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oai:figshare.com:article/34037311 2026-10-01T00:11:07Z category_1 category_4 category_12 category_21 category_24 category_873 category_734 portal_63 item_type_6 month_year_10_2026

High-Performing Unitized Regenerative Fuel Cell Using PGM-Free Bifunctional Catalysts from Waste-Derived Carbon Eva Sousa (25147123) Sofia Delgado (14496098) Fátima Santos (7011518) Adélio Mendes (1463563) Biophysics Biochemistry Cell Biology Biotechnology Evolutionary Biology Chemical Sciences not elsewhere classified Biological Sciences not elsewhere classified selected electrodes toward particularly noteworthy considering oxygen reduction reaction oxygen evolution reaction nucleating either fe crms ), demonstrated circular economy principles 35 %, respectively 3 wt %. maximum metal loading efficient bifunctional catalysts benchmark commercial catalysts potential window range ninc catalyst showed free alkaline electrolytes doped carbon supports critical raw materials based waste product 4 </ sub 3 </ sub free bifunctional catalysts ninc catalysts ca </ ultralow loading doped carbons catalyst demonstrates carbon precursor free catalysts wave potential trip efficiency term performance sustainable approach stress test slow kinetics promising technology phenolic resin outstanding compromise onset potential oer ). noble pt greatly dependent enhanced properties energy storage e ., developing innovative cell operation Unitized regenerative alkaline-exchange membrane fuel cells (UR-AEMFCs) are a promising technology for energy storage, attending to their ability to operate in both galvanic (FC) and electrolytic (WE) modes. However, their round-trip efficiency (RTE) is greatly dependent on the selected electrodes toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). As both mechanisms have slow kinetics, developing innovative and efficient bifunctional catalysts is critical to increasing UR-AEMFC performance. In this work, bifunctional precious group metal-free (PGM-free) catalysts were prepared by nucleating either Fe, Ni, or FeNi on nitrogen-doped carbons; the prepared catalysts have a maximum metal loading of up to 3 wt %. To align with circular economy principles, a sustainable approach was employed by using a phenolic resin-based waste product as a carbon precursor. The carbonization process, conducted in the presence of H₃PO₄ and melamine, yielded nitrogen-doped carbon supports with enhanced properties. Notably, in single-cell operation, the prepared PGM-free catalystsNiNC, FeNC, and FeNiNCgenerated RTEs of 29%, 38%, and 35%, respectively, under corrosion-free alkaline electrolytes (0.5 M KOH); similar results were reported for benchmark commercial catalysts such as IrO₂, which displayed <i>ca</i>. 30% of RTE. Moreover, NiNC catalyst showed a half-wave potential of 0.74 V, an onset potential of 0.88 V, and an overpotential of 420 mV at 10 mA cm^–2. In turn, the FeNC displayed a half-wave potential of 0.72 V, an onset potential of 0.90 V, and an overpotential of 510 mV at 10 mA cm^–2. Regarding the FeNiNC, this catalyst demonstrates a half-wave potential of 0.76 V, an onset potential of 0.86 V, and an overpotential of 380 mV at 10 mA cm^–2. These results are particularly noteworthy considering the significantly lower metal loadings in the produced PGM-free catalysts. Besides, to evaluate their long-term performance, the single cell was submitted to several potential cycles within the potential window range for FC and WE modes, i.e., between 0.6 and 2.0 V. The noble Pt/C catalysts deactivated completely after the stress test, while the novel FeNiNC and NiNC catalysts, containing an ultralow loading of critical raw materials (CRMs), demonstrated an outstanding compromise between activity and stability, proving their potential to be integrated in UR-AEMFC. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/acsomega.6c07541.s001 https://figshare.com/articles/journal_contribution/High-Performing_Unitized_Regenerative_Fuel_Cell_Using_PGM-Free_Bifunctional_Catalysts_from_Waste-Derived_Carbon/34037311 CC BY-NC 4.0