Synergistic Pt–Au Sites on Cu–Ce Oxygen Carriers for Boosting Low-Temperature Chemical Looping CO Preferential Oxidation

Removing trace CO from H2-rich streams is critical for proton exchange membrane fuel cells, and chemical looping preferential oxidation (CL-PROX) offers an intrinsically safe pathway by using lattice oxygen─rather than gas-phase O2─as the oxidant. However, conventional Cu–Ce oxygen carriers are constrained by a trade-off between low-temperature activity and CO selectivity. Here, we demonstrate that bimetallic Pt–Au modification of Cu–Ce oxygen carriers resolves this trade-off through synergistic interactions. A series of PtxAuy/Cu–Ce carriers with systematically varied Pt/Au ratios were synthesized by sol–gel synthesis followed by wet impregnation. The optimal Pt0.33Au0.67/Cu–Ce sample achieved complete CO conversion at 110 °C with ∼80% CO selectivity and maintained stable performance over 30 redox cycles. Integrated TPR, XPS, and HRTEM characterizations revealed that Pt exists predominantly as high-valence Pt4+ species that activate CO, whereas Au is highly dispersed as metallic Au0 species that selectively suppress H2 oxidation. Kinetic analysis gave reduction activation energies of ∼124 kJ·mol–1 (for H2) and ∼13 kJ·mol–1 (for CO), a nearly 10-fold difference that underpins the high CO selectivity. The turnover frequency (TOF) at 110 °C was determined to be 0.266 s–1 (Pt sites) and 0.105 s–1 (Au sites), with Pt outperforming Au by a factor of ∼2.5. This work demonstrates that Pt–Au bimetallic synergy provides an effective strategy for simultaneously enhancing low-temperature activity and selectivity in CL-PROX.