Effect of reduction method on the surface states of Pt/Al₂O₃

Pt/Al₂O₃ with Pt loading of 5% was prepared and characterized by infrared spectroscopy (IR) combined with CO chemisorption, energy dispersive spectrometry (EDS), and transmission electron microscopy (TEM). The effects of reduction methods including commonly used dry reduction by gaseous H2 and wet reduction by sodium formate (HCOONa) aqueous solution on the surface states of Pt/Al₂O₃ were investigated. The results show that both the calcination and reduction can affect the particle sizes and surface sites of Pt. For the catalyst Pt/Al₂O₃ reduced by HCOONa solution, the ratio of terrace to step sites on the surface of Pt increases along with the calcination temperature. Subsequent to the identical calcination procedures, the wet reduction by HCOONa solution results in less residual chlorine and lower Pt dispersion than the dry reduction by gaseous H₂. The violent reduction condition of HCOONa solution and the presence of water are both responsible for the agglomeration of Pt particles. The presence of water can facilitate the dissolution and removal of chlorine from the catalysts when reduced in an aqueous solution.