Nitrogen‐Doped Graphene‐Encapsulated Nickel–Copper Alloy Nanoflower for Highly Efficient Electrochemical Hydrogen Evolution Reaction

Abstract

Development of high‐performance and low‐cost nonprecious metal electrocatalysts is critical for eco‐friendly hydrogen production through electrolysis. Herein, a novel nanoflower‐like electrocatalyst comprising few‐layer nitrogen‐doped graphene‐encapsulated nickel–copper alloy directly on a porous nitrogen‐doped graphic carbon framework (denoted as Nix Cuy @ NG‐NC) is successfully synthesized using a facile and scalable method through calcinating the carbon, copper, and nickel hydroxy carbonate composite under inert atmosphere. The introduction of Cu can effectively modulate the morphologies and hydrogen evolution reaction (HER) performance. Moreover, the calcination temperature is an important factor to tune the thickness of graphene layers of the Nix Cuy @ NG‐NC composites and the associated electrocatalytic performance. Due to the collective effects including unique porous flowered architecture and the synergetic effect between the bimetallic alloy core and graphene shell, the Ni3Cu1@ NG‐NC electrocatalyst obtained under optimized conditions exhibits highly efficient and ultrastable activity toward HER in harsh environments, i.e., a low overpotential of 122 mV to achieve a current density of 10 mA cm−2 with a low Tafel slope of 84.2 mV dec−1 in alkaline media, and a low overpotential of 95 mV to achieve a current density of 10 mA cm−2 with a low Tafel slope of 77.1 mV dec−1 in acidic electrolyte.

WOx‐Surface Decorated PtNi@Pt Dendritic Nanowires as Efficient pH‐Universal Hydrogen Evolution Electrocatalysts

“…[ 4–7 ] To minimize the overpotential and boost the kinetics of HER, an optimal electrocatalyst is highly desirable. [ 8–10 ] Although non‐platinum (non‐Pt) based nanomaterials have recently been presenting well for HER catalysis, [ 11–19 ] the HER performance of Pt‐based materials are still second to none, considering its optimal interaction with hydrogen adsorbates (H ad ) on the surface. [ 20–24 ] However, the HER kinetics of Pt‐based electrocatalysts in alkaline medium are much lower than those in acid medium due to distinct reaction pathways of HER, especially Volmer step, in different conditions.…”

Coupling NiCo Alloy and CeO2 to Enhance Electrocatalytic Hydrogen Evolution in Alkaline Solution

“…In terms of overpotential at 10 mA cm −2 and Tafel slope, NiCo-CeO 2 /GP also outperforms most of the reported (Figure 3d) as well as other HER electrocatalysts (Table S2, Supporting Information). [16][17][18][40][41][42][43] To further estimate the intrinsic activities of the synthesized electrocatalysts, electrochemical active surface areas (ECSAs) of electrodes derived from the double-layer capacitances (C dl ) were tested ( Figure S15, Supporting Information). As shown in Figure S16, Supporting Information, NiCo-CeO 2 /GP shows the largest C dl and thus possesses the highest ECSA that is relative to graphite plate (see Supporting Information for details).…”

Facile synthesis of nickel–copper hollow spheres as efficient bifunctional electrocatalysts for overall water splitting

“…However, the peaks (111) and (200) shift to the lower angle by increasing the amount of Cu in Ni x Cu y @C, suggesting that Cu is indeed incorporated into Ni to form a Ni x Cu y alloy. 41,42 In addition, XPS analysis (Fig. S3a, ESI †) indicates that the Ni 2p 3/2 region displays two dominant peaks of Ni 0 and Ni-O in which the Ni-O species is ascribed to the inevitable surface oxidation exposed in the air.…”

“…S17e and f, ESI †), indicating that Ni 4 Cu 2 is stable in basic solutions during the HER. 42,46,58 On the anode side, the nanostructure of Ni 4 Cu 2 @C also remains intact (Fig. S18a and b, ESI †).…”