We fabricate three-dimensional zinc electrodes from emulsion-cast sponges of Zn powder that are thermally treated to produce rugged monoliths. This highly conductive, 3D-wired aperiodic scaffold achieves 740 mA h gZn(-1) when discharged in primary Zn-air cells (>90% of theoretical Zn capacity). We use scanning electron microscopy and X-ray diffraction to monitor the microstructural evolution of a series of Zn sponges when oxidized in Zn-air cells to specific depths-of-discharge (20, 40, 60, 80% DOD) at a technologically relevant rate (C/40; 4-6 mA cm(-2)). The Zn sponges maintain their 3D-monolithic form factor at all DOD. The cell resistance remains low under all test conditions, indicating that an inner core of metallic Zn persists that 3D-electrically wires the electrode, even to deep DOD.
Using a solution-based, non-line-of sight synthesis, we electrolessly deposit ultrathin films of RuO ("nanoskins") on planar and 3D substrates and benchmark their activity and stability for oxygen-evolution reaction (OER) in acid electrolyte under device-relevant conditions. When an electrically contiguous ∼9 nm thick RuO nanoskin is expressed on commercially available, insulating SiO fiber paper, the RuO@SiO electrode exhibits high current density at low overpotential (10 mA cm @ η = 280 mV), courtesy of a catalyst amplified in 3D; however, the mass-normalized activity falls short of that achieved for films deposited on planar, metallic substrates (Ti foil). By wrapping the fibers with a <100 nm thick graphitic carbon layer prior to RuO deposition (RuO@C@SiO), we retain the high mass activity of the RuO (40-60 mA mg @ η = 330 mV) and preserve the desirable macroscale properties of the 3D scaffold: porous, lightweight, flexible, and inexpensive. The RuO@C@SiO anodes not only achieve the 10 mA cm figure of merit at a low overpotential (η = ∼270 mV), but more importantly they do so while (1) minimizing the mass of catalyst needed to achieve this metric, (2) incorporating the catalyst into a practical electrode design, and (3) improving the long-term stability of the catalyst. Our best-performing anodes achieve state-of-the-art or better performance on the basis of area and mass, and do so with a catalyst density 300-580× less than that of bulk RuO. By limiting the oxidizing potential required to evolve O at the electrode, even at 10 mA cm, we achieve stable activity for 100+ h.
Nickel–iron oxides and oxyhydroxides are among the most active oxygen‐evolution reaction (OER) catalysts in alkaline electrolytes. Compositions rich in Ni are reported to show superior activity, but the establishment of competitive OER activity with lower cost, Fe‐rich analogues is more desirable for metal–air batteries and other devices that will see large‐scale production. Herein, we demonstrate that by controlling pore–solid architecture and the degree of crystallinity, we achieve a single‐phase, Fe‐rich NiFe2Ox catalyst that matches the OER performance metrics previously demonstrated for compositions with higher Ni‐to‐Fe ratios. We also show that OER activity linearly tracks increases in the catalyst surface area, whereas the degree of ex situ surface hydroxylation does not play a significant role. To prepare the pore–solid structured forms, NiFe2Ox gels were synthesized by using an epoxide‐initiated sol–gel method and subsequently processed to aerogels or xerogels. The activities of these two sol–gel‐derived nanostructures were compared with a nanoparticulate analogue with lower specific surface area, prepared by using conventional precipitation methods. The higher surface area and larger pore volume expressed by the NiFe2Ox formed as an aerogel result in a performance‐competitive OER overpotential of 356 mV at a current density of 10 mA cm−2, with an approximately 140 mV improvement relative to the low‐surface‐area, precipitated analogue.
International audienceAs a contribution to a responsive and critical materialist ethics of environments and animals, this essay reexamines the significance of nature and animals in the critical social theory of Theodor Adorno. In response to the anthropocentric stance of intersubjective discourse and recognition in recent figures associated with the Frankfurt School, such as Jürgen Habermas and Axel Honneth, I argue for the ecological import of the aporetic dialectic of nature and society in Adorno and Horkheimer's Dialectic of Enlightenment and Adorno's later works. Adorno's continuing confrontation with the "domination of nature" traces the tensions between the ideological construction and resistance of "nature" as well as the instrumentalization and implicit disruptive promise of sensuous life. These tensions indicate the material and bodily bonds between human and animal happiness and suffering and the ambiguous role of mimesis in both domination and emancipation. Adorno insisted on the critical prospect of an unforced and non-coercive freedom that brings us toward the object and responsibility for socially and historically mediated and non-identical natural life
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