Carbon nanotube-supported Pt-Co bimetallic catalysts for preferential oxidation of CO in a H2-rich stream with CO2 and H2O vapor

Carbon nanotube-supported Pt-Co bimetallic catalysts (Pt-Co/CNTs) are prepared for preferential oxidation of CO in a H2-rich stream. The results indicate that the addition of Co into the Pt/CNT catalyst significantly improves catalytic performance, making it superior to other carriers supporting the same composition of Pt–Co. Optimized bimetallic Pt-Co/CNT catalyst can preferentially oxidize dilute CO in a H2-rich stream at a wide temperature window of 313–433 K. At a temperature of 353 K and a H2-rich stream with 1% CO, 0.7–0.8% O2, 20% H2O, 25% CO2 and 50% H2 balanced with N2, this catalyst can afford 100% CO conversion with 62–71% O2 selectivity for over 100 h. The transmission electron microscopic images reveal that the metal nanoparticles are uniformly dispersed on the surfaces of CNTs with an average size of approximately 2–3 nm, independent of Co loading. The results of X-ray photoelectron spectroscopy and nanoscale elemental mapping indicate that most of Co species are in the form of CoO, presenting on the Pt domain. Higher performance of the Pt-Co/CNT is attributed to the interactions between the Pt nanoparticles and CoO, those are supported on CNT surfaces.

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► Addition of proper amount of Co into Pt/CNT improves the dispersion of Pt nanoparticles.
► Most of Co species are in the form of CoO, presenting on the periphery and surface of Pt domain.
► A catalyst of 4.0% Pt-0.7% Co/CNT can completely remove CO in a H2-rich stream at temperatures window of 313–433 K.
► Hydrogen purification can be performed in a feed gas containing 25% CO2 and 20% H2O vapor.