Enhancing Electrocatalytic Activity for Hydrogen Evolution by Strongly Coupled Molybdenum Nitride@Nitrogen-Doped Carbon Porous Nano-Octahedrons

Abstract

Developing highly efficient and affordable noblemetal-free catalysts toward the hydrogen evolution reaction (HER) is an important step toward the economical production of hydrogen. As a nonprecious-metal catalyst for the HER, molybdenum nitride (MoN) has excellent corrosion resistance and high electrical conductivity, but its catalytic activity is still inadequate. Here we report our findings in dramatically enhancing the HER activity of MoN by creating porous MoN@nitrogendoped carbon (MoN-NC) nano-octahedrons derived from metal−organic frameworks (MOFs). The composite catalyst displays remarkably high catalytic activity, demonstrating a low overpotential of 62 mV at a current density of 10 mA cm −2 (η 10 ), a small Tafel slope of 54 mV dec −1 , and a large exchange current density of 0.778 mA cm −2 while maintaining good stability. The enhancement in catalytic properties is attributed to the unique nanostructure of the MoN, the high porosity of the electrode, and the synergistic effect between the MoN and the nitrogendoped carbon substrate. The performances are among the best ever reported for nonprecious-metal-based electrocatalysts (comparable to those of a 20% Pt/C commercial catalyst), making the porous MoN-NC nano-octahedrons some of the most active and acid-stable electrocatalysts for the HER.

Activating the MoS2 Basal Plane by Controllable Fabrication of Pores for an Enhanced Hydrogen Evolution Reaction

“…Calculated from the polarization curves, Tafel plots of pristine MoS 2 , porous MoS 2 , and 20 % Pt/C are shown in Figure c. The Tafel equation is employed to fit the linear portion of the plots: η = b log| j |+ a , in which η , j , b , and a denote the overpotential, Tafel slope, current density, and a constant, respectively. The Tafel slope of the Pt/C catalyst is ≈34 mV dec −1 , in line with the value as reported in the previous study . The Tafel slopes are calculated to be 78 (MoS 2 ‐1), 62 (MoS 2 ‐3), 84 (MoS 2 ‐5), and 89 (MoS 2 ‐7) mV dec −1 , which are apparently lower than that of pristine MoS 2 nanosheets (99 mV dec −1 ), demonstrating significantly improved catalytic activity of the proper engineered porous basal plane of the MoS 2 nanosheets compared to the pure MoS 2 .…”

Earth‐Abundant Transition‐Metal‐Based Electrocatalysts for Water Electrolysis to Produce Renewable Hydrogen

“…Co 3 O 4 could be directly convertedi nto cobaltn itride (CoN) by using N 2 radio frequency( RF) plasma treatment. [66] Abghoui and Skulason have investigated the possibility of metal mononitrides for catalyzingt he HER through DFT calculations (Figure1 1). [65] Sasaki and coworkers have synthesized MoN and NiMoN x nanosheets for HER ( Figure 10).…”

Rational Microstructure Design on Metal–Organic Framework Composites for Better Electrochemical Performances: Design Principle, Synthetic Strategy, and Promotion Mechanism

“…e) Polarization curves ( iR compensated) in 0.5 m H 2 SO 4 at a scan rate of 5 mV s −1 . Reproduced with permission . Copyright 2017, American Chemical Society.…”