Mechanism of Phosphorus and Chlorine Passivating a Nickel Catalyst: A Density Functional Theory Study

Methane chloride (CH3Cl) in syngas is able to suppress the phosphine (PH3) poisoning effects on a solid oxide fuel cell under various conditions. The mechanism is revealed by combining a thermodynamic analysis and a study of P-Cl chemisorption at nickel surface. The resulting negative Gibbs energy is favorable to reactions between gaseous phosphorus (considered to be P2) and CH3Cl, predicting the generation of phosphorus trichloride (PCl3). However, the binding energies between P/Cl and nickel show that the PCl3 formed is not stable, so chlorine combined with P under these conditions at nickel surface is therefore expected to inhibit passivation by phosphorus.