DS−Fc as catholyte.The resulting AORFB based on BTMAP−Vi/DS−Fc and BSP−Vi/DS−Fc redox couple had a high cell voltage (1.2 V and 1.3 V, respectively) and theoretical energy density (13 WhL⁻¹ and 14 WhL⁻¹ respectively) and was able to sustain 70 charge‐discharge cycles with energy efficiency as high as 97 %.