An in-situ small angle x ray scattering analysis of nanopore formation during thermally induced chemical dealloying of brass thin foils

Abstract

The development of non-noble nano-porous metal materials is hindered by surface oxidation reactions and from the difficulty to generate long range order pore arrays. Dealloying is a promising route to generate such materials by selective chemical etching of metal alloy materials. This process can generate nano-metal materials with superior plasmonic, catalytic and adsorptive surface properties. Here, the impact of properties of the etching solution on the dealloying process to generate nano-pores across thin film alloys was investigated by in-situ SAXS dealloying experiments. Single phase CuZn alloys were used as model materials to evaluate the influence of the solution temperature on the pore formation kinetics. This novel analysis allowed to visualize the change in surface properties of the materials over time, including their surface area as well as their pore and ligament sizes. The dealloying kinetics at the very early stage of the process were found to be critical to both stable pore formation and stabilization. SAXS in-situ data were correlated to the morphological properties of the materials obtained from ex-situ samples by Rutherford back scattering and scanning electron microscopy.

In Situ SAXS Measurement and Molecular Dynamics Simulation of Magnetic Alignment of Hexagonal LLC Nanostructures

“…Small angle X-ray scattering (SAXS) is used in a high-throughput manner for in situ characterization [20] of nanostructures of bulk long range order [21,22,23]. It allows for the determination of alignment and the identification of the self-assembled phases while molecular dynamics (MD) has shown its unique advantages in understanding the structure of membrane and the interfacial affinity [24].…”

Electrochemical Generation of Mesopores and Residual Oxygen for the Enhanced Activity of Silver Electrocatalysts

“…60 Å (small mesopores, from d = 2π/ q ). The generated mesopores were significantly smaller than the macropores produced by the selective etching of metal alloys (up to 5 μm) . As a result, AgO δ with mesopores exhibited an approximately 60-fold higher double-layer capacitance than pristine Ag 2 O 3 (Figure b).…”

“…The generated mesopores were significantly smaller than the macropores produced by the selective etching of metal alloys (up to 5 μm). 39 As a result, AgO δ with mesopores exhibited an approximately 60-fold higher double-layer capacitance than pristine Ag 2 O 3 (Figure 3b). Considering that double-layer capacitance is linearly proportional to ECSA, the generation of mesopores was concluded to strongly increase electrocatalytic activity.…”

“…In general, catalytic activity, expressed in [mol g –1 s –1 ], is proportional to intrinsic catalytic activity, expressed in [mol cm –2 s –1 ], and electrochemically active surface area (ECSA), expressed in [cm 2 g –1 ]. − The practical application of non-Pt catalysts is mainly hindered by their lower (compared to that of Pt-based catalysts) intrinsic activity, which can be increased by alloying and doping. − However, more efficient methods of (i) precise doping level control and (ii) enhancing catalyst utilization efficiency through ECSA maximization are still required. Although selective etching with acids or halogen gas has been employed as a general strategy for carving nanometric voids in carbon, metal carbides, metals, and metal alloys, the electrochemical generation of atomic-scale pores has not been demonstrated, to the best of our knowledge. Because conventional methods used to impregnate porous carbon with metal catalysts often lead to electronic contact loss and Ostwald ripening–induced agglomeration, efficient strategies of preparing electrocatalysts with stable microporous structures and increased intrinsic activity are highly sought after.…”

“…32−36 However, more efficient methods of (i) precise doping level control and (ii) enhancing catalyst utilization efficiency through ECSA maximization are still required. Although selective etching with acids or halogen gas has been employed as a general strategy for carving nanometric voids in carbon, 37 metal carbides, 38 metals, 39 and metal alloys, 40 the electrochemical generation of atomic-scale pores has not been demonstrated, to the best of our knowledge. Because conventional methods used to impregnate porous carbon with metal catalysts often lead to electronic contact loss and Ostwald ripening−induced agglomeration, 41 efficient strategies of preparing electrocatalysts with stable microporous structures and increased intrinsic activity are highly sought after.…”