Combining High Porosity with High Surface Area in Flexible Interconnected Nanowire Meshes for Hydrogen Generation and Beyond

Abstract

Nanostructured metals with large surface area have a great potential for multiple device applications. Although various metal architectures based on metal nanoligaments and nanowires are well known, they typically show a tradeoff between mechanical robustness, high surface area and high (macro)porosity, which, when combined, could significantly improve the performance of devices such as batteries, electrolyzers or sensors. In this work we rationally designed templated networks of interconnected metal nanowires, combining for the first time high porosity of metal foams, narrowly-distributed macropores and a very high surface area of nanoporous dealloyed metals. Thanks to their structural uniformity, the few-micron thick nanowire meshes are also remarkably flexible and durable. We show how the textural properties of the material can be precisely tuned to optimize the nanowire networks for applications in different devices. In an exemplary application in electrolytic production of hydrogen, thanks to its high surface area, a few-micron thick nanomesh outperformed a 300 times thicker nickel foam. Furthermore, thanks to its high porosity, the Pt-doped nanomesh surpassed a microporous Pt/C cloth, demonstrating benefits of the optimally designed nanowire structure for a simultaneous improvement and miniaturization of electrochemical devices. This work extends the potential of interconnected nanowires to multiple new research and industrial applications requiring highly porous and flexible conductive materials with high surface-to-volume ratio. Porosity (%) 60 -80 97 -99+ dpore (nm) c 5 -40 10 -100 Robustness brittle brittle a Data based on Refs. 14,15 . b VSA conversion is presented in Supporting Information. c dpore -effective pore diameter.Various recent studies have shown that rather than having very high surface area but low porosity and small pores, an optimal, mechanically stable current collector should exhibit a balanced combination of high surface area and high porosity, together with sufficiently large, interconnected and preferably ordered pores, whose optimal size depends on the particular application. [16][17][18][19] Currently, however, even the state-of-the-art porous metals, such as dealloyed metals *

Electrochemical Determination of Porosity and Surface Area of Thin Films of Interconnected Nickel Nanowires

“…The detailed fabrication of the nickel nanomesh is reported in our previous work. 11 Briefly, the nickel nanomesh was electrodeposited inside the 3D-porous anodic aluminum The cross-validation of the nanomesh surface area was done by Kr adsorption at 77 K and applying the BET method in the 0.003-0.005 p/p 0 range, according to the previously described methodology. 48 Prior to the measurement, the samples were degassed in vacuo at 110 o C for 12 h. Five nanomesh samples (each having 3.3 µm-thick network and nanomesh footprint area of 2.54 cm 2 ) were measured simultaneously to be above the detection limit (0.1 m 2 ).…”

“…In our recent work, we reported fabrication and electrolytic applications of porous interconnected nickel nanowire meshes. 11 The material can be made from 3D-porous anodic aluminum oxide (AAO) templatesa less-known class of AAO templates with both horizontal and vertical pores, made by anodizing aluminum alloys. [12][13][14] The templated interconnected nanowire materials had also been described a number of previous times, with the applications ranging from batteries 7,15 and photonics 16 to water condensation.…”

A High‐Surface‐Area Carbon‐Coated 3D Nickel Nanomesh for Li–O2 Batteries

“…Related to this last topic, the rechargeability of the Li-O 2 battery is hindered by the formationo ft he insulator Li 2 O 2 , [3] typically formed during discharge by reaction of Li + ions with O 2 radicals. [10] Here, the 3 mm thick Ni nanomeshi se quivalent to a0 .7 mmt hick planarN ia ccording to Faraday's law with 76 %p orosity.D espite these advantageousa spects, Ni itself could promote an alternative conversion reaction [11] andd etrimentals ide reactions such as electrolyted egradation,w hich disqualifies pure Ni as ab inder-free electrode for Li-O 2 batteries. Li + /Li)i sa pplied, which may bring additional parasitic reactions (e.g.,electrolyte decomposition).…”

“…This AAO porousf ilm could be convertedi nto highly ordered 3D Ni nanomesh, the structure of whichw as determined by the primitive AAO template, followed by Ni plating and AAO etching. [10] Here, the 3 mm thick Ni nanomeshi se quivalent to a0 .7 mmt hick planarN ia ccording to Faraday's law with 76 %p orosity.D espite these advantageousa spects, Ni itself could promote an alternative conversion reaction [11] andd etrimentals ide reactions such as electrolyted egradation,w hich disqualifies pure Ni as ab inder-free electrode for Li-O 2 batteries. There is the possibility of fabricating am uch thicker version, depending on the initial thickness of the aluminum alloy layer (Figure 1b).…”

“…There is the possibility of fabricating am uch thicker version, depending on the initial thickness of the aluminum alloy layer (Figure 1b). [10] Here, the 3 mm thick Ni nanomeshi se quivalent to a0 .7 mmt hick planarN ia ccording to Faraday's law with 76 %p orosity.D espite these advantageousa spects, Ni itself could promote an alternative conversion reaction [11] andd etrimentals ide reactions such as electrolyted egradation,w hich disqualifies pure Ni as ab inder-free electrode for Li-O 2 batteries. [8] Therefore, it is of great impor- tance to find as uitable material that could be deposited electrochemically or through other non-destructive deposition techniques, such as chemical vapor deposition (CVD), on the 3D Ni nanomeshsubstrate.…”