Sphere-like PdNi Alloy: Unveiling the Twin Functional Properties toward Oxygen Reduction and Temperature-Dependent Methanol Oxidation for Alkaline Direct Methanol Fuel Cells

Abstract

The development of high-performance bifunctional palladium-based (Pd) alloys for the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) is a great challenge in direct methanol fuel cells. The incorporation of an oxophilic atom into the Pd atom is an effective strategy to enhance the electrocatalytic activity of the catalysts. Herein a sphere-like PdNi alloy (sPdNiA) was developed via a simple hydrazineassisted reduction method to overcome the kinetic drawbacks of palladium and delivers superior ORR/MOR performance. The successful alloy formation, the induced strain effect in the electronic structure, and structural characteristics of the sPdNiA were confirmed through XRD, XPS, and HR-TEM studies. As a result, for ORR, the sPdNiA exhibits a positive halfwave potential (E 1/2 ) of ∼0.854 V (vs RHE) compared to the pure Pd (0.833 V vs RHE) nanoparticles. For MOR, the sPdNiA presents the low onset potential and high mass activity of 518 mA mg Pd −1 in 1.0 M KOH electrolyte. Furthermore, the temperature-dependent MOR and 3D Bode plot investigations reveal a five-fold higher mass activity at elevated temperature (60 °C) with a lower activation energy (E a ). For the first time, the direct methanol fuel cell is fabricated utilizing sPdNiA as a bifunctional electrode, exhibited a higher peak power density (P max ) of 34 mW cm −2 , whereas 22 mW cm −2 was obtained for Pd Np-based fuel cells. Incorporating oxophilic atom (Ni) not only improves the performance of Pd but significantly reduces the cost of the catalyst material by lowering the Pd content.

Synthesis of MnOOH and its application in a supporting hexagonal Pd/C catalyst for the oxygen reduction reaction

“…The five strong diffraction peaks on the XRD spectrum of MnOOH correspond to the crystal plane diffraction peaks (111), (020), (002), (220), and (311), indicating that MnOOH has a polycrystalline structure. 42,43 When the total area of MnOOH diffraction peaks is fitted to the area of the amorphous region, the crystallinity of MnOOH is calculated to be 81.5%, indicating that MnOOH crystals have large particles and good crystallinity. For MnO 2 -2 and MnO 2 -3, it can be seen from the diffraction peaks of the XRD pattern that their diffraction peak intensity is relatively low, there are many miscellaneous peaks, their crystallinity is not good, and their accurate configuration cannot be determined by standard cards.…”

“…It can be inferred that the catalyst has a face-centered cubic structure. 44–46 As shown in Fig. 2d, the XRD spectra of MnO 2 -1 (MnOOH) and 20%Pd-C-MnOOH-1 : 1 were placed on the same scale.…”

“…Because of the addition of sucrose to the 20%Pd-C-MnOOH-1 : 1 catalyst during the synthesis process, carbon spheres were generated after reduction. 46 Therefore, the XPS spectra of C were also analyzed. As shown in Fig.…”

Enhanced Metal–Support Interfacial Interaction of Pd@FeNi-CoO Composites for Efficient Nitrate Reduction to Ammonia

“…Activated *H is often considered to be the key to increased capacity and reduced energy consumption. − Palladium (Pd)-based catalysts with high hydrogen evolution reaction (HER) activity typically exhibit low overpotential and significant NO 3 RR activity. − Transition metals (such as Fe, Co, and Ni) are inexpensive and their d-orbitals are in an unfilled state, making them susceptible to electron transfer. Their introduction can not only reduce the amount of Pd to achieve cost savings but also regulate the electron structure between different elements to promote the catalytic performance of NO 3 RR. − Besides, constructing a metal–support interface can form an enhanced metal–support interaction, which can improve the catalytic activity and significantly enhance the catalytic stability. − Therefore, there is still much room for progress in designing Pd-based catalysts with enhanced metal–support interfacial interaction for efficient and stable NO 3 RR.…”

Synergism of CoO–Ni(OH)2 nanosheets and MOF-derived CNTs array for methanol electrolysis

“…The methanol electrooxidation system has been widely studied in recent years. Similar to the OER process, the noble-metal-based materials, such as Pt, 21 Pd, 22 and Ru, 18 exhibit excellent MOR performance; however, their applications are hindered by high costs and poor resistance to CO poisoning during the catalytic reaction. 17,23 In addition, they are more prone to completely oxidizing methanol to greenhouse and low-value gases.…”