Ni-doped TiO2 hollow spheres as electrocatalysts in water electrolysis for hydrogen and oxygen production

This work represented the electrocatalytic properties of Ni-doped titania hollow sphere materials in hydrogen and oxygen evolution during water electrolysis from acidic media. Titania hollow sphere particles were synthesized using poly(styrene-methacrylic acid) latex as template material, and various amount of nickel were doped over the sphere using nickel (II) sulfate as the precursor of nickel. The presence of rutile TiO2 and NiO phases were revealed during XRD analysis, indicating the critical growth of nickel on the surface of the hollow sphere catalysts. BET surface area results also shown the 166.76 m2 g−1 value for 30 wt% Ni/TiO2 hollow sphere sample. The SEM and TEM images were confirmed the hollow sphere structure of the catalysts with diameter of 0.8–0.9 μm. The cyclic voltammetric studies proved the presence of both hydrogen and oxygen evolution peaks for all the hollow sphere samples. The anodic peak current density value, which usually represents the oxygen evolution phenomenon, was revealed as 13 mA cm−2 for 25 wt% Ni-loaded sample; whereas, the hydrogen evolution peak was most intense for 30 wt% Ni/TiO2 material with cathodic peak current density of 32 mA cm−2. The average value of −1.42 were determined as the reaction order of the system irrespective of the nickel loading and heating duration in the synthesis of hollow sphere materials. During photocatalytic water splitting, 30 wt% Ni/TiO2 hollow sphere sample yielded the highest amount of hydrogen in all irradiation time span.