Tetraammineplatinum(II) and Tetraamminepalladium(II) Chromates as Precursors of Metal Oxide Catalysts

Abstract

Abstract [M(NH 3 ) 4 ]A (M=Pt, Pd; A=CrO 4 , Cr 2 O 7 ) and [Pt(NH 3 ) 4 (NO 2 )(Cr 2 O 7 )]NO 3 complex salts were synthesized and characterized by a number of physicochemical methods of analysis (IR, single‐crystal and powder XRD, and simultaneous thermogravimetry and differential scanning calorimetry with evolved gas analysis mass spectrometry). Thermolysis of the salts obtained in a hydrogen atmosphere proceeds with the partial reduction of chromium to a metallic state and the formation of M x Cr 1− x (M=Pt, Pd) metal solid solution with a chromium content of up to 22 at % and chromium(III) oxide. The thermal decomposition of salts in an inert and oxidizing atmosphere passes through the formation stage of the MCrO 2 phase with the delafossite structure followed by its subsequent decomposition into chromium(III) oxide and noble metal. Nanosized Pt−Cr 2 O 3 and Pd−Cr 2 O 3 composites obtained by the thermolysis of precursor salts in air at 500 °C and being held at this temperature for 1 h showed a high catalytic activity in the CO total oxidation (TOX) and preferential oxidation in the excess of hydrogen (PROX) processes compared with that of monometallic Pt and Pd powders.