Porous Single-Crystalline Molybdenum Nitride Monoliths at the Centimeter Scale Surpass Platinum for all pH Hydrogen Evolution.

Abstract

Platinum is widely used in the important components in most electrochemical energy conversion systems while as a noble metal it faces the inevitable challenge of limited reserves. Herein, porous single-crystalline (PSC) molybdenum nitride (MoN) monoliths are reported at the centimeter scale that surpass platinum for all-pH hydrogen evolution. Free-standing PSC MoN electrode with the pore size of ≈6 nm and porosity of ≈72% present both noble-metal-like electronic structure and unsaturated Mo─N coordination structures at surface, contributing to remarkably high intrinsic electrocatalytic activity. The unprecedented overpotentials of as low as 13 and 11 mV are presented at the geometrical current density of 10 mA cm^-2 for hydrogen evolution in H₂SO₄ (pH 0) and KOH (pH 14) media, respectively, which is dramatically superior to commercial Pt electrodes. As a result of the structural stability, the outstanding long-term durability for all pH hydrogen evolution is demonstrated without visible degradation in a continuous operation for 300 h.