TPD TPO TPR

O2 Temperature-Programmed Oxidation (O2 TPO)

Samples were pretreated at 150°C for 2 hours under a helium (He) flow of 30 mL/min to ensure the removal of any physically adsorbed species and to stabilize the sample. Following pretreatment, the temperature was ramped from room temperature (RT) to 800°C at a rate of 10°C/min. An oxidizing gas mixture of 5% O2 in helium (He) was used, with a flow rate set at 50 mL/min. This procedure was designed to oxidize the sample progressively, allowing for the characterization of oxidation behavior over a broad temperature range.

H2 Temperature-Programmed Reduction (H2 TPR)

Samples underwent a similar pretreatment at 150°C for 2 hours, but under an argon (Ar) atmosphere, with a flow rate of 30 mL/min. The temperature was increased from RT to 1000°C at a heating rate of 10°C/min. A reducing atmosphere was created using a gas mixture of 5% hydrogen (H2) in argon (Ar), flowing at 50 mL/min. This method is utilized to analyze the reducibility of the samples, highlighting the temperature-dependent reduction processes.

CO Temperature-Programmed Reduction (CO TPR)

The pretreatment protocol for CO TPR was identical to that for H2 TPR, with samples heated at 150°C for 2 hours under an argon flow of 30 mL/min. Temperature was escalated from RT to 1000°C at a rate of 10°C/min. A reducing gas mixture of 5% carbon monoxide (CO) in argon (Ar) was used, with the flow maintained at 50 mL/min. CO TPR is employed to assess the catalytic sample’s ability to interact with and reduce CO, providing insights into the catalytic properties and potential applications.

 

 

In the study of temperature-programmed techniques to analyze material properties, three distinct procedures were employed: O2 Temperature-Programmed Oxidation (O2 TPO), H2 Temperature-Programmed Reduction (H2 TPR), and CO Temperature-Programmed Desorption (CO TPD).

O2 TPO process begins with pretreatment of the samples at 150°C for 2 hours under a He flow of 30 mL/min to remove any physically adsorbed species and stabilize the samples. After this pretreatment, the temperature of the samples is gradually increased from room temperature to 800°C at a heating rate of 10°C/min and an oxidizing gas mixture consisting of 5% O2 in helium is used, with a flow rate maintained at 50 mL/min. Similarly, for H2 TPR, the samples undergo an initial pretreatment at 150°C for 2 hours under an Ar atmosphere with a flow rate of 30 mL/min. RT to 1000°C at the same rate of 10°C/min using a mixture of 5% H2/Ar, flowing at 50 mL/min. For CO TPD, the approach includes a unique pretreatment step where the samples are exposed to a 5 % CO/He gas mixture at room temperature to facilitate CO adsorption onto the surface of the samples. This is followed by a purging process using helium to eliminate any physically adsorbed CO that is not chemically bound, ensuring that only chemically adsorbed CO is considered during subsequent heating. After purging, the samples are subjected to a temperature ramp under a helium atmosphere, where the temperature is increased from room temperature to 800°C at a heating rate of 10°C/min. The desorption of CO from the sample surfaces is monitored during this ramp. These measurements provide critical insights into potential applications in catalysis.