Oxygen Electroreduction Catalyzed by Palladium Nanoparticles Supported on Nitrogen-Doped Graphene Quantum Dots: Impacts of Nitrogen Dopants

• DOI: 10.1021/acssuschemeng.6b01476
• Publication Date: 2016-10-11T22:39:31Z
• Authors: Christopher P. De...; Rene Mercado; Jia En Lu; Vamsi Gadiraju; Mohammad Khan; Shaowei Chen
• Keywords: 02 engineering and technology; 0210 nano-technology

Palladium nanoparticles supported on nitrogen-doped graphene quantum dots (NGQD) were synthesized by hydrothermal coreduction of palladium salts, citric acid, and urea at 160 °C for up to 12 h. Transmission electron microscopic studies showed that in the resulting PdNGQD nanocomposites, small clustered into superstructures 100 nm larger. X-ray photoelectron spectroscopic NGQDs contained only p-type pyridinic pyrrolic nitrogen centers, although total concentrations dopants rather consistent (ca. 10 at. %) among series samples, relative abundance (pyridinic) nitrogens increased (decreased) with prolonging reaction duration, suggesting thermal conversion ones. The binding energy Pd 3d electrons was found increase accordingly, probably due enhanced withdrawing more acidic nitrogens. This suggests apparent interactions between dopants. Consistent results obtained Raman measurements which an D G band intensity ratio, indicative increasingly defective structure NGQD. increasing centers provided structural strains than six-membered heterocycles within graphitic backbone. Electrochemically, PdNGQDs all electrocatalytic activity toward oxygen reduction alkaline media, context onset potential kinetic current density, sample prepared 8 h stand out as best catalyst series, a top specific over eight times better observed when undoped GQDs commercial Pt/C. might be accounted effects manipulated electronic intermediates, compared oxygenated moieties alone GQDs.