The development of efficient and low-cost electrocatalysts for oxygen evolution reaction is critical for improving the water electrolysis efficiency. Here we report a strategy using Fe substitution to enable the inactive spinel CoAl 2 O 4 to become highly active and superior to the benchmark IrO 2. The Fe substitution is revealed to facilitate the surface reconstruction into active Co oxyhydroxides under OER conditions. It also activates the deprotonation on the reconstructed oxyhydroxide to induce negatively charged oxygen as active site, thus significantly enhancing the OER activity of CoAl 2 O 4. Furthermore, it promotes the pre-oxidation of Co and introduces great structural flexibility due to the uplift of the O 2p levels. This results in an accumulation of surface oxygen vacancy along with lattice oxygen oxidation that terminates as Al 3+ leaches, preventing further reconstruction. We showcase a promising way to achieve tunable electrochemical reconstruction by optimizing the electronic structure for low-cost and robust spinel oxide OER catalysts.

We describe a versatile and scalable strategy toward long-range and periodically ordered mesoporous alumina (Al 2 O 3 ) structures by evaporationinduced self-assembly of a structure-directing ABA triblock copolymer (F127) mixed with aluminum tri-sec-butoxide-derived sol additive. We found that the separate preparation of the alkoxide sol−gel reaction before mixing with the block copolymer enabled access to a relatively unexplored parameter space of copolymerto-additive composition, acid-to-metal molar ratio, and solvent, yielding ordered mesophases of two-dimensional (2D) lamellar, hexagonal cylinder, and 3D cage-like cubic lattices, as well as multiscale hierarchical ordered structures from spinodal decomposition-induced macro-and mesophase separation. Thermal annealing in air at 900 °C yielded well-ordered mesoporous crystalline γ-Al 2 O 3 structures and hierarchically porous γ-Al 2 O 3 with 3D interconnected macroscale and ordered mesoscale pore networks. The ordered Al 2 O 3 structures exhibited tunable pore sizes in three different length scales, <2 nm (micropore), 2−11 nm (mesopore), and 1−5 μm (macropore), as well as high surface areas and pore volumes of up to 305 m 2 /g and 0.33 cm 3 /g, respectively. Moreover, the resultant mesoporous Al 2 O 3 demonstrated enhanced adsorption capacities of carbon dioxide and Congo red dye. Such hierarchically ordered mesoporous Al 2 O 3 are well-suited for green environmental solutions and urban sustainability applications, for example, hightemperature solid adsorbents and catalyst supports for carbon dioxide sequestration, fuel cells, and wastewater separation treatments.

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This report describes a simple one-pot soft-templating and ammonolysis-free approach to synthesize mesoporous crystalline titanium oxynitride by combining block copolymerdirected self-assembly with metal sol and urea precursors. Pluronic F127 triblock copolymer was employed to structure-direct titanium-oxo-acetate sol nanoparticles and ureaformaldehyde into ordered hybrid mesostructured monoliths. The hybrid composites were directly converted into mesoporous crystalline titanium oxynitride and retained macroscale monolithic integrity up to 800 °C under nitrogen. Notably, the urea-formaldehyde additive provided nitrogen and rigid support to the inorganic mesostructure during crystallization. The resultant mesoporous titanium oxynitride exhibited good electrochemical catalytic activity toward hydrogen evolution reaction in 1 M KOH aqueous medium under applied bias. Our results suggest an inexpensive and safe pathway to generate ordered mesoporous crystalline metal oxynitride structures suitable for catalyst and energy-storage applications.

We have investigated the role of threading dislocations in pit formation during stressing of AlGaN/GaN on Si high electron mobility transistors under high reverse bias. Upon stressing, the drain current saturation (I D-saturation ) decreases over time. The amount of I D-saturation degradation correlates well with pit formation at the gate-edge, where the electric field is the highest. Using a transmission electron microscope weak-beam technique, it is found that pits tend to nucleate at threading dislocations that have a screw component, even when these dislocations are at locations away from the gate-edge. An explanation based on an electrochemical oxidation model is proposed.