Composition-Dependent Catalytic Activities of Noble-Metal-Free NiS/Ni₃S₄ for Hydrogen Evolution Reaction

Abstract

The development of efficient noble-metal-free hydrogen evolution catalysts is quite appealing with the aim of providing cost-competitive hydrogen.Herein, nickel sulfides (NiS x ) with tunable NiS/Ni 3 S 4 molar ratios were synthesized via a simple hydrothermal method. Detailed electrochemical studies under neutral conditions indicated that the electrocatalytic property of NiS x catalysts was determined by the composition. Notably, the NiS x sample with the NiS/Ni 3 S 4 molar ratio of 1.0 exhibited the lowest overpotential and charge-transfer resistance. As analyzed from the Tafel plots, the rate determining step of NiS x catalysts for hydrogen generation was the Volmer step, in which the proton adsorption played a key role.Theoretical calculation revealed that NiS and Ni 3 S 4 exhibited the metallic behaviors with different work functions. Consequently, the NiS x sample with the NiS/Ni 3 S 4 molar ratio of 1.0 owned the most adsorbed protons, which led to the highest electrocatalytic property. Meanwhile, NiS x was demonstrated to be efficient cocatalysts to promote photocatalytic hydrogen generation. NiS x /CdS with the S 4 molar ratio of 1.0 showed the best photocatalytic activity with the apparent quantum efficiency of 56.5% at 420 nm. This result was in good agreement with the electrocatalytic activities of NiS x samples, indicating the intrinsic property for efficient hydrogen generation.

Flexible Molecular Precursors for Selective Decomposition to Nickel Sulfide or Nickel Phosphide for Water Splitting and Supercapacitance

“…Comparatively, the nickel‐rich phase (Ni 2 P) is a suitable bifunctional material and has better efficiency in both energy storage and energy generation applications, than the Ni 5 P 4 phase. Qin et al . have provided composition‐dependent catalytic activities of NiS/Ni 3 S 4 for the hydrogen evolution reaction.…”

Sulfur‐Rich Colloidal Nickel Sulfides as Bifunctional Catalyst for All‐Solid‐State, Flexible and Rechargeable Zn‐Air Batteries

“…DFT study suggests that the sulfur‐rich phase NiS x ( i. e . Ni 3 S 4 and NiS 2 ) have their Fermi level within the nickel d band, an indication of their metallic behavior ,. In addition, the higher electron density of sulfur ions are ready to supply electrons in ORR, enabling more pronounced ORR activity enhancement compared to their nickel‐rich counterparts .…”

“…[4,6,15,17,19] DFT study suggests that the sulfur-rich phase NiS x (i. e. Ni 3 S 4 and NiS 2 ) have their Fermi level within the nickel d band, an indication of their metallic behavior. [26,27] In addition, the higher electron density of sulfur ions are ready to supply electrons in ORR, enabling more pronounced ORR activity enhancement compared to their nickel-rich counterparts. [28] With the good conductivity and stability, these sulfur-rich NiS x (e. g. Ni 3 S 4 and NiS 2 ) are anticipated to possess good catalytic activities toward both ORR and OER.…”

Novel Cu3P/g-C3N4 p-n heterojunction photocatalysts for solar hydrogen generation

“…7a, the Nyquist impedance plots for the electrodes could be fitted to an equivalent circuit (the inset) consisting of the series resistance (R s ), charge transfer resistance from the electrode to the electrolyte (R ct ), recombination resistance at the electrode interface (R rec ), and constant phase elements (CPE1 and CPE2). As summarized in Table S2, the values of R ct and R rec for Cu 3 P/g-C 3 N 4 were lower than those of g-C 3 N 4 , indicating that the Cu 3 P/g-C 3 N 4 had efficient charge- transfer behavior at the photocatalyst/solution interface [16,39]. The transient photocurrent responses of g-C 3 N 4 and Cu 3 P/g-C 3 N 4 were also investigated to examine their photoelectrochemical properties.…”