Earth-Abundant Iron Diboride (FeB2) Nanoparticles as Highly Active Bifunctional Electrocatalysts for Overall Water Splitting

5 years ago

Earth-Abundant Iron Diboride (FeB2) Nanoparticles as Highly Active Bifunctional Electrocatalysts for Overall Water Splitting

Hui Li, Chang Lu, Chaochao Dun, Lin Jiang, Peng Wen, David L. Carroll, Junheng Xing, Shiba Adhikari, Qi Li, Scott M. Geyer

Developing efficient, durable, and earth-abundant electrocatalysts for both hydrogen and oxygen evolution reactions is important for realizing large-scale water splitting. The authors report that FeB2 nanoparticles, prepared by a facile chemical reduction of Fe2+ using LiBH4 in an organic solvent, are a superb bifunctional electrocatalyst for overall water splitting. The FeB2 electrode delivers a current density of 10 mA cm−2 at overpotentials of 61 mV for hydrogen evolution reaction (HER) and 296 mV for oxygen evolution reaction (OER) in alkaline electrolyte with Tafel slopes of 87.5 and 52.4 mV dec−1, respectively. The electrode can sustain the HER at an overpotential of 100 mV for 24 h and OER for 1000 cyclic voltammetry cycles with negligible degradation. Density function theory calculations demonstrate that the boron-rich surface possesses appropriate binding energy for chemisorption and desorption of hydrogen-containing intermediates, thus favoring the HER process. The excellent OER activity of FeB2 is ascribed to the formation of a FeOOH/FeB2 heterojunction during water oxidation. An alkaline electrolyzer is constructed using two identical FeB2-NF electrodes as both anode and cathode, which can achieve a current density of 10 mA cm−2 at 1.57 V for overall water splitting with a faradaic efficiency of nearly 100%, rivalling the integrated state-of-the-art Pt/C and RuO2/C. Iron diboride (FeB2) nanoparticles, prepared by a facile chemical reduction of Fe2+ using LiBH4 in an organic solvent, deliver a current density of 10 mA cm−2 (j10) at overpotentials of 61 mV for hydrogen evolution reaction and 296 mV for oxygen evolution reaction in alkaline electrolyte. A full alkaline electrolyzer using two identical FeB2/NF electrodes can achieve j10 at a voltage of 1.57 V for overall water splitting, rivalling the integrated state-of-the-art Pt/C and RuO2/C.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201700513