Dual-site synergistic tandem effect on Pt single-atoms and CeOx nanoclusters for boosted electrocatalytic detection performance of Cr(VI).

Hexavalent chromium (Cr(VI)) is a toxic and carcinogenic pollutant that poses a serious health risk to humans and other living organisms. Single-atom catalysts (SACs) have promising prospects in environmental pollutants (Cr(VI)) detection fields, featuring atomic-level active sites and high atom utilization. However, SACs may face inevitable aggregation during the synthesis or reaction processes. The catalytic efficiency of SACs is limited in complex multi-step reactions due to the simplex active site, which hinders the practical application of SACs. Herein, we confine platinum single atoms (Pt SAs) that are isolated by cerium oxide nanoclusters (CeOx) on reduced graphene oxide (Pt/CeOx/RGO) via controlling the moderately oxidation state (calcination temperature 600 ℃), achieving record-breaking ultralow overpotential (0.279 V) for Cr(VI) electrocatalytic reduction. X-ray absorption fine structure spectra indicate that Pt-O bonds of Pt/CeOx/RGO were stretched after absorbing with Cr(VI), which facilitates strong interaction between Pt SAs with Cr(VI). Pt/CeOx/RGO also exhibits remarkable selectivity for Cr(VI) against common interferents (Hg(II), As(III), Cd(II), Pb(II)) and organic interferents (hydrazine, 2,2'-(Ethylenedioxy) diethanethiol, urea, and hydroquinone). Density functional theory calculations reveal that Pt and CeOx exert a dual-site synergistic tandem effect, which enables Pt SAs and CeOx NCs to achieve efficient catalytic reduction through cooperation and division of reaction sites, significantly lowering the Cr(VI) reduction energy barriers. Herein, the demonstrated tandem catalyst architecture not only advances the frontier of SACs but also opens a promising avenue for developing advanced sensing platforms toward environmental monitoring, remediation, and beyond.