With the speedy exploitation and fossil fuel consumption, environmental deterioration is becoming increasingly obvious. Hydrogen energy is deemed as one of the most promising candidates to substitute fossil fuels, because it is clean, abundant, renewable and eco-friendly. Currently, water splitting devices are used to generate hydrogen. With the flexibility and applicability, they have become the research focus nowadays, and electrocatalysis plays a crucial role in these devices.
In the process of water electrolysis, there are two electrode reactions, namely oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The overall efficiency of hydrogen production is still not ideal due to large overpotentials of both cathode and anode reactions. Therefore, it is of great significance to develop efficient and economical HER electrocatalysts to reduce overpotentials. Although precious metals and/or their oxides show superior electrocatalytic performance of HER/OER, the application of precious metal catalysts is largely restricted by their scarcity and high cost.
Due to high exposure rate of surface atoms, it is feasible to modify 2D materials with surface functionalization, element doping, and defect, and strain or phase engineering. Defect engineering is an effective way to regulate electrocatalytic performance of 2D materials. The existence of defects can not only tune electronic structure, but also increase the number of effective active sites for enhanced HER activity. Therefore, the construction of defect sites in 2D materials plays an important role for the regulation of their catalytic performance.
Recently, a research team led by Jingqi Guan, associate professor of Jilin University (China), reported a review paper on electrocatalysis in Chinese Journal of Catalysis. The review introduces how to construct various defects (i.e. edge defects, vacancy defects, and dopant derived defects) in 2D materials and their structure-function relationship in HER. The main contents of this review include the construction method of defect sites, the structure of defect sites, the relationship between different defect configuration and formation energies, and hydrogen adsorption Gibbs free energy at different adsorption sites.