Quantification of Active Sites on the Surface of PGM-free Catalysts

Laboratory: Los Alamos National Laboratory (LANL)
Capability Expert(s): Ulises Martinez, Scientist, 505-667-1802, ulisesm@lanl.gov
Siddharth Komini Babu, Post-Doc, 505-667-4641, skb@lanl.gov
Piotr Zelenay, Scientist, 505-667-0197, zelenay@lanl.gov
Capability Details:
Title:   Quantification of Active Sites on the Surface of PGM-free Catalysts
Class:   Characterization
Description:   By utilizing molecular probes to poison the catalyst, it is possible to identify the active site and estimate its density through in situ techniques. Molecular probes that can form a stable chemical adduct and can be removed from the active site surface electrochemically have been developed (1). Correlating the number of the probe molecules with the loss in measured activity after poisoning gives the number of active sites in a given material.
Capability Bounds:   The capability has been established only for rotating disk electrode and is being worked on for MEA.
Unique Aspects:   This is a unique technique relying on site-selective molecular/anionic probes crucial for correct estimation of the active sites.
Availability:   Please contact the team for instructions on shipping catalyst powder directly to LANL.
References:  
  1. P. Zelenay, D. Myers, ElectroCat (Electrocatalysis Consortium). 2017 DOE Annual Merit Review and Peer Evaluation Meeting.
  2. Journal publication is currently being written on this technique.
Benefit:   For further development of the PGM-free catalyst, there is a need for substantial increase in the active site density or the increasing the activity/turnover frequency (TOF). Hence, it is vital to identify the active site and understand its nature for a more targeted synthesis methodology to improve the performance of the PGM-free catalyst enabling commercial.
Robustness:    The technique is well established for RDE but is still in development for MEA. Tests are being conducted to adapt the technique to the MEA.
pair of graphs showing example
Left: The shift ORR performance of PGM-free catalyst when treated with the probe and the performance recovery after stripping the probe from the surface of the catalyst. Right: The stripping charge is calculated from the area under curve from the reductive stripping current curve.