Pt-Loaded MoO3 Nanorods as a Catalyst for Hydrogen Evolution and Oxygen Reduction Reactions in a Basic Medium

Abstract

The development of cost-efficient and effective electrocatalysts is highly needed for hydrogen evolution and oxygen reduction reactions (HER/ORR) for commercializing electrolyzer and fuel cell technologies. Addressing the sluggishness of alkaline HER and ORR kinetics is the key concern for the commercialization of electrolyzers and fuel cells. Platinum (Pt) is the state-of-the-art catalyst for the HER and ORR in a base. However, decreasing Pt loading without sacrificing its performance is still the key challenge. In this report, low Pt-loaded MoO₃ nanorods (Pt/MoO₃) were prepared for hydrogen evolution and oxygen reduction reactions in a base. The optimized catalyst, Pt_20%/MoO₃, shows a ∼40.6 mV overpotential in reaching −10 mA/cm² current density with 54.3 mV/dec Tafel slope for the HER. The catalyst also shows good stability and a ∼98% Faradic efficiency for hydrogen evolution. The catalyst also exhibited good ORR activity in the base. Pt_20%/MoO₃ attains a high half-wave potential of ∼0.87 V (RHE), a high onset potential of ∼1.017 V (RHE), and a long-term lifetime for oxygen reduction reaction due to the synergistic interaction between Pt and MoO₃. The catalyst exhibits better HER and ORR activities in comparison to Pt/C. Further, the rotating ring disk electrode (RRDE) measurements of the catalyst confirmed that the ORR reactions go through 4 e^– transfer processes. The HO₂^– production was found to be <10% during ORR, which is lower than that of commercial Pt/C. The optimal Pt coverage on MoO₃ nanorods and strong synergy between Pt and MoO₃ in Pt_20%/MoO₃ make it more effective compared to other synthesized catalysts. Therefore, this work offers valuable insight for designing low Pt-loaded electrocatalysts for use in electrolyzers, fuel cells, or other renewable energy devices.