Cu‐containing metalloenzymes are known to catalyze oxygen activation through cooperative catalysis. In the current work, we report the design of synthetic polymer Cu catalysts using pyrene‐labelled poly(2‐hydroxy‐3‐dipicolylamino) propyl methacrylate (Py‐PGMADPA) to coordinate multiple Cu sites along polymer chains. The catalysts feature a pyrene end group that can form supramolecular π‐π stacking with conductive carbon to allow efficient immobilization of catalysts to the graphite electrode. Cu‐containing Py‐PGMADPA was examined for electrocatalytic oxygen reduction. The hybrid catalyst showed an onset potential of 0.5 V (vs. RHE) at pH 7 and 0.79 V at pH 13. The kinetic study indicated that the catalyst had a 2e−reduction of oxygen mainly mediated by Cu+centers. We demonstrated the importance of cooperative catalysis among Cu sites which did not exist for other transition metal ions, like Mn2+, Fe2+, Co2+, and Ni2+. The confinement of polymer chains promotes the activity and stabilizes Cu catalysts even at an extremely low Cu loading. The rational design of bioinspired polymer catalysts offers an alternative way to prepare synthetic mimics of metalloenzymes.
High entropy spinel oxide for efficient electrochemical oxidation of ammonia
Ammonia has emerged as a promising energy carrier owing to its carbon neutral content and low expense in long-range transportation. Therefore, development of a specific pathway to release the energy stored in ammonia is therefore in urgent demand. Electrochemical oxidation provides a convenient and reliable route to attain efficient utilization of ammonia. Here, we report that the high entropy (Mn, Fe, Co, Ni, Cu)3O4 oxides can achieve high electrocatalytic activity for ammonia oxidation reaction (AOR) in non-aqueous solutions. The AOR onset overpotential of (Mn, Fe, Co, Ni, Cu)3O4 is 0.70 V, which is nearly 0.2 V lower than that of their most active single metal cation counterpart. The mass spectroscopy study reveals that (Mn, Fe, Co, Ni, Cu)3O4 preferentially oxidizes ammonia to environmentally friendly diatomic nitrogen with a Faradic efficiency of over 85%. The X-ray photoelectron spectroscopy (XPS) result indicates that the balancing metal d-band of Mn and Cu cations helps retain a long-lasting electrocatalytic activity. Overall, this work introduces a new family of earth-abundant transition metal high entropy oxide electrocatalysts for AOR, thus heralding a new paradigm of catalyst design for enabling ammonia as an energy carrier.
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- Award ID(s):
- 1954838
- NSF-PAR ID:
- 10277201
- Date Published:
- Journal Name:
- Nano Research
- ISSN:
- 1998-0124
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s12274-021-3665-8
