# Sn-Decorated Cu/Cu2O Electrodes Enable Selective CO2 Reduction to Formic Acid under Realistic Flue Gas Streams

## TL;DR

This paper shows that Sn-decorated Cu/Cu2O electrodes can efficiently convert CO2 into formic acid even in complex flue gas mixtures.

## Contribution

The study introduces a scalable method to create Sn-decorated Cu/Cu2O electrodes for selective CO2 reduction in realistic gas conditions.

## Key findings

- Sn-decorated electrodes achieved 80% Faradaic efficiency and 370 μmol cm–2 h–1 production rate under pure CO2.
- High selectivity (90% Faradaic efficiency) was maintained in simulated flue gas despite lower CO2 partial pressure.
- Flue gas exposure caused electrode restructuring, including surface roughening and carbonate formation.

## Abstract

The electrochemical reduction of CO2 is typically
investigated
under pure CO2 feeds, but practical deployment must address
more complex and dilute sources such as flue gases. Here, we studied
Cu/Cu2O electrodes decorated with tin (Sn) synthesized
using a scalable electrodeposition method and post-treatments under
both pure CO2 and reactive nitrogen oxide-containing simulated
flue gas, toward formic acid synthesis. Raman spectroscopy and Atomic
Force Microscopy analyses revealed that flue gas exposure induces
heterogeneous restructuring of the electrode with surface roughening,
surface carbonate formation, and localized redeposition processes.
Optimal catalyst performance under pure CO2 was achieved
with intermediate Sn coverage of 3 min electrodeposition, delivering
Faradaic efficiencies of 80% and production rates of 370 μmol
cm–2 h–1. Sn-modified Cu2O electrodes also exhibited high selectivity toward formic acid under
acidic gas containing simulated flue gas, reaching Faradaic efficiencies
of 90% albeit at production rates of 113 μmol cm–2 h–1, despite a 10-fold reduced CO2 partial
pressure. These results demonstrate that interfacial Sn–Cu
structures enabled selective CO2RR even under challenging
feed conditions, pointing out both the opportunities and limitations
of translating laboratory-scale catalysts to realistic gas streams.