Electronic Structure Engineering of Pt-Ni Alloy NPs by Coupling of Gold Single Atoms on N-Doped Carbon for Highly Efficient Oxygen Reduction Reaction and Hydrogen Evolution Reaction.

Improving the catalytic activity and durability of platinum-based alloy catalysts remains a formidable challenge in the context of renewable energy electrolysis applications. Herein, a facile and rapid photochemical deposition strategy for the synthesis of gold single atoms (Au SAs) anchored on N-doped carbon is presented. These Au SAs serve as a charge redistribution support for Pt-Ni alloy nanoparticles (PtNiNPs/AuSA-NDC), creating an extended electron-donating interface with Pt-Ni alloy sites. Consequently, the PtNiNPs/AuSA-NDC hybrid catalyst manifests exceptional catalytic performance and durability in both the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) under acidic conditions. Specifically, in ORR, it exhibits a half-wave potential (0.92 V vs RHE), with a mass activity 20.4 times superior to Pt/C at 0.9 V. In HER, PtNiNPs/AuSA-NDC demonstrates a notably reduced overpotential of 19.1 mV vs RHE at 10 mA cm-2 and a mass activity 38 times higher than Pt/C (at 0.25 mV). Furthermore, this hybrid catalyst displays outstanding durability, with only an 8.0 mV decay observed for ORR and a 6.9 mV decay for HER after 10 000 cycles. Theoretical calculations provide insight into the mechanism, demonstrating that isolated Au sites effectively modulate the electronic structure of Pt-Ni alloy sites, facilitating intermediate adsorption and enhancing reaction kinetics.

Synergistic effect of Pt-Ni dual single-atoms and alloy nanoparticles as a high-efficiency electrocatalyst to minimize Pt utilization at cathode in polymer electrolyte membrane fuel cells.

Pt-Ni (111) alloy nanoparticles (NPs) and atomically dispersed Pt have been shown to be the most effective catalysts for oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs) as well as less expensive compared to pure Pt NPs. To meet reaction kinetic demands and minimize the Pt utilization at cathode in PEMFCs, we propose a novel electrocatalyst composed of dual single-atoms (Pt, Ni) and Pt-Ni alloy NPs dispersed on the surface of N-doped carbon (NDC); collectively, PtNiSA-NPS-NDC. The optimized PtNiSA-NPS-NDC catalyst displays excellent mass activity and durability compared to commercial Pt/C. Electrocatalytic measurements show that the PtNiSA-NPS-NDC catalyst, with a metal loading of 4.5 wt%, exhibited distinguished ORR performance (E1/2 = 0.912 V) through a 4-electron (4e-) pathway, which is higher than that of commercial 20 wt% Pt/C (E1/2 = 0.857 V). The DFT simulations indicate Pt-Ni alloy NPs and PtNiN2C4 atomic structure are the mobile active sites for ORR catalytic activity in PtNiSA-NPS-NDC. As a cathode catalyst in PEMFC, the Pt utilization efficiency in the PtNiSA-NPS-NDC catalyst is 0.033 gPt kW-1, which is 5.6 times higher than that of commercial Pt/C (0.185gPt kW-1). Therefore, the consumption of precious metals is effectively minimized.

Dissimilar Materials Welding with a Standoff-Free Vaporizing Foil Actuator between TRIP 1180 Steel Sheets and AA5052 Alloy.

This paper mainly demonstrates an advanced type of the vaporizing foil actuator welding (VFAW) process between GPa-grade steel (TRIP1180) and aluminum alloy (AA5052-H32) without applying standoff. To secure a flying distance during the VFAW process, the preformed target sheet shaped like a circular indentation has been utilized. It is necessary to optimize process parameters integrated with geometrical design of the preform since the welding strength can be decreased beyond the optimum input energy in the standoff-free VFAW process. The welded surface was evaluated by SEM-EDS, XRD, EBDS, and TEM to analyze the welding mechanism and composition at the welding interface. The diffusion zone including the AlFe3 phase was observed at the welded interface which has high grain density due to the high-speed impact by increasing the welding strength, which leads to the perfect welding between the dissimilar materials.