Cobalt‐Embedded Nitrogen‐Rich Carbon Nanotubes Efficiently Catalyze Hydrogen Evolution Reaction at All pH Values

Abstract

Despite being technically possible, splitting water to generate hydrogen is still practically unfeasible due mainly to the lack of sustainable and efficient catalysts for the half reactions involved. Herein we report the synthesis of cobalt-embedded nitrogen-rich carbon nanotubes (NRCNTs) that 1) can efficiently electrocatalyze the hydrogen evolution reaction (HER) with activities close to that of Pt and 2) function well under acidic, neutral or basic media alike, allowing them to be coupled with the best available oxygen-evolving catalysts-which also play crucial roles in the overall water-splitting reaction. The materials are synthesized by a simple, easily scalable synthetic route involving thermal treatment of Co(2+) -embedded graphitic carbon nitride derived from inexpensive starting materials (dicyandiamide and CoCl2 ). The materials' efficient catalytic activity is mainly attributed to their nitrogen dopants and concomitant structural defects.

Acid promoted Ni/NiO monolithic electrode for overall water splitting in alkaline medium

“…In addition, the NF-120 exhibits remarkably high activity with an onset potential of~73 mV and an overpotential of 160 mV vs. RHE at the current density of 10 mA cm −2 (NF-60, NF-90 and the bare NF display overpotentials of 195, 176 and 288 mV, respectively). This overpotential is comparable to or even smaller than those of many reported values for non-Pt HER catalysts in basic aqueous media, including CoNRCNTs (370 mV) [40], MoB (225 mV) [41], WP (250 mV) [28], porous Co-based film (375 mV) [42], MoP (276 mV) [43], and WN NAs/CC (285 mV) [44], (see Fig. 4b and Table S1 in the Supplementary information for more details).…”

Electrocatalysts for Hydrogen Evolution in Alkaline Electrolytes: Mechanisms, Challenges, and Prospective Solutions

“…Carbon materials, such as carbon nanotubes (CNTs), graphene, graphene oxide (GO), and porous carbon materials extracted from artificial and natural carbon complexes not only increase the dispersity of the active components but also improve the conductivity of the hybrid catalysts due to their huge surface area, tunable molecular structures and superior electrical conductivity 51, 87, 88, 89. Typically, Co‐CNTs was designed as a highly active and stable electrocatalyst which is composed of Co embedded in nitrogen‐rich carbon nanotubes 90. The Co‐CNTs showed only marginally lower onset potential by −0.05 to −0.1 V compared to Pt/C and delivers higher current density at slightly higher applied potentials than their onset potential (←0.5 V vs RHE) under the same condition in 1 m KOH, resulting in a better HER activity than the commercial Pt/C.…”

“…However, by controlling the sp 2 and sp 3 hybridization degree the catalytic properties of the carbon based materials can be tuned. Further the incorporation of heteroatoms (metallic or nonmetallic elements) in the lattice planes of carbon nanostructure is also widely used to mobilize the electronic movements and break the surface neutrality, especially in case of graphitic carbon where heteroatoms can alter the density of state (DOS) of carbon and alter its electronic atmosphere 90, 136, 137. This kind of modification can enhance their abilities for high electrical conductions, surface reactions and active sites for chemical conversions and chemo/physio adsorptions of molecular components.…”

Mo2C nanoparticles embedded within bacterial cellulose-derived 3D N-doped carbon nanofiber networks for efficient hydrogen evolution

“…41 Non-precious HER catalysts that work well in basic or neutral media are highly desirable to realize overall electrochemical water splitting by inexpensive electrocatalysts. Therefore, the HER activity of Mo 2 C@N-CNFs was also investigated in 1 M KOH (pH 14) and 0.1 M PBS (pH 7) solutions (Supplementary Figure S15).…”