Among the various approaches to grow semiconducting oxide nanowires, the thermal oxidation procedure is considered a simple, efficient, and fast method that allows the synthesis of micro and nanostructured arrangements with controlled size and morphology. In the work reported in this paper, long ZnO nanowires were synthesized on the surface of oxidized high-purity Zn foils by heating in air at different rates and temperatures. The size and morphology investigated by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) for a sample heated at 620 °C with heating rate of 20 °C/min reveal the growth of long ZnO nanowires with length of ∼50 μm and average diameter of 74 nm grown along the ⟨112̅ 0⟩ direction with high population density. Results with different heating rates indicates that this parameter is determinant in tuning the size, morphology, and population density of nanowires. X-ray diffraction (XRD) shows patterns for both ZnO and metallic Zn with preferential orientation, whereas perturbed angular correlation (PAC) measurements using 111 In( 111 Cd) probe nuclei indicate that probe nuclei occupy only Zn sites in the preferential oriented metallic zinc. However, for samples submitted to high-temperature heating (820 and 1000 °C), XRD yields only the ZnO pattern and, amazingly, PAC continues showing probe nuclei only at metallic Zn sites indicating the presence of thin regions of highly oriented Zn trapped between grains of ZnO. Moreover, this strong preference of indium atoms (of parent radioactive 111 In) here revealed helps to understand the oxidation mechanism and the growth of the nanowires.

Hydrogen Peroxide (H2O2) is a versatile and environmentally friendly chemical oxidant with a remarkably diverse range of applications, including fine chemical synthesis, first aid kits for disinfection, pulp and textile bleaching, wastewater treatment and others. Industrial production of H2O2 is based on the anthraquinone oxidation/reduction process, which consumes a lot of energy, requires complex and large-scale equipment, and mass extraction solvents, generating an enormous waste. There is a general demand for a more decentralised infrastructure, where energy conversion and chemical synthesis are conducted closer to the point of consumption. In this context, developing an electrochemical process to partially reduce O2 to H2O2 (O2 + 2H+/e- → H2O2) in an acidic medium would be an attractive strategy that could be carried out under ambient conditions using renewable energies. However, practical and economic electrocatalysts that exhibit high activity and selectivity for hydrogen peroxide production is to be developed. A series of M-N/C catalysts (M = Fe, Co, and Cu) were prepared in the present study. The performance (activity and selectivity) of these catalysts for the oxygen reduction reaction was investigated in the potential window of 0.2 V to 1.0 V vs. the Reversible Hydrogen Electrode (RHE). Electrochemical measurements demonstrated that the Co-N/C [c] electrocatalyst exhibits high ORR activity and exceptional selectivity for hydrogen peroxide production (92% at 0.5 V vs. RHE).

When hydrogen is produced by electrolysis the possibility of water stress in some populations and scarcity of precious metals for catalyst production are seen as future barriers. The use of non-precious metal catalysts allied to direct saltwater splitting reduce the pressure on scarce resources. Here, four Metal-Nitrogen-Carbon (M-N-C) catalysts were synthesized with metal salts of Co, Fe, Ni and FeNi, with 1,5-diaminonhaptalene as N-C source. These catalysts were compared with a blank N-C without metal and a Pt/C commercial catalyst. Tests were conducted in electrolyte solution 0.5 M of H2SO4 and 0.5 M of NaCl. Results showed limited activity towards Hydrogen Evolution Reaction (HER) compared with Pt/C and other non precious metal catalysts. Nevertheless, points out trends for better catalyst synthesis as improved activity of FeNi catalyst in acidic media and saltwater.

When hydrogen is produced by electrolysis the possibility of water stress in some populations and scarcity of precious metals for catalyst production are seen as future barriers. The use of nonprecious metal catalysts allied to direct saltwater splitting reduce the pressure on scarce resources. Here, four Metal-Nitrogen-Carbon (M-N-C) catalysts were synthesized with metal salts of Co, Fe, Ni and FeNi, with 1,5-diaminonhaptalene as N-C source. These catalysts were compared with a blank N-C without metal and a Pt/C commercial catalyst. Tests were conducted in electrolyte solution 0.5 M of H2SO4 and 0.5 M of NaCl. Results showed limited activity towards Hydrogen Evolution Reaction (HER) compared with Pt/C and other non-precious metal catalysts. Nevertheless, points out trends for better catalyst synthesis as improved activity of FeNi catalyst in acidic media and saltwater.