# Tailoring Reconstruction of Co/Cu Mixed Oxide-Derived Tandem Electrocatalysts via In Situ Electrochemical Dissolution–Redeposition for Enhanced Nitrate-to-Ammonia Conversion

## TL;DR

Scientists improved a catalyst for converting nitrate to ammonia by using electrochemical methods to enhance its performance and stability.

## Contribution

A tandem Co3O4/Cu_xO electrocatalyst was developed with enhanced ammonia production through in situ electrochemical reconstruction.

## Key findings

- CA-reconstructed electrocatalyst showed higher faradaic efficiency for ammonia production.
- Electrochemical protocols induced morphological and compositional changes improving performance.
- In situ techniques identified active sites and intermediates in nitrate-to-ammonia conversion.

## Abstract

Cobalt- and copper-based
oxides have emerged as cost-effective
electrocatalysts for the electrochemical nitrate reduction reaction
(NO3RR) to ammonia. However, the cathodic potentials required
for NO3RR induce irreversible structural transformations
that often compromise catalyst stability and selectivity, depending
on the applied electrochemical protocol. To understand the resulting
dynamic structure–performance relationships and improve nitrate-to-ammonia
conversion, a tandem Co3O4/Cu
x
O electrocatalyst was prepared by electrodeposition followed
by thermal treatment, and two surface activation strategies were employed:
by cycles of cyclic voltammetry (CV) or by holding at a constant potential
by chronoamperometry (CA). The CA-reconstructed Co/Cu mixed oxide-derived
electrocatalyst exhibited a higher faradaic efficiency (FE) toward
ammonia across the entire potential window studied (0.00 to −0.40
VRHE). The reconstruction effects induced by both electrochemical
protocols were systematically investigated, revealing morphological,
structural, and compositional changes that underpin the improved nitrate-to-ammonia
conversion. Furthermore, in situ and online electrochemical
techniques were employed to identify intermediates and active sites,
providing new mechanistic insights into the electrochemical nitrate-to-ammonia
conversion pathway. These findings contribute to understanding dynamic
reconstruction phenomena and offer design guidelines for more stable
and selective mixed oxide electrocatalysts for sustainable ammonia
production.