In materials science laboratories, common sugars such as sucrose and glucose are undergoing a fascinating transformation. Through high-temperature carbonization, they can be converted into “sugar-derived carbon”—a potentially superior carbon material. However, directly carbonizing sugar often yields products with a dense structure and a low specific surface area, making them difficult to apply in high-end fields. To solve this pain point, scientists have introduced a crucial “magician”: magnesium oxide (MgO). In the preparation of sugar-derived carbon, magnesium oxide is not a mere bystander; rather, it plays a vital role as both a “template” and a “structural architect.” Its application centers on a technique known as the “magnesium oxide template method.”
First, magnesium oxide acts as the “cornerstone” for constructing the microscopic framework. When sugar solutions are mixed with nanoscale magnesium oxide powder, the tiny magnesium oxide particles disperse evenly throughout the sugar solution. As the water evaporates, the sugar acts like paste, tightly coating the surface of each magnesium oxide particle. During the subsequent high-temperature carbonization process, the sugar turns into carbon, while the magnesium oxide particles act like solid stones, supporting the surrounding carbon layer and preventing the carbon structure from collapsing or shrinking at high temperatures, thereby fixing the sugar-derived carbon into a specific morphology.
Second, the most magical function of magnesium oxide lies in its “pore-forming” capability, which constitutes its greatest value in sugar-derived carbon applications. Once carbonization is complete, the magnesium oxide particles that originally occupied space have fulfilled their mission. Taking advantage of the property that magnesium oxide is easily soluble in acid, scientists simply wash the material with hydrochloric acid or sulfuric acid to dissolve and remove the magnesium oxide. The spaces previously occupied by the magnesium oxide particles instantly leave behind vacancies, forming countless regular micropores or mesopores within the sugar-derived carbon.
This porous structure “sculpted” by magnesium oxide breathes new life into the sugar-derived carbon. The originally dense carbon material becomes as loose and porous as a sponge, possessing a huge specific surface area. This enables sugar-derived carbon to store more electrical charges when used as an electrode material for supercapacitors, and to capture more pollutants when used as an adsorbent. Moreover, compared with other template materials like silicon dioxide, magnesium oxide offers unique advantages in the preparation of sugar-derived carbon: its removal conditions are very mild, requiring no highly toxic hydrofluoric acid—only common acid solutions—and the reaction is rapid with minimal damage to the carbon skeleton.
The application of magnesium oxide in sugar-derived carbon is, in essence, an exquisite “art of space.” It uses itself as a mold to shape the sugar-derived carbon, and through its own departure, leaves behind breathing pores for the carbon. It is precisely this “sacrifice” and “fulfillment” by magnesium oxide that transforms inexpensive sugar-derived carbon into high-performance nanomaterials of multiplied value.