Paragenesis of Palladium–Cobalt Nanoparticle in Nitrogen‐Rich Carbon Nanotubes as a Bifunctional Electrocatalyst for Hydrogen‐Evolution Reaction and Oxygen‐Reduction Reaction

Abstract

The hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR) play important roles in many energy conversion and storage systems. To accelerate the reaction processes, there is a constant need for efficient new catalysts. In the present work, we have developed a facile pyrolysis-based process for the co-synthesis of palladium-cobalt nanoparticles supported on carbon nanotubes (Pd-CoCNTs), which exhibit superior catalytic activity for the HER and enhanced ORR performance. Non-agglomerated Pd nanoparticles of diameters 2-4 nm are uniformly distributed on the surface of CoCNTs, while the inner Co particles are an essential element in forming the framework of the CoCNTs. Compared to the Pd-free N-rich CoCNTs, Pd-CoCNTs have a more defective surface with a larger electrochemically active surface area (ECSA), and show enhanced ORR activity, outstanding methanol tolerance, and long-term stability in alkaline solution. At a low Pd loading of 0.0292 mg cm , the Pd-CoCNTs require overpotentials of 0.024 V and 0.215 V to catalyze the HER and to drive a current density of 50 mA cm in acidic solution, respectively. The palladium nanoparticles on the surface of the CoCNTs are considered to be highly active sites for HER, based on the results of control experiments, and it is easy to adjust the catalytic activity of the Pd-CoCNTs by changing the concentration of Pd therein. The proposed method provides a means of fabricating efficient bifunctional catalysts with controllable low contents of precious metals.

Highly Crystalline Pd13Cu3S7 Nanoplates Prepared via Partial Cation Exchange of Cu1.81S Templates as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction

“…42 However, Pd alone is seldom considered as a great catalyst for HER. 43,44 In our study, according to the surface structure of Pd 13 Cu 3 S 7 NPs, a surface atomic portion of Pd in the nanostructure is about 65%, which is comparable to the optimum Pd coverage for the HER demonstrated in the previous work. 42 Tafel slope analysis implies that Pd 13 Cu 3 S 7 NPs/C follows a Volmer−Heyrovsky pathway, 45 which is fast hydrogen adsorption (Volmer reaction) and slow discharge reaction by the combination between adsorbed hydrogen and a proton (Heyrovsky reaction).…”

Facile Synthesis of Polyhedral Pd Nanocrystals as a Highly Active and Methanol-Tolerant Electrocatalyst for Oxygen Reduction

“…The coexistence of different valences of Pd in polyhedral Pd/XC‐72 catalyst can be found in the XPS patterns (see Figure B ). By using a Gaussian fitting method, the intense doublet peaks at 334.5 and 339.8 eV, respectively are assigned to metallic Pd 0 and the other two peaks at 335.4 and 340.6 eV are ascribed to Pd 2+ species ,. Furthermore, the relative peak area of Pd 0 in polyhedral Pd crystals is about 70.3% of the total by measuring the relative peaks.…”

MOF-Derived Isolated Fe Atoms Implanted in N-Doped 3D Hierarchical Carbon as an Efficient ORR Electrocatalyst in Both Alkaline and Acidic Media

“…Because of its sluggish kinetics, the cathodic oxygen reduction reaction (ORR) is a great challenge limiting the development of advanced energy conversion technologies, including fuel cells and metal–air batteries. − Materials based on platinum group metals (PGMs) have been demonstrated to be the most effective catalysts for ORR so far; however, the concerns related to their scarcity, high cost, and low stability are the huge obstacles for their practical application. , In this context, some carbon-based composites (M–N–C) consisting of transition metals (M = Fe, Co, Ni, etc.) and nitrogen, especially Fe–N–C, have been emerging as the most promising candidates to substitute PGM catalysts by virtue of their low cost, high activity, and stability. − Numerous published results have disclosed that the Fe–N x (nitrogen-coordinated iron sites, x refers to the coordination number) moieties confined within a carbon framework are the critical active sites for ORR. ,− Downsizing the Fe–N x architectures to the atomic level can optimize the utilization of metal sites and thereby increase the density of active sites.…”