N‐doped Carbon‐coated Metal Sulfides/Phosphides Derived from Protic Salts for Oxygen Evolution Reaction

Abstract

Transition metal sulfides (TMSs) and transition metal phosphides (TMPs) have emerged as highly active catalysts for electrochemical applications. However, the present preparation methods for TMSs and TMPs are always complex and tedious. Herein, we developed a facile and effective strategy for synthesis of nitrogen (N)‐doped carbon‐coated TMSs or TMPs, which was realized by ball milling protic salts (p‐phenylenediamine bisulfate or p‐phenylenediamine biphosphate) and metal salts, followed by pyrolysis. A serious of TMSs and TMPs with well crystalline structures were obtained and witnessed by XRD analysis. Further electrocatalysis performance study in oxygen evolution reaction demonstrates that Ni‐modified MoS2/NC catalyst exhibited excellent activity, showing an overpotential of 261 mV at the current density of 10 mA cm−2 with a small Tafel slop of 53 mV dec−1. The satisfactory performance of Ni−MoS2/NC might be derived from the synergistic effect between Ni and MoS2 that led to enhanced charge transport capability and more efficient kinetics. This work not only provides a simple and general pathway to TMSs and TMPs‐based materials, but also enables excellent OER performance to be achieved.

A Review of Transition Metal Boride, Carbide, Pnictide, and Chalcogenide Water Oxidation Electrocatalysts

“…By combining metal salts, MoCl 5 and NiCl 2 , with the protic salt p -phenylenediamine bisulfate ([PDA]­[2HSO 4 ]), a precursor rich in S and N, via ball-milling and pyrolysis at 800 °C under nitrogen atmosphere, a N-doped carbon-coated Ni-Mo sulfide (Ni-MoS 2 /NC) was produced. Ni-MoS 2 /NC resulted because, at 800 °C, the protic salt transformed into a N-doped carbon shell, releasing S from its structure, which reacted with Mo to form MoS 2 , as confirmed by XPS results . Thus, the resulting material, Ni-MoS 2 /NC, consisted of a Ni-MoS 2 core covered by a N-doped carbon shell, which could serve as a protective layer against oxidation for the transition metal sulfide core under alkaline conditions at oxidizing potentials.…”

“…Here, hydrothermal sulfidation is one of the most utilized conversion techniques (refs 673, 683, 687, 688, 690, 766, 772, and 773). Regarding sulfur sources used in the sulfidation process for both one-step and two-step processes, the most frequently used are sodium sulfide (Na 794 There are, however, some unique synthetic cases for metal sulfide preparation that do not involve the sulfidation process: the precursor itself contains sulfur and can be transformed into the metal sulfide electrocatalyst upon annealing. 792 Regardless of whether the one-step or two-step process is used for the preparation of the metal sulfides, all the abovementioned synthetic steps involve some standard synthetic methods [i.e., hydrothermal method, solvothermal method, electrodeposition, MOF-derived method, and other less frequently used methods (e.g., chemical vapor deposition, anion exchange method, solid-state reaction, fast annealing method, and so on)].…”

“…Here, for the synthesis of metal sulfide-based electrocatalysts, the most commonly used starting materials are Ni foam, ,, Cu foam, and metal complexes/salts (i.e., central atoms/ions bonded to one/more ligands) (refs , , , , , , , and ), among which the metal complexes/salts are the most popular option. In the case of precursors, the most commonly used/prepared precursors reported in the literature were MOFs (refs , , , , and ), metal complexes/salts, ,, and metal oxides/hydroxides (refs , , , , , , , , and ). Among the above precursors, the metal oxides/hydroxides are the most popular precursors for transition metal sulfide synthesis.…”

“…Here, hydrothermal sulfidation is one of the most utilized conversion techniques (refs , , , , , , , and ). Regarding sulfur sources used in the sulfidation process for both one-step and two-step processes, the most frequently used are sodium sulfide (Na 2 S) (refs , , , , , and ), thioacetamide (C 2 H 5 NS) (refs , , , and ), sulfur powder (refs , , and ), thiourea (CH 4 N 2 S) (refs , , , and ), CS 2 gas, and [PDA]­[2HSO 4 ] (PDA: p -phenylene­diamine) . There are, however, some unique synthetic cases for metal sulfide preparation that do not involve the sulfidation process: the precursor itself contains sulfur and can be transformed into the metal sulfide electrocatalyst upon annealing …”

“…Schematic of Ni-MoS 2 /NC preparation and inset SEM image of the prepared electrocatalyst. Reproduced with permission from ref . Copyright 2019 Wiley.…”