Simultaneous Operando Time-Resolved XAFS–XRD Measurements of a Pt/C Cathode Catalyst in Polymer Electrolyte Fuel Cell under Transient Potential Operations

Abstract

We have succeeded in simultaneous operando time-resolved quick X-ray absorption fine structure (QXAFS)–X-ray diffraction (XRD) measurements at each acquisition time of 20 ms for a Pt/C cathode catalyst in a polymer electrolyte fuel cell (PEFC), while measuring the current/charge of the PEFC during the transient voltage cyclic processes (0.4 VRHE → 1.4 VRHE → 0.4 VRHE) under H2(anode)–N2(cathode). The rate constants for Pt–O bond formation/dissociation, Pt charging/discharging, Pt–Pt bond dissociation/reformation, and decrease/increase of Pt metallic-phase core size under the transient potential operations were determined by the combined time-resolved QXAFS–XRD technique. The present study provides a new insight into the transient-response reaction mechanism and structural transformation in the Pt surface layer and bulk, which are relevant to the origin of PEFC activity and durability as key issues for the development of next-generation PEFCs.

Inhibitive effect of Pt on Pd-hydride formation of Pd@Pt core-shell electrocatalysts: An in situ EXAFS and XRD study

“…It is well established that Pt is a better HER catalyst than Pd and the onset potential for the HER is at more positive potentials for the Pt/C reference catalyst as seen in Fig. 4b, in agreement with Trasatti's original measurements [46] and the DFT calculations of Norskov et al [47] A study of the kinetics of H abs /hydride formation at the Pd@Pt catalyst electrodes using in situ time resolved EXAFS or XRD, such as those recently reported by Iwasawa's group for oxide formation at Pd@Pt catalysts [48] would be required to provide further comparison to this aspect of the thin film study by Bartlett and Marwan [45].…”

“…The lattice expansion of <0.6% observed, based on the in situ XRD measurements, was found for all of the core-shell catalysts. This is considerably less than the 3% increase observed for the Pd/C core at 0.0 V. Thus, it is unlikely that hydride formation occurring during surface area measurements in the accelerated aging tests or caused by hydrogen cross-over will be a significant driving force in the degradation of Pd@Pt core-shell catalysts when used in a membrane electrode fuel cell compared to the effects of oxide formation previously explored in accelerated aging studies [20,21] and, more recently, in combined time resolved EXAFS and XRD studies [48]. Table 2 Lattice parameters obtained by fitting the (220) Bragg peaks from the in situ XRD data (XRD) and calculated from the Pd-Pd coordination distance from the EXAFS fits for the catalyst electrodes in 0.5 mol dm À3 H 2 SO 4 .…”

Electrocatalytic water splitting at nitrogen-doped carbon layers-encapsulated nickel cobalt selenide

“…2 (b), (c) is high resolution transmission electron microscopy (HRTEM) images. The values of crystal lattice are 0.271, 0.182 and 0.340 nm, which correspond to characteristic lattice planes (101) and (100) of CoNiSe 2 and (111) of carbon respectively [36,37] . By using energy-dispersive X-ray (EDX) spectrum ( Fig.…”

Dynamics of oxide growth on Pt nanoparticles electrodes in the presence of competing halides by operando energy dispersive X-Ray absorption spectroscopy

“…The system is of particular complexity and the study of Pt oxidation itself has been at the basis of literature works since the early 70s' [5,6] and is still under investigation, also by means of sophisticated techniques, including synchrotron light-based ones [7][8][9][10][11].…”