Electrochemical water splitting comprises two half-reactions: the hydrogen evolution reaction (HER, 2H⁺ + 2e^- → H₂) and the oxygen evolution reaction (OER, H₂O → 2H⁺ + 2e^- + ½O₂).

For HER, platinum-based catalysts are currently the most efficient electro-catalysts with an onset overpotential (η) close to zero;however, the high cost and scarcity of platinum limit its large-scale commercial application. Therefore, low-cost, efficient, and stable non-noble-metal catalysts for HER are required, especially for acidic media because of the strongly acidic conditions met in devices based on proton exchange membrane technology.

—Tavakkoli et al.

The catalyst is composed of single-shell carbon-encapsulated iron nanoparticles (SCEINs) decorated on single-walled carbon nanotubes (SWNTs. The SCEIN/SWNT is synthesized by a novel fast and low-cost aerosol chemical vapor deposition method in a one-step synthesis.

The carbon nanotube conducts electricity extremely well and serves as the support, while the single carbon layer covered iron functions as the catalyst.

In SCEINs the single carbon layer does not prevent desired access of the reactants to the vicinity of the iron nanoparticles but protects the active metallic core from oxidation. This finding opens new avenues for utilizing active transition metals such as iron in a wide range of applications.

—Tavakkoli et al.

Resources

• Mohammad Tavakkoli, Tanja Kallio, Olivier Reynaud, Albert G. Nasibulin, Christoffer Johans,Jani Sainio, Hua Jiang, Esko I. Kauppinen, and Kari Laasonen (2015) “Single-Shell Carbon-Encapsulated Iron Nanoparticles: Synthesis andHigh Electrocatalytic Activity for Hydrogen Evolution Reaction” Angewandte Chemie doi: 10.1002/anie.201411450