PtO x Cl y (OH) z (H 2 O) n Complexes under Oxidative and Reductive Conditions: Impact of the Level of Theory on Thermodynamic Stabilities.

Platinum-based catalysts with Cl - , OH - , O 2- and H 2 O ligands, are involved in many industrial processes. Their final chemical properties are impacted by calcination and reduction applied during the preparation and activation steps. We investigate their stability under these reactive conditions with density functional theory (DFT). We benchmark various functionals (PBE-dDsC, optPBE, B3LYP, HSE06, PBE0, TPSS, RTPSS and SCAN) against ACFDT-RPA. PBE-dDsC is well adapted, although hybrid functionals are more accurate for redox reactions. Thermodynamic phase diagrams are determined by computing the chemical potential of the species as a function of temperature and partial pressures of H 2 O, HCl, O 2 and H 2 . The stability and nature of the Pt species are highly sensitive to the activation conditions. Under O 2 , high temperatures favour PtO 2 while under H 2 , platinum is easily reduced to Pt(0). Chlorine modifies the coordination sphere of platinum during calcination by stabilizing PtCl 4 and shifts the reduction of platinum to higher temperatures under H 2 .