3D core–shell nanostructures of few-layer NiFe LDH nanosheets grown on Cu nanowires are fabricated toward highly efficient overall water splitting.

Water electrolysis is an advanced energy conversion technology to produce hydrogen as a clean and sustainable chemical fuel, which potentially stores the abundant but intermittent renewable energy sources scalably. Since the overall water splitting is an uphill reaction in low efficiency, innovative breakthroughs are desirable to greatly improve the efficiency by rationally designing non-precious metal-based robust bifunctional catalysts for promoting both the cathodic hydrogen evolution and anodic oxygen evolution reactions. We report a hybrid catalyst constructed by iron and dinickel phosphides on nickel foams that drives both the hydrogen and oxygen evolution reactions well in base, and thus substantially expedites overall water splitting at 10 mA cm−2 with 1.42 V, which outperforms the integrated iridium (IV) oxide and platinum couple (1.57 V), and are among the best activities currently. Especially, it delivers 500 mA cm−2 at 1.72 V without decay even after the durability test for 40 h, providing great potential for large-scale applications.

We prepared iodine-doped n-type SnSe polycrystalline by melting and hot pressing. The prepared material is anisotropic with a peak ZT of ~0.8 at about 773 K measured along the hot pressing direction. This is the first report on TE properties of n-type Sn chalcogenide alloys.With increasing content of iodine, the carrier concentration changed from 2.3×10 17 cm -3 (p-type)to 5.0×10 15 cm -3 (n-type) then to 2.0×10 17 cm -3 (n-type). The decent ZT is mainly attributed to the intrinsically low thermal conductivity due to the high anharmonicity of the chemical bonds like those in p-type SnSe. By alloying with 10 atm. % SnS, even lower thermal conductivity and an enhanced Seebeck coefficient were achieved, leading to an increased ZT of ~1.0 at about 773 K measured also along the hot pressing direction.

Conventional theory predicts that ultrahigh lattice thermal conductivity can only occur in crystals composed of strongly bonded light elements, and that it is limited by anharmonic three-phonon processes. We report experimental evidence that departs from these long-held criteria. We measured a local room-temperature thermal conductivity exceeding 1000 watts per meter-kelvin and an average bulk value reaching 900 watts per meter-kelvin in bulk boron arsenide (BAs) crystals, where boron and arsenic are light and heavy elements, respectively. The high values are consistent with a proposal for phonon-band engineering and can only be explained by higher-order phonon processes. These findings yield insight into the physics of heat conduction in solids and show BAs to be the only known semiconductor with ultrahigh thermal conductivity.

Thermoelectric properties are heavily dependent on the carrier concentration, and therefore the optimization of carrier concentration plays a central role in achieving high thermoelectric performance.

Mg 3Àx Na x Sb 2 has been prepared successfully by mechanical alloying plus hot pressing to investigate the effects of Na doping on the thermoelectric properties. Thermoelectric properties were characterized by the Seebeck coefficient, electrical resistivity, thermal conductivity, and thermoelectric figure of merit (ZT) from 298 to 773 K. Transport measurements reveal that an optimum doping of 1.25 at.% Na on Mg achieved ZT of 0.6 at 773 K. The enhancement in ZT is attributed to increased carrier concentration and power factor. The low cost, abundance, and nontoxicity makes this material a potentially promising thermoelectric material for power generation at a heat source below 773 K.

Transparent oxides are essential building blocks to many technologies, ranging from components in transparent electronics 1,2 , transparent conductors 3,4 , to absorbers and protection layers in photovoltaics and photoelectrochemical devices 5,6 . However, thus far, it has been difficult to develop p-type oxides with wide band gap and high hole mobility; current state-of-art transparent p-type oxides have hole mobility in the range of < 10 cm 2 /V·s 7,8 , much lower than their n-type counterparts 9-11 . Using high-throughput computational screening to guide the discovery of novel oxides with wide band gap and high hole mobility, we report the computational identification and the experimental verification of a bismuth-based double-perovskite oxide that meets these requirements.Our identified candidate, Ba 2 BiTaO 6 , has an optical band gap larger than 4 eV and a Hall hole mobility above 30 cm 2 /V·s. We rationalize this finding with molecular orbital intuitions; Bi 3+ with filled s-orbitals strongly overlap with the oxygen p, increasing the extent of the metal-oxygen covalency and effectively reducing the valence effective mass, while Ta 5+ forms a conduction band with low electronegativity, leading to a high band gap beyond the visible range. Our concerted theory-experiment effort points to the growing utility of a data-driven materials discovery and the combination of both informatics and chemical intuitions as a way to discover future technological materials.

The use of renewable electricity to prepare materials and fuels from abundant molecules offers a tantalizing opportunity to address concerns over energy and materials sustainability. The oxygen evolution reaction (OER) is integral to nearly all material and fuel electrosyntheses. However, very little is known about the structural evolution of the OER electrocatalyst, especially the amorphous layer that forms from the crystalline structure. Here, we investigate the interfacial transformation of the SrIrO3 OER electrocatalyst. The SrIrO3 amorphization is initiated by the lattice oxygen redox, a step that allows Sr2+ to diffuse and O2− to reorganize the SrIrO3 structure. This activation turns SrIrO3 into a highly disordered Ir octahedral network with Ir square-planar motif. The final SryIrOx exhibits a greater degree of disorder than IrOx made from other processing methods. Our results demonstrate that the structural reorganization facilitated by coupled ionic diffusions is essential to the disordered structure of the SrIrO3 electrocatalyst.