Single Cu Atom Sites on Co3O4 Activate Interfacial Oxygen for Enhanced Reactivity and Selective Gas Sensing at Low Temperature

TL;DR

This study demonstrates that single Cu atom sites on Co3O4 significantly improve low-temperature reactivity and gas sensing capabilities, especially for formaldehyde detection, by activating interfacial oxygen through strong metal-support interactions.

Contribution

It introduces a novel single-atom Cu catalyst on Co3O4 that enhances redox activity and selectivity in gas sensing at low temperatures, surpassing existing nanoparticle-based sensors.

Findings

Single Cu atoms on Co3O4 boost low-temperature oxygen activation.

Cu1-Co3O4 sensors detect formaldehyde down to 5 ppb at 75°C.

Enhanced response exceeds that of CuO nanoparticle catalysts.

Abstract

Controlling the redox landscape of transition metal oxides is central to advancing their reactivity for heterogeneous catalysis or high-performance gas sensing. Here we report single Cu atom sites (1.42 wt%) anchored on Co3O4 nanoparticles (Cu1-Co3O4) that dramatically enhance reactivity and molecular sensing properties of the support at low temperature. The Cu1 are identified by X-ray adsorption near edge structure and feature strong metal-support interaction between Cu2+ and Co3O4, as revealed by X-ray photoelectron spectroscopy. The ability of Cu1 to form interfacial Cu-O-Co linkages strongly reduces the temperature of lattice oxygen activation compared to CuO nanoparticles on Co3O4 (CuONP-Co3O4), as demonstrated by temperature-programmed reduction and desorption analyses. To demonstrate immediate practical impact, we deploy such Cu1-Co3O4 nanoparticles as chemoresistive sensor for formaldehyde vapor that yields more than an order of magnitude higher response than CuONP-Co3O4 and consistently outperforms state-of-the-art sensors. That way, formaldehyde is detected down to 5 parts-per-billion at 50% relative humidity and 75 {\deg}C with excellent selectivity over various critical interferents. These results establish a mechanistic platform for activating redox-active supports using single-atom isolates of non-noble nature that yield drastically enhanced and well-defined reactivity to promote low-temperature oxidation reactions and selective analyte sensing.