Nanoarchitectonics with the amorphous rhenium phosphide compounds for enhanced catalytic activity of hydrogen evolution reaction

Abstract

Rhenium can be used as a highly active electrocatalyst for the hydrogen evolution reaction (HER) owing to its theoretically large exchange current and optimum binding energy in the Sabatier plot. However, as rhenium metal cannot achieve a high performance owing to few active sites, rhenium must be transmuted to modulate its catalytic activity. In this study, we first fabricated an amorphous rhenium phosphide/carbon composite as an electrocatalyst for the HER using a simple annealing process. The obtained amorphous rhenium phosphide acts as an efficient HER electrocatalyst with an overpotential of 79.1 mV at a current density of 10 mA cm−2 in 0.5 M H2SO4 and the corresponding Tafel slope of 55 mV dec−1, thereby outperforming the crystalline phase with the overpotential and Tafel slope of 109 mV and 67 mV dec−1, respectively. The 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) precursor has a strong ability to chelate metal ions and provides a phosphorus source to prepare rhenium phosphide. The phosphorization of rhenium metal leads to enhanced catalytic activity, providing abundant and efficient active sites for catalysis. These amorphous species might be beneficial for HER because of their disordered atomic arrangement and abundant defect sites, indicating a higher catalytic activity than that of the crystalline phase.