Journal Article

PUBDB-2023-00392

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png In Situ Mechanistic Insights for the Oxygen Reduction Reaction in Chemically Modulated Ordered Intermetallic Catalyst Promoting Complete Electron Transfer

Mondal, S. ; Bagchi, D.Extern* ; Riyaz, M. ; Sarkar, S.Extern* ; Singh, A. K. ; Vinod, C. P. ; Peter, S. C. (Corresponding author)

2022
ACS Publications Washington, DC

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Please use a persistent id in citations: doi:10.1021/jacs.2c04541

Abstract: The well-known limitation of alkaline fuel cells is the slack kinetics of the cathodic half-cell reaction, the oxygen reduction reaction (ORR). Platinum, being the most active ORR catalyst, is still facing challenges due to its corrosive nature and sluggish kinetics. Many novel approaches for substituting Pt have been reported, which suffer from stability issues even after mighty modifications. Designing an extremely stable, but unexplored ordered intermetallic structure, Pd$_2$Ge, and tuning the electronic environment of the active sites by site-selective Pt substitution to overcome the hurdle of alkaline ORR is the main motive of this paper. The substitution of platinum atoms at a specific Pd position leads to Pt$_{0.2}$Pd$_{1.8}$Ge demonstrating a half-wave potential (E$_{1/2}$) of 0.95 V vs RHE, which outperforms the state-of-the-art catalyst 20% Pt/C. The mass activity (MA) of Pt$_{0.2}$Pd$_{1.8}$Ge is 320 mA/mg$_{Pt}$, which is almost 3.2 times better than that of Pt/C. E$_{1/2}$ and MA remained unaltered even after 50,000 accelerated degradation test (ADT) cycles, which makes it a promising stable catalyst with its activity better than that of the state-of-the-art Pt/C. The undesired 2e$^–$ transfer ORR forming hydrogen peroxide (H$_2$O$_2$) is diminished in Pt$_{0.2}$Pd$_{1.8}$Ge as visible from the rotating ring-disk electrode (RRDE) experiment, spectroscopically visualized by in situ Fourier transform infrared (FTIR) spectroscopy and supported by computational studies. The effect of Pt substitution on Pd has been properly manifested by X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS). The swinging of the oxidation state of atomic sites of Pt$_{0.2}$Pd$_{1.8}$Ge during the reaction is probed by in situ XAS, which efficiently enhances 4e$^–$ transfer, producing an extremely low percentage of H$_2$O$_2$.

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)

Research Program(s):

1. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
2. INDIA-DESY - INDIA-DESY Collaboration (2020_Join2-INDIA-DESY) (2020_Join2-INDIA-DESY)

Experiment(s):

1. PETRA Beamline P64 (PETRA III)

Appears in the scientific report 2022

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