Molybdenum Carbide‐Decorated Metallic Cobalt@Nitrogen‐Doped Carbon Polyhedrons for Enhanced Electrocatalytic Hydrogen Evolution

Abstract

Electrocatalytic hydrogen evolution reaction (HER) based on water splitting holds great promise for clean energy technologies, in which the key issue is exploring cost-effective materials to replace noble metal catalysts. Here, a sequential chemical etching and pyrolysis strategy are developed to prepare molybdenum carbide-decorated metallic cobalt@nitrogen-doped porous carbon polyhedrons (denoted as Mo/Co@N-C) hybrids for enhanced electrocatalytic hydrogen evolution. The obtained metallic Co nanoparticles are coated by N-doped carbon thin layers while the formed molybdenum carbide nanoparticles are well-dispersed in the whole Co@N-C frames. Benefiting from the additionally implanted molybdenum carbide active sites, the HER performance of Mo/Co@N-C hybrids is significantly promoted compared with the single Co@N-C that is derived from the pristine ZIF-67 both in alkaline and acidic media. As a result, the as-synthesized Mo/Co@N-C hybrids exhibit superior HER electrocatalytic activity, and only very low overpotentials of 157 and 187 mV are needed at 10 mA cm in 1 m KOH and 0.5 m H SO , respectively, opening a door for rational design and fabrication of novel low-cost electrocatalysts with hierarchical structures toward electrochemical energy storage and conversion.

Creating Competitive Active Sites on CNTs Walls by N‐Doping and Sublayer Co4N Encapsulating for Efficient Hydrogen Evolution Reaction

“…Since the overpotential and Tafel slope of the catalysts for HER are considered as an important criterion for estimating their electrocatalytic activity. It is noted that the overpotential at 10 mA ⋅ cm −2 and Tafel slope for N−CNTs@Co 4 N@NF show significant advantages for hydrogen evolution reaction when comparing with many other carbon@metallic compound catalysts reported in recent years (Figure c, Table S1).…”

“…Raman spectroscopy was performed for further characterization. The Raman spectra of N−CNTs@Co 4 N@NF and N−CNTs display the D band (∼1361 cm −1 ), G band (∼1583 cm −1 ), 2D band (∼2690 cm −1 ) and D+G band (∼2955 cm −1 ) (Figure a) . The I D /I G ratio of N−CNTs@Co 4 N@NF (1.01) is higher than that of N−CNTs (0.74), which indicates the more ample defects/disorders in the carbon structure possibly owning to the incorporation of N atoms .…”

“…The surface composition of N−CNTs@Co 4 N@NF was studied by XPS measurements (Figure b–3d, S7). The C 1s segment of converted N−CNTs@Co 4 N@NF has four peak binding energies at 284.8 eV, 285.7 eV, 286.7 eV and 288.0 eV, which reflected to the sp 2 C, sp 3 C, C−N and C−O x species (Figure b) . The fewer C−O x species may be caused by adsorption of O 2 or H 2 O.…”

Electrochemical Energy Conversion and Storage with Zeolitic Imidazolate Framework Derived Materials: A Perspective

“…demonstrated the formation of yolk‐shelled structures by chemical etching of ZIF‐67 with molybdate ions. Thermal treatment of the yolk‐shelled nanostructure at 900 °C resulted in the formation of molybdenum carbide decorated metallic cobalt@nitrogen‐doped porous carbon polyhedron . Cobalt nanoparticles (5‐50 nm in size) were coated by N‐doped porous carbon polyhedrons, and (most importantly) the introduced molybdenum carbide nanoparticles were homogenously merged into the entire Co@N‐C nanostructure.…”

“…Thermal treatment of the yolk-shelled nanostructure at 900°C resulted in the formation of molybdenum carbide decorated metallic cobalt@nitrogen-doped porous carbon polyhedron. [56] Cobalt nanoparticles (5-50 nm in size) were coated by N-doped porous carbon polyhedrons, and (most importantly) the intro-duced molybdenum carbide nanoparticles were homogenously merged into the entire Co@N-C nanostructure. The hybrid acted as a superior alkaline HER electrocatalyst by exhibiting a 157 mV overpotential (η 10 ) compared to the 263 mV of Co@N/C.…”