Unraveling the six stages of the current-time curve and the bilayer nanotubes obtained by one-step anodization of Zr.

The application and growth mechanism of anodic TiO nanotubes have been a hot topic in the last ten years, but the formation mechanism of anodic ZrO nanotubes has rarely been studied. In one-step constant voltage anodization of Al and Ti, the typical current-time curve has three stages. Moreover, the current-time curves of the three stages can last for 10 min or even 10 hours, resulting in a single layer of nanotubes with the same diameter due to the constant voltage in one-step anodization.

A review: research progress on the formation mechanism of porous anodic oxides.

Owing to the great development potential of porous anodic oxides (PAO) in many fields, research on their formation mechanisms, fabrication processes and applications has a history of more than ten years. Although compared with research on the fabrication processes and applications of PAO, research on their formation mechanisms started late, several mainstream theories have been formed in the academic community, including the field-assisted dissolution (FAD) theory, the field-assisted ejection (FAE) theory, the self-organization theory, the ionic and electronic current theory and the oxygen bubble mould effect. This review will focus on summarizing the core views of the mainstream mechanisms mentioned above and comparing the explanations for some of their classical experimental phenomena.

Debunking the essential effect of temperature and voltage on the current curve and the nanotube morphology.

The formation mechanism of anodic TiO nanotubes remains to be unclear till now. Many researchers study the influence of temperatures above 0 °C instead of below 0 °C. Few papers before have explained the relationship between the current-time curve and the morphology of the nanotubes.

Evidence of oxygen bubbles forming nanotube embryos in porous anodic oxides.

Anodic TiO nanotubes have been studied widely for two decades because of their regular tubular structures and extensive applications. However, the formation mechanism of anodic TiO nanotubes remains unclear, because it is difficult to find convincing evidence for popular field-assisted dissolution or field-assisted injection theories and the oxygen bubble model. Here, in a bid to find direct evidence that oxygen bubbles form nanotube embryos, a new method is applied to handle this challenge.

N, F-Codoped Microporous Carbon Nanofibers as Efficient Metal-Free Electrocatalysts for ORR.

Currently, the oxygen reduction reaction (ORR) mainly depends on precious metal platinum (Pt) catalysts. However, Pt-based catalysts have several shortcomings, such as high cost, scarcity, and poor long-term stability. Therefore, development of efficient metal-free electrocatalysts to replace Pt-based electrocatalysts is important.