Defect-Rich Black Titanium Dioxide Nanosheet-Supported Palladium Nanoparticle Electrocatalyst for Oxygen Reduction and Glycerol Oxidation Reactions in Alkaline Medium
Keerti M. Naik, T. Hamada, Eiji Higuchi, Hiroshi Inoue
Abstract
Direct alcohol fuel cells (DAFCs) play a pivotal role in the synthesis of electrocatalysts with low cost, high catalytic activity, and long durability. Furthermore, platinum catalysts suffer from CO tolerance, which affects their stability. Herein, we report a Mars–van-Krevelen mechanism-based method for preparing hydroxylation-anchoring oxygen-deficient black titanium dioxide nanosheets (B-TiO2–x NSs) via the heating of anatase titanium dioxide nanosheets (TiO2 NSs) with 1-butanol. Spectral analysis of B-TiO2–x NSs demonstrated the existence of oxygen vacancies, Ti3+, and hydroxy groups. Pd nanoparticle (NP)-supported B-TiO2–x NSs (Pd/B-TiO2–x NSs) were prepared by pyrolysis of palladium acetate on the B-TiO2–x NSs and applied as an electrocatalyst for oxygen reduction reaction (ORR) and glycerol oxidation reaction (GOR). For ORR, Pd/B-TiO2–x NSs showed higher catalytic activity due to higher half-wave potential and higher stability due to slower decay in the ORR current in chronoamperometric measurements compared with Pd/C. The improved activity is attributed to the efficient charge transfer or strong metal–support interaction between Ti3+ species and Pd NPs. For GOR, Pd/B-TiO2–x NSs showed higher activity and stability toward GOR compared with Pd/C and selectivity toward fewer carbon atoms. Hence, the Pd/B-TiO2–x NS electrocatalyst opens up developments toward energy conversion devices such as DAFCs.