Abstract: A carbon semi-tube (CST) is a novel carbon morphology and represents one of the most advanced carbon materials in the field of nanotechnology. Its discovery has enriched the carbon material family. The successful development of semi-tubular non/low noble metal electrocatalysts for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and electrochemical carbon dioxide reduction reaction (CO₂RR) can provide very promising insights into the future uses of CST in many electrochemical energy technologies, such as fuel cells, batteries, supercapacitors, water electrolysis, and CO₂-electrolysis.Its unique nanostructure has many notable properties, including semi-tubular morphology, high degree of openness, adjustable curvature, large specific surface area, abundant pores, good electronic/ionic conductivity, and an ordered structure. This new material is expected to have many applications, especially in the area of electrochemical energy storage and conversion.

Key words: Carbon semi-tube, ORR, HOR, HER, OER, CO₂RR, Electrocatalysis, Electrochemical energy