Nitric acid

The Ti_0.8Sn_0.2O₂-C composite supports were prepared using Black Pearls 2000 active carbon (Cabot Corporation, Boston, MA, USA). For the composite synthesis, titanium isopropoxide (Sigma-Aldrich, St. Louis, MO, USA, 97%), tin (IV) chloride-5-hydrate (Honeywell Riedel-de Haën GmbH, Seelze, Niedersachsen Germany, 98%), nitric acid (65%, a.r., Molar Chemicals, Halásztelek, Hungary) and ultrapure water (18 MΩ cm, produced by Millipore equipment, (Burlington, MA, USA)) were used. The Pt precursor for electrocatalyst synthesis was H₂PtCl₆·6H₂O (Sigma-Aldrich, St. Louis, MO, USA, 37.5% Pt). Further chemicals used for the Pt loading were ethanol (99.55%), ethylene glycol (99.8%), HCl (37%) and NaBH₄ (99.95%) (all obtained from Molar Chemicals). The catalyst ink for the electrochemical studies was prepared using a Nafion solution (DuPont™ Nafion^® PFSA Polymer Dispersions DE 520, The Chemours Company, Wilmington, DE, USA), isopropanol (Molar Chemicals) and ultrapure water (see above).

Titania nanoparticles were synthesized using titanium-isopropoxide (≥97.0%% Sigma Aldrich Inc., St. Louis, MO, USA) Citric acid (ACS reagent, ≥99.5%) for gel formation was obtained from Sigma Aldrich Inc. Pt(NH₃)₄(NO₃)₂ (≥50.0% Pt basis, Sigma-Aldrich Inc.) was the precursor of supported Pt nanoparticles. Other chemicals included methanol (a.r., 99.996%, Molar Chemicals Ltd., Budapest, Hungary), absolute ethanol (100.0%, AnalaR NORMAPUR, VWR International, Fontenay-sous-Bois, France) and hydrochloric acid (36,4%, AnalaR NORMAPUR, VWR), hydrofluoric acid (38 41%, a.r., Reanal, Budapest, Hungary) and nitric acid (65 w%, a.r., Molar Chemicals Ltd.). Double distilled water (18 MΩ) was used for the synthesis of photocatalysts and for the preparation of methanol solution. The gases (H₂, N_2, Ar) used in this work were products of Linde Gáz Magyarország Zrt. (Budapest, Hungary) with 5.0 purity. Special mixture of 5% H₂ in N₂ for calibration of the gas chromatograph was bought from Messer Hungarogáz Ltd. (Budapest, Hungary).

Titanium–isopropoxide (Ti(O-i-Pr)₄, Sigma-Aldrich, St. Louis, MO, USA, 97%), ammonium heptamolybdate tetrahydrate ((NH₄)₆Mo₇O₂₄ × 4H₂O, Merck Darmstadt, Germany, 99%), and hexachloroplatinic acid hexahydrate (H₂PtCl₆ × 6H₂O, Sigma-Aldrich, St. Louis, MO, USA, 37.5% Pt) were used as Ti, Mo, and Pt precursor compounds, respectively. A 5% Nafion^® dispersion (DuPont™ Nafion^® PFSA Polymer Dispersions DE 520, The Chemours Company, Wilmington, DE, USA) was used for catalyst ink preparation. Other chemicals included nitric acid (HNO₃, 65%, a.r.), ethanol (99.55%), 2-propanol (i-C₃H₅OH, 99.9 V/V%, a.r), ethylene–glycol (EG, 99.8%), sodium borohydride (NaBH₄, 99.95%) (all from Molar Chemicals, Halásztelek, Hungary). Glucose (Reanal, Budapest, Hungary, a lt.), sodium hydroxide (NaOH, Reanal, Budapest, Hungary > 98%), and sulfuric acid (H₂SO₄, Merck, Darmstadt, Germany, 96% p.a). BP and V carbons (both from Cabot, Boston, MA, USA) were used as starting carbonaceous materials. F-BP carbon was prepared as we described before [47 (link)]. Briefly, BP previously pre-treated in nitrogen (5.0 purity, Linde Gáz Magyarország Zrt, Répcelak, Hungary) at 1000 °C was modified using a two-step treatment with HNO₃ and Glucose. Commercial 20 wt.% Pt on V support (Pt/C, C-20-Pt from QuinTech, Göppingen, Germany) was used as a reference electrocatalyst.