# Trisferrocenyltrithiophosphite-Copper(I) Bromide Composites for Electrochemical CO2 Reduction

## TL;DR

This paper reports on new copper-based composites that efficiently convert CO2 into methanol and ethanol through electrochemical reactions.

## Contribution

The study introduces tunable trisferrocenyltrithiophosphite–copper(I) bromide composites with distinct catalytic products based on Cu-to-ligand ratios.

## Key findings

- The 1:1 composite produced methanol with 5.79% Faradaic efficiency, while the 2:1 composite produced ethanol with 9.26% efficiency.
- The composites showed excellent stability with only a 9% decline in current density over 5 hours of electrolysis.
- Structural integrity was maintained before and after testing, as confirmed by PXRD analysis.

## Abstract

Copper-based catalysts have emerged as promising materials for electrochemical carbon dioxide reduction reactions, owing to copper’s unique ability to facilitate multi-electron transfer processes and produce valuable products such as methanol and ethanol. In this study, novel trisferrocenyltrithiophosphite–copper(I) bromide composites with Cu-to-ligand molar ratios of 1:1 and 2:1 were synthesized and evaluated for their catalytic performance. The composites were characterized by a combination of techniques, including powder X-ray diffraction (PXRD), linear sweep voltammetry (LSV), potentiostatic testing, chromatographic analysis, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements demonstrated significant current enhancements in the presence of CO2, highlighting the composites’ catalytic activity. Potentiostatic tests revealed excellent stability, with only a 9% decline in current density over 5 h of electrolysis. Product analysis via gas chromatography indicated the formation of methanol for the 1:1 composite and ethanol for the 2:1 composite with Faradaic efficiencies of 5.79% and 9.26%, respectively. While absolute efficiencies remain modest due to competitive hydrogen evolution, these results demonstrate a tunable catalytic performance based on the Cu-to-ligand ratio. SEM and XPS studies further supported the formation of active catalytic centers and changes in the oxidation states of copper during CO2 reduction. PXRD analysis confirmed the retention of structural integrity for both composites before and after catalytic testing.