Self-Limiting Growth of Single-Layer N-Doped Graphene Encapsulating Nickel Nanoparticles for Efficient Hydrogen Production

Abstract

Effective nonprecious metal catalysts are urgently needed for hydrogen evolution reaction (HER). The hybridization of N-doped graphene and a cost-effective metal is expected to be a promising approach for enhanced HER performance but faces bottlenecks in controllable fabrication. Herein, a silica medium-assisted method is developed for the high-efficient synthesis of single-layer N-doped graphene encapsulating nickel nanoparticles (Ni@SNG), where silica nanosheets molecule sieves tactfully assist the self-limiting growth of single-layer graphene over Ni nanoparticles by depressing the diffusion of gaseous carbon radical reactants. The Ni@SNG sample synthesized at 800 °C shows excellent activity for HER in alkaline medium with a low overpotential of 99.8 mV at 10 mA cm–2, which is close to that of the state-of-the-art Pt/C catalyst. Significantly, the Ni@SNG catalyst is also developed as a binder-free electrode in magnetic field, exhibiting much improved performance than the common Nafion binder-based electrode. Therefore, the magnetism adsorption technique will be a greatly promising approach to overcome the high electron resistance and poor adhesive stability of polymer binder-based electrodes in practical applications.

Self-Templated Formation of Fluffy Graphene-Wrapped Ni5P4 Hollow Spheres for Li-Ion Battery Anodes with High Cycling Stability

“…The characteristic D and G bands of carbon around 1340 and 1585 cm −1 are displayed in the Raman spectrum of Ni 5 P 4 @FG (Figure S5), which are associated with defective carbon and graphitic sp 2 -type carbon, respectively. 27,28 The relative intensity ratio (∼1.05) of the D and G bands (I D /I G ) indicates that the degree of the disorder nature of the FG shell is high because of a lot of defects in the graphene nanosheets, which is ascribed to the nanosized graphene sheets with a large number of edge defects grown over the nickel nanosheets. 27,29 Moreover, the elemental mapping analysis results given in Figure 2f-i show the uniform distribution of C, Ni, and P elements in Ni 5 P 4 @FG, confirming that the Ni 5 P 4 hollow sphere is wrapped in an FG shell.…”

“…Notably, the FG layers contain typical graphene nanosheets with a lattice distance of 0.34 nm (Figure e). The characteristic D and G bands of carbon around 1340 and 1585 cm –1 are displayed in the Raman spectrum of Ni 5 P 4 @FG (Figure S5), which are associated with defective carbon and graphitic sp 2 -type carbon, respectively. , The relative intensity ratio (∼1.05) of the D and G bands ( I D / I G ) indicates that the degree of the disorder nature of the FG shell is high because of a lot of defects in the graphene nanosheets, which is ascribed to the nanosized graphene sheets with a large number of edge defects grown over the nickel nanosheets. , Moreover, the elemental mapping analysis results given in Figure f-i show the uniform distribution of C, Ni, and P elements in Ni 5 P 4 @FG, confirming that the Ni 5 P 4 hollow sphere is wrapped in an FG shell. The EDX analysis indicates that the molar ratio of Ni to P is very close to 5:4 for both the Ni 5 P 4 and Ni 5 P 4 @G samples (Figures S6 and S7), and thermogravimetric (TG) curve shows that the FG layer takes about 5.4 wt % in Ni 5 P 4 @FG (Figure S8).…”

Nickel encapsulated in carbon-dot-derived nanosheets for efficient hydrogen evolution via urea-assisted water electrolysis

“…4i and Table S1 (ESI†) show a comparison of the Ni@NCDs with other Ni-based electrocatalysts reported in the literature, and the results visually reveal the prominent HER catalytic activity of the Ni@NCDs. 35–46…”

Dual interfacial engineering of a Chevrel phase electrode material for stable hydrogen evolution at 2500 mA cm−2

“…Along this direction, the most common way to enhance the adhesion of electrocatalysts on supports is using binders such as Nafion, but it usually cannot provide an adhesion force that is large enough to stand bubble bombardment 11 . Moreover, the use of binder may also block active sites, reduce ionic conductivity and make the electrode aerophilic 12 – 15 , which are harmful to reaction kinetics and bubble detachment.…”