Enhancing Trifunctional Electrocatalytic Activities via Lanthanide Modulation in Fe-Co-Based Double Perovskite Oxides

In the global development of alternative and sustainable fuels, H₂ has gained prime research interest as combustion of it results in energy with zero carbon footprint. In this context, non-noble metal-based double perovskite oxides with their wide tunable structure gained interest from researchers as an effective electrocatalyst for water oxidation in alkaline medium. However, their low catalytic efficacy and durability limit their application for the industrial scale. Here, we present several Fe-Co-based double perovskite oxides tuning their A-site with lanthanides for overall water splitting and hybrid electrolysis for energy-saving H₂ production. The best Fe-Co-based double perovskite oxide, Eu₂FeCoO₆, demonstrates very high trifunctional electrocatalytic activity for oxygen evolution reaction (OER) and small alcohol molecule oxidation, along with hydrogen evolution reaction (HER). Overpotentials (η₁₀) of 220 mV for the OER and 238 mV for the HER were attained at 10 mA cm^-2 current density in 1 M NaOH (pH = 14). Also, Faradaic yields of 85 and 89% were achieved for ethanol oxidation (EtOR) and benzyl alcohol oxidation (BnOR), respectively, with the best catalyst. Moreover, in a two-electrode electrolyzer with 0.1 M benzyl alcohol (as an electrolyte) and Eu₂FeCoO₆ as a bifunctional catalyst (both as the cathode and anode, Eu₂FeCoO₆ (−)∥Eu₂FeCoO₆ (+)), a cell potential of 1.75 V was enough for oxygenation of benzyl alcohol along with the production of H₂. A 150 mV advantage in cell potential was gained in BnOR-aided H₂ generation compared with overall water oxidation.