Catalyst Composites of Palladium and N-Doped Carbon Quantum Dots-Decorated Silica and Reduced Graphene Oxide for Enhancement of Direct Formic Acid Fuel Cells

Abstract

Pd-based catalysts consisting of Pd nanoparticles on nitrogen-doped carbon quantum dots (N-CQDs) modified silica (SiO 2 ) and reduced graphene oxide have been synthesized through reduction for use as catalysts for improved formic acid oxidation. The structure, morphology, chemical composition, functional groups, and porosity of the synthesized catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and Brunauer–Emmett–Teller (BET) spectroscopy, respectively. Their electrocatalytic activities were also evaluated by electrochemical measurements. The differences in the average particle sizes found for Pd/N-CQDs-SiO 2 -rGO, Pd/N-CQDs-rGO, and Pd/rGO were 4.81, 5.56, and 6.31 nm, respectively. It was also found that the Pd/ x N-CQDs-SiO 2 - y rGO composite catalysts (where x and y is 1 to 4) can significantly improve the activity and stability toward formic acid electrooxidation compared with Pd/rGO and commercial Pt/C. The mass activities of Pd/N-CQDs-SiO 2 -rGO, Pd/N-CQDs-rGO, and Pd/rGO were 951.4, 607.8, and 157.6 mA g –1 , respectively, which was ca. 6–7 times compared with Pd/rGO and approximately 3–4 times compared with commercial Pt/C. With low potential for CO oxidation and high current intensity, the composites of rGO, SiO 2 , and N-CQDs into Pd-based catalysts improved the catalytic activity of the prepared catalyst for the oxidation of formic acid in acidic media. The value of the Tafel slope designated that the chief path of the prepared catalysts is the dehydrogenation process. These prepared catalysts exhibit promise toward the development of high-performance Pd-based electrocatalysts for formic acid oxidation.

PdNiONF−Borophene Nanocomposite as a Promising Catalyst for Ethanol Electro‐Oxidation Reaction

“…Figure 1 (A) and (B) illustrate the XRD patterns of C and Pd/C (commercial) catalysts, respectively. The (100), (002), and (002) planes of carbon black are ascribed to the large peak observed at ~2Ɵ: 10°, 29°, and 41° [14,15] (Figure 1 (A) ). The ~2Ɵ: (100), (002), (111), and (220) observed in Figure 1 (B) corresponds to the plane of the face‐centered cubic structure of Pd as compared to the results from the literature [16–18] .…”

“…The peak positions indicate the types of carbon structures present in borophene, Pd/B, and PdNiONF/B by the display of multiple Raman peaks corresponding to radial breathing modes (RBMs). [15] The RBMs typically appear as sharp peaks in the low wavenumber region (< 300 cm À 1 ), and the presence of RBMs indicates the presence of a cylindrical nanostructure composed of graphitic rolled-up sheets. [46] This possesses an exceptionally high surface area, providing active sites for catalytic reactions.…”

Pronounced effect of yttrium oxide on the activity of Pd/rGO electrocatalyst for formic acid oxidation reaction

“…† The peaks for Pd–O/HO–C O, O C, C–O and HO–C appears at binding energy values of ∼531.3, 532.2, 534.6, and 533.7 eV respectively. 44 …”

“…The diffraction peak for yttrium was not observed in the PXRD pattern of Pd y Y x /rGO indicating the amorphous nature of yttrium. 41,42 Reference catalysts PXRD pattern is shown in 44 The pre and post XPS prole of Pd 3d represents the appearance of two distinct peaks at 335.5 eV and 341.0 (Fig. 1e).…”

Carbon Quantum Dot Electrocatalysts in Hydrogen Evolution Reaction

“…CQDs can serve as versatile electrocatalysts, facilitating a wide array of organic transformations, from the reduction and oxidation of organic compounds to the electrochemical synthesis of pharmaceuticals, [ 105 ] complex organic molecules, and valuable chemicals like formic acid. [ 106 ] Additionally, their utility extends to electrochemical sensing, energy storage, and even sustainable approaches to carbon–carbon bond formation. With their versatility and efficacy in driving electrochemical reactions, CQDs hold substantial promise for advancing green and efficient methods in organic electrosynthesis, potentially revolutionizing how we approach organic molecule synthesis and electrochemical applications.…”