Transition Metal Carbides and Nitrides As Electrocatalysts for Hydrogen and Oxygen Evolution Reactions

Global demand to achieve carbon-neutral energy production and utilization has raised a trend of searching for a fuel that minimizes the production of CO 2 . From this viewpoint, hydrogen is considered as an ideal fuel as it does not contain carbon in its formula. Meanwhile, the challenge remains in the process for hydrogen production, as it is energetically up-hill and thereby produces CO 2 unless a combination of renewable energy and water splitting is used. There are a number of components that constitute a water electrolyzer, but its economic feasibility is largely challenged by noble metal electrocatalysts used for facilitation of hydrogen and oxygen evolution reactions. For this reason, significant efforts have been put to develop low-cost materials that could substitute costly catalysts. In-depth understandings on correlations between the electronic structure and the electrocatalytic activity led to the interest toward transition metal carbide and nitride materials, as they own electronic structures that mimic those of catalytic noble metals. These materials did manifest decent performances, though there are some remaining issues including the energy-intensive synthetic process. Herein, nanostructured transition metal carbide and nitride produced by facile preparation methods are introduced. Self-supported carbides synthesized via electrochemical structuring followed by thermal carburization are applied in hydrogen evolution reaction, wherein decent catalytic activity and excellent durability are achieved. In addition, nitrides prepared at an ambient-temperature and environmentally-benign condition are utilized for oxygen evolution reaction, which manifested high performance both in terms of activity and long-term stability. Based on thorough characterization of carbides and nitrides, their physicochemical properties and electrochemical behaviors, and the relationships among them are discussed.