Ligand and Anion Co‐Leaching Induced Complete Reconstruction of Polyoxomolybdate‐Organic Complex Oxygen‐Evolving Pre‐Catalysts

Abstract

The coordination compounds in the oxygen evolution reaction (OER) have been researched extensively. However, their poor durability (mostly < 100 h) and controversial reconstruction mechanism restrict their practical applications. Herein, a new‐type polyoxomolybdate‐organic complex (POMo) via wet‐chemistry synthesis with fixed coordination between metal centers (Ni2+ and [Mo8O26]4−) and 2‐Methylimidazole ligand is introduced. After introducing iron, a series of Fe‐doped Ni‐POMo with porous and amorphous structures are fabricated. These features accelerate the diffusion‐leaching processes of ligands and anions, resulting in rapid and complete phase reconstruction during alkaline OER. As a result, nickel‐iron (oxy)hydroxides with rich vacancies and poly‐/low‐crystalline features are in situ generated through dissolution‐redeposition, and serve as the OER‐active species. The optimized Fe0.052Ni‐POMo array pre‐catalyst has excellent activity and sustains ultrastable catalysis for 545 h. The complete reconstruction of POMo enables high catalytic durability (230 h) and stable active phase under realistic conditions (30 wt% KOH, 60.9 °C). Accordingly, the completely reconstructed catalysts with unique structures and ultrastable catalysis have the potential to be applied in industry.

Spherical Ni3S2/Fe‐NiPx Magic Cube with Ultrahigh Water/Seawater Oxidation Efficiency

“…The O-vacancies formed may be attributed to the rapid oxidative reconstruction process of the electrode material and play a positive role in the OER activity. [41] The XRD pattern (Figure S28, Supporting Information) still shows the characteristic diffraction peaks of Ni 3 S 2 , Ni 12 P 5 , and Ni 2 P, with a relative intensity reduction compared to the initial Ni 3 S 2 /Fe-NiP x /NF, which further proves the structural stability of Ni 3 S 2 /Fe-NiP x /NF at large current densities, manifesting that the reconstruction occurs only at the surface level. [40] Moreover, the Raman spectroscopy in Figure S29 (Supporting Information) further confirms the formation of Ni(Fe)OOH.…”

“…The O‐vacancies formed may be attributed to the rapid oxidative reconstruction process of the electrode material and play a positive role in the OER activity. [ 41 ]…”

Avoiding Pyrolysis and Calcination: Advances in the Benign Routes Leading to MOF‐Derived Electrocatalysts

“…To improve the OER performance of MOF‐derived electrocatalysts and to elucidate their structural conversion mechanisms, more studies have started to pay close attention to the completely reconstructed MOFs following alkaline hydrolysis [53,58] . Using a mixed Fe−MOFs@Ni−MOFs hybrid platform, Bu and co‐workers systematically investigated the active species and reaction mechanisms [55] .…”

“…Especially, carboxylate‐based MOFs are relatively fragile under strongly alkaline conditions (that OER entails), while OH − ions can cleave the coordination bonds holding the carboxylate linkers to the metal sites, resulting in the formation of metal hydroxides [51b,52] . Accordingly, some latest works have reported an alkaline hydrolysis strategy for delivering MOF‐derived OER electrocatalysts [51a,53] . As an example, Li and co‐workers developed a facile alkali‐etched method to obtain the defect‐rich ultrathin Ni‐MOF nanosheet array (D−Ni−MOF NSA) for OER [54] .…”

Direct Electrosynthesis of Selective Transition-Metal Chalcogenides as Functional Catalysts with a Tunable Activity for Efficient Water Electrolysis

“…The rapidly increasing global energy demands along with the demand for environmental protection and economic efficiency have triggered significant worldwide efforts toward the development of more efficient renewable energy technologies. , In this regard, water electrolysis, which is an eco-friendly water splitting process that produces environmentally benign hydrogen, has received considerable attention as one of the most promising ways for storing hydrogen owing to its high energy density, which serves as a green and carbon-neutral energy carrier. − For a long time, Pt and noble metal oxides such as RuO 2 and IrO 2 have been considered the most active and efficient electrocatalysts for cathode and anode reactions, respectively; however, their application is limited by scarcity and high cost. − Accordingly, in recent years, there have been enormous efforts to develop high-efficient, low-cost, and earth-abundant electrocatalysts as alternatives to Pt or noble metal-based oxides for successful large-scale commercialization of sustainable energy sources. − As a result, transition-metal-based compounds including oxides, nitrides, phosphides, and chalcogenides have shown significant progress in electrocatalyst performance comparable to their benchmark noble electrocatalysts as nonprecious and earth-abundant alternatives. − Among them, in particular, transition-metal chalcogenides (TMCs) have recently been proposed and demonstrated to be the most potential candidates because of their attractive features, including high electrical conductivity, energetically attractive atomic configuration, and d-band structure favorable to both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). − …”