Numerous research efforts have been devoted to replicate the functioning of biological ion pumps in nanofluidic devices. Unlike previous reports of cationic pumps, positively charged CoAl layered double hydroxide (CoAl LDH) is exploited here for uphill pumping of anionic species. Nanofluidic membranes prepared by self-assembling exfoliated layers of CoAl LDH exhibit excellent anionic transport characteristics. At the surface-chargegoverned regime, the positively charged CoAl LDH membrane (p-LDHM) showed a remarkable OH − ion conductivity of ∼2 mS cm −1 . The remarkable mobility of OH − ions (4 × 10 −4 cm 2 V −1 S −1 ) in the atomically thin channel of p-LDHM is attributed to the tiny activation energy (0.09 eV) required for Grotthuss-like hopping of the ions between the positive charges of densely packed CoAl LDH layers. The lamellar p-LDHM was also found to be suitable for energy harvesting via salinity gradient, and a power density up to 0.7 Wm −2 was achieved under a 1000-fold concentration gradient. The triangular p-LDHM displays a diode-like nonlinear I−V curve, attributed to a combination of unipolar conductivity of counterions inside the two-dimensional (2D) nanochannels and geometrical asymmetry. The triangular p-LDHM pumps anions against the concentration gradient (up to 1000-fold), under fluctuating external potentials with a mean value of zero.
Owing to their unique advantages like environmental compatibility, low cost, and high energy density, metal–water batteries are gaining a great deal of attention. The principles of metal–water batteries were applied here to develop a sustainable pressure-responsive energy delivery system. Application of a gentle pressure of 56 kPa on agar and a glycerol-based hydrogel membrane sandwiched between the aluminum foil and the nanofluidic V2O5 membrane (Al-gel-VO device) generates open-circuit voltage up to 1.3 V accompanied by an output current of 85 μA (power density = 0.45 W m–2). The output power of Al-gel-VO can be further improved by tuning parameters like lateral dimensions of the layers, applied pressure, and ionic conductivity of the gel membrane. Remarkably, under ambient conditions, the hydrogel and V2O5-based devices can provide a constant potential difference up to five consecutive days. Unlike typical humidity-powered energy systems, the energy output of the current device is resistant to the diurnal variations in environmental conditions. Remarkably, both gel and V2O5 membranes can be completely regenerated after damage caused by prolonged use or accidents without any deterioration in the energy efficiencies. Moreover, the Al-gel-VO devices can also be connected in series (or parallel) to add up the voltage (or current) values of the individual devices.
We demonstrate herein the catalytic performance of unsupported Ni(OH)2 nanoparticles towards the dehydrogenation of primary alcohols to corresponding acids under aerobic conditions in refluxing toluene. An assortment of aromatic and aliphatic carboxylic acids/acids salts was prepared from corresponding alcohols in moderate to excellent yields. Interestingly, the protocol can also be employed to synthesize carboxylic acids on a gram scale, demonstrating the practical utility of the method. Mechanistic studies suggest that the reaction proceeds through an acceptorless dehydrogenation strategy and follow both Cannizzaro and catalytic dehydrogenative path. Broad substrate scope, operational simplicity, low cost, and reusability are the most interesting features of the current heterogeneous catalytic protocol described herein.
In recent years, the application of ionic thermoelectric (TE) materials to convert low‐grade waste heat into electricity has become a subject of intense scientific research. However, most of the efforts are focused on organic polyelectrolytes or ionic‐liquids embedded in polymeric gels. Here, for the first time, it is demonstrated that nanofluidic membranes of reconstructed layered materials like vanadium pentoxide (V2O5) exhibit excellent ionic‐TE characteristics. The high Seebeck coefficient (S = 14.5 ± 0.5 mV K‐1) of the V2O5 membrane (VO‐M) is attributed to temperature gradient‐induced unidirectional transport of protons through the percolated network of 2D nanofluidic channels. The TE characteristics of VO‐M show nearly 80% improvement (S = 26.3 ± 0.7 mV K‐1) upon functionalizing its percolated network with ionic polymers like poly(4‐styrenesulfonic acid) (PSS). Further, unlike organic polymer‐based TE systems, VO‐M not only sustains exposure to high temperatures (≈200 °C, 5 min) but also protects the PSS molecules intercalated into its interlayer space. Moreover, V2O5‐based TE materials can self‐repair any damage to their physical structure with the help of a tiny water droplet. Thus, nanofluidic membranes of reconstructed layered materials like VO‐Ms demonstrate vast robustness and great ionic‐TE performance, which can provide a novel platform for scientific studies and futuristic applications.
The recent trend in thermoelectric literature suggests ionic thermoelectric (i-TE) materials are ideal for directly converting low-grade waste heat into electricity. Here, we developed a unique platform for i-TE studies...
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