Active Edge Sites Engineering in Nickel Cobalt Selenide Solid Solutions for Highly Efficient Hydrogen Evolution

Abstract

An effective multifaceted strategy is demonstrated to increase active edge site concentration in Ni0.33Co0.67Se2 solid solutions prepared by in situ selenization process of nickel cobalt precursor. The simultaneous control of surface, phase, and morphology result in as‐prepared ternary solid solution with extremely high electrochemically active surface area (Cdl = 197 mF cm−2), suggesting significant exposure of active sites in this ternary compound. Coupled with metallic‐like electrical conductivity and lower free energy for atomic hydrogen adsorption in Ni0.33Co0.67Se2, identified by temperature‐dependent conductivities and density functional theory calculations, the authors have achieved unprecedented fast hydrogen evolution kinetics, approaching that of Pt. Specifically, the Ni0.33Co0.67Se2 solid solutions show a low overpotential of 65 mV at −10 mV cm−2, with onset potential of mere 18 mV, an impressive small Tafel slope of 35 mV dec−1, and a large exchange current density of 184 µA cm−2 in acidic electrolyte. Further, it is shown that the as‐prepared Ni0.33Co0.67Se2 solid solution not only works very well in acidic electrolyte but also delivers exceptional hydrogen evolution reaction (HER) performance in alkaline media. The outstanding HER performance makes this solid solution a promising candidate for mass hydrogen production.

Heterostructures Composed of N‐Doped Carbon Nanotubes Encapsulating Cobalt and β‐Mo2C Nanoparticles as Bifunctional Electrodes for Water Splitting

“…High durability is an important criterion for an efficient electrocatalyst. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] To unveil the electronic interactions between b-Mo 2 C, Co, and N-CNTs,w es ystematically performed and compared DFT calculations on the adsorption free energy of H* (DG H* represents an adsorption site) of several models,i ncluding CNTs,N -CNTs,C o@N-CNTs,M o 2 C@N-CNTs,a nd Co/b-Mo 2 C@N-CNTs,d uring the HER (see Figure S12). Accelerated LSV was also conducted continuously for 1000 cycles,and the overpotential of Co/b-Mo 2 C@N-CNTs only increased by about 13 mV at j 10 (see Figure S11).…”

“…Furthermore,u pon encapsulating Mo 2 Cw ithin N-CNTs,t he DG H* value was effectively tuned, owing to the improved H*-chemisorption strength, which is promoted by the interfacial Mo-N coupling. [27][28][29][30][31][32][33][34][35][36][37] To better understand the higher OER activity of the Co/b-Mo 2 C@N-CNTs,w ei nvestigated the detailed OER mechanism using DFT calculations (Figure 4e,f). [23,36] Thee lectrocatalytic OER performance of the catalysts was also evaluated in 1.0 m KOH.…”

Active Site Identification and Evaluation Criteria of In Situ Grown CoTe and NiTe Nanoarrays for Hydrogen Evolution and Oxygen Evolution Reactions

“…At present, the state-of-the-art catalysts will effectively improve the performance of electrocatalytic reactions (such as OER, HER, and ORR). [15,30] Thus, CoTe or NiTe would be considered as an excellent candidate for overall water splitting. However, it is still lack of the pioneering study of TMT as bifunctional electrocatalysts for overall water splitting, because TMT may be thermodynamically unstable under the aqueous and strongly oxidative environments of OER and easily oxidized to the corresponding metal oxides/hydroxides, [31] and the reaction mechanism of TMT for overall water splitting is also unknown or unclear.…”

Strong Electronic Interaction in Dual‐Cation‐Incorporated NiSe2 Nanosheets with Lattice Distortion for Highly Efficient Overall Water Splitting

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focuses on exploration of efficient electrocatalysts that can overcome the sluggish kinetics and accelerate the evolution rates of H 2 and O 2 at low overpotentials. [11,12] In this content, the development of bifunctional catalysts which are highly active for both HER and OER in the same medium is highly desirable for overall water splitting.Accordingly, great efforts have been paid to developing bifunctional electrocatalysts based on transition metal nanomaterials and their derivatives, including metal oxides or hydroxides, [13,14] metal chalcogenides, [15][16][17] metal nitrides, [18,19] and metal phosphides. However, most of the recently developed HER and OER catalysts work in either acidic or alkaline medium.

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