Lateral epitaxial overgrowth (LEO) of ZnO has been demonstrated in water at 90 °C. The process starts with hydrothermal epitaxial growth of ZnO(0001) on MgAl2O4(111), followed by channel stamping of photoresist to define “growth windows”. LEO films grow in zinc‐precursor solutions at pH 10.9; sodium citrate addition controls out‐of‐plane growth. Transmission electron microscopy indicates threading dislocation reductions from ∼ 2 × 1010 to < 2 × 108 cm–2 from the window to the wing regions. Microphotoluminescence and Hall‐effect measurements indicate improved material quality. Wing tilt was observed. Double LEO demonstrates the possibility of complete dislocation reduction.

Orthorhombic KNbO 3 and NaNbO 3 powders were hydrothermally synthesized in KOH and NaOH solutions (6.7-15 M) at 150 and 200°C. An intermediate hexaniobate species formed first before eventually converting to the perovskite phase. For synthesis in KOH solutions, the stability of the intermediate hexaniobate ion increased with decreasing KOH concentrations and temperatures. This led to significant variations in the induction periods and accounted for the large disparity in the mass of recovered powder for different processing parameters. It is also believed that protons were incorporated in the lattice of the as-synthesized KNbO 3 powders as water molecules and hydroxyl ions.

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The selective electroreduction of CO2 to formate (or formic acid) is of great interest in the field of renewable‐energy utilization. In this work, we designed a sulfur‐doped Cu2O‐derived Cu catalyst and showed that the presence of sulfur can tune the selectivity of Cu significantly from the production of various CO2 reduction products to almost exclusively formate. Sulfur is doped into the Cu catalysts by dipping the Cu substrates into ammonium polysulfide solutions. Catalyst films with the highest sulfur content of 2.7 at % showed the largest formate current density (jHCOO- ) of −13.9 mA cm−2 at −0.9 V versus the reversible hydrogen electrode (RHE), which is approximately 46 times larger than that previously reported for Cu(110) surfaces. At −0.8 V versus RHE, the faradaic efficiency of formate was maintained at approximately 75 % for 12 h of continuous electrolysis. Through the analysis of the evolution of the jHCOO- and jnormalH2 values with the sulfur content, we show that sulfur doping increases formate production and suppresses the hydrogen evolution reaction. Ag–S and Cu–Se catalysts did not exhibit any significant enhancement towards the reduction of CO2 to formate. This demonstrates clearly that sulfur and copper acted synergistically to promote the selective formation of formate. A hypothesis about the role of sulfur is proposed and discussed.