Volume 62, Issue 35 e202305719
Research Article

Supramolecular Enhancement of Electrochemical Nitrate Reduction Catalyzed by Cobalt Porphyrin Organic Cages for Ammonia Electrosynthesis in Water**

Dr. Lun An

Dr. Lun An

Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720-1460 USA

Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720-1460 USA

Search for more papers by this author
Dr. Mina R. Narouz

Dr. Mina R. Narouz

Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720-1460 USA

Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720-1460 USA

Search for more papers by this author
Dr. Peter T. Smith

Dr. Peter T. Smith

Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720-1460 USA

Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720-1460 USA

Search for more papers by this author
Patricia De La Torre

Patricia De La Torre

Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720-1460 USA

Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720-1460 USA

Search for more papers by this author
Prof. Christopher J. Chang

Corresponding Author

Prof. Christopher J. Chang

Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720-1460 USA

Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720-1460 USA

Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, 94720-1460 USA

Search for more papers by this author
First published: 06 July 2023
Citations: 17
**

A previous version of this manuscript has been deposited on a preprint server (https://doi.org/10.26434/chemrxiv-2022-09q8t-v2).

Graphical Abstract

We present a supramolecular strategy for electrochemical nitrate reduction by augmenting porosity and electrochemically active sites as well as facilitating catalyst-substrate interactions. The resulting 3D architecture enables selective ammonia production in water with greater than 90 % Faradaic efficiency and turnover numbers exceeding 200,000, representing a 15-fold increase in activity and higher catalytic stability over its 2D counterpart.

Abstract

The electrochemical nitrate (NO3) reduction reaction (NO3RR) to ammonia (NH3) represents a sustainable approach for denitrification to balance global nitrogen cycles and an alternative to traditional thermal Haber-Bosch processes. Here, we present a supramolecular strategy for promoting NH3 production in water from NO3RR by integrating two-dimensional (2D) molecular cobalt porphyrin (CoTPP) units into a three-dimensional (3D) porous organic cage architecture. The porphyrin box CoPB-C8 enhances electrochemical active site exposure, facilitates substrate–catalyst interactions, and improves catalyst stability, leading to turnover numbers and frequencies for NH3 production exceeding 200,000 and 56 s−1, respectively. These values represent a 15-fold increase in NO3RR activity and 200-mV improvement in overpotential for the 3D CoPB-C8 box structure compared to its 2D CoTPP counterpart. Synthetic tuning of peripheral alkyl substituents highlights the importance of supramolecular porosity and cavity size on electrochemical NO3RR activity. These findings establish the incorporation of 2D molecular units into 3D confined space microenvironments as an effective supramolecular design strategy for enhancing electrocatalysis.

Conflict of interest

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available in the supplementary material of this article.

The full text of this article hosted at iucr.org is unavailable due to technical difficulties.