Ethylene Hydrogenation on a Platinum Nanocoating at Various Electric Potentials

Resumo

The possibility of controlling the rate of ethylene hydrogenation on a platinum nanocoating is established by applying to it electric potentials of different polarities and magnitudes from an external voltage source. At a negative potential of −10 V, the hydrogenation rate increases by 4%, whereas at a positive potential of +10 V, the hydrogenation rate increases by 42% under the conditions of the experiment at room temperature, atmospheric pressure, and an initial mixture composition of 0.09C₂H₄ + 0.91H₂. Quantum-chemical calculations of the energy of the reaction of platinum hydride with hydrogen, Pt₂H₂ + H₂ → Pt₂H₃ + H, and the energy characteristics of similar reactions involving negatively and positively charged Pt₂H₂ are performed. It has been demonstrated that the presence of a negative or positive charge on Pt₂H₂ lowers the endothermicity of formation of H radicals by 18.4 or 22.5 kcal/mol, respectively. Based on the calculation results, a mechanism is proposed to explain the effect of the charge of a platinum coating on its catalytic activity in ethylene hydrogenation.