(499e) Structure-Function Relationship of Highly Reactive CuOx Cluster on Co3O4 for Selective Formaldehyde Sensing at Low Temperatures

Designing reactive surface clusters at the nanoscale on metal-oxide supports enables selective molecular in low-temperature catalysis and chemical sensing. However, identifying effective material combinations and reactive sites remains a challenge, but of paramount importance for rational sensor/catalyst design. Here [1], the low-temperature oxidation of formaldehyde with CuO_x clusters on Co₃O₄ is showcased yielding an excellent sensor for this critical pollutant. When deploying flame-aerosol technology in the form of flame spray pyrolysis [2], such CuO_x clusters are finely dispersed on Co₃O₄’s surface, while some Cu²⁺ ions are incorporated into the lattice enhancing thermal stability. Surface-Cu’s speciation is investigated by infrared spectroscopy of adsorbed CO, near-ambient-pressure near edge X-ray absorption fine structure spectroscopy (Cu L₃ edge) temperature-programmed reducibility studies. These identified Cu⁺ and Cu²⁺ species in these CuO_x clusters as active sites. Remarkably, the Cu⁺ surface concentration correlated with the apparent activation energy towards formaldehyde oxidation (Spearman’s coefficient ρ = 0.89) and sensor response (0.96), establishing a connection between kinetics and sensory signals. At optimal composition, such sensors detected down to 3 parts-per-billion (ppb) at moderate temperature of 75 °C, superior to state-of-the-art chemiresistors. Further, selectivity to other aldehydes, ketones, alcohols, and inorganic compounds, as well as robustness to humidity and stable performance over 4 weeks are achieved. These sensors are promising as gas detectors in health monitoring, air and food quality control.

References

[1] D’Andria, M.; Krumeich, F.; Yao, Z.; Wang, F.R. & Güntner, A.T., Adv. Sci. 2024, 11, 2308224.
[2] Güntner, A.T.; Pineau, N. J. & Pratsinis, S.E., Prog. Energ. Combust. Sci. 2022, 90, 100992.