The Importance of Ligand Selection on the Formation of Metal Phosphonate-Derived CoMoP and CoMoP₂ Nanoparticles for Catalytic Hydrogen Evolution

Abstract

Coordination polymers (CPs) and metal–organic frameworks (MOFs) have emerged as versatile precursors for transition-metal phosphides catalysts. However, the controlled synthesis of CPs-derived bimetallic phosphides remains a challenge, as mixtures of various phosphide phases are often formed. Here, it is shown that controlling the formation of pure CoMoP and CoMoP2 nanoparticles requires a careful choice of the ligands used to construct the precursors based on the chemical properties of the metals. In particular, the nature and number of the coordination moieties of the ligand play key roles. CoMoP and CoMoP2 particles coated with N-doped carbon were derived from phosphonate-based CPs and compared as hydrogen evolution reaction (HER) electrocatalysts in acidic medium. CoMoP2 is more active and shows a turnover frequency (TOF) of 0.9 s–1 compared to 0.4 s–1 for CoMoP. The higher intrinsic activity of the CoMoP2 catalytic sites correlates with the differences in the electronic structure of the materials, with a larger charge transfer from the molybdenum to the phosphorus found for CoMoP2.

Dual Doping of MoP with M(Mn,Fe) and S to Achieve High Hydrogen Evolution Reaction Activity in Both Acidic and Alkaline Media

“…Metal phosphonates were chosen as precursors to benefit from the homogeneous distribution of the metals across the phosphonate network, which can promote a homogeneous distribution of the dopants after pyrolysis. [7,29] The effect of each dopant on the chemical, physical and electrochemical properties of MoP was first studied separately. The optimum amounts of dopants were then selected to design the dual-doped catalysts, which were subsequently investigated in depth.…”

“…[2,6] Transition-metal phosphides (TMPs) are a promising alternative to Pt, owing to their high HER activity in acid electrolytes, high conductivity and facile synthesis routes. [7][8][9][10] Molybdenum phosphide (MoP) has recently been the focus of intense investigations as a HER catalyst. [11,12] However, its activity in acidic media is still inferior to that of the Pt/C benchmark, and it is unsatisfactorily low in alkaline media.…”

Design and operando/in situ characterization of precious‐metal‐free electrocatalysts for alkaline water splitting

“…For instance, Xu et al 41 reported a series of metal phosphidesbased pre-catalysts by phosphidation process with different metal components (M = Fe, Co, Ni). The OER 42,67,[109][110][111][112] Metal phosphates have emerged as promising electrocatalysts owing to their structural stability. Previous studies indicate that phosphates group can facilitate the oxidation of metal atoms and act as proton acceptors to make the catalysts more favorable for water adsorption and oxidation.…”

“…The OER activities followed the order of FeCoNiP > CoNiP > FeNiP > FeCoP > CoP, where the intrinsic OER activity was related to the number of transition metal species. Besides, some dual‐doped metal phosphide catalysts such as Fe‐doped CoP, Co 2 P‐Ni 2 P, Fe‐doped Ni 2 P, Mo‐doped Ni 2 P, and NiCoP have been reported as bifunctional catalysts with exceptional OER and HER activity 42,67,109‐112 …”

Nanoporous Metal Phosphonate Hybrid Materials as a Novel Platform for Emerging Applications: A Critical Review

“…[147,[148][149][150] Porous metal phosphonate hybrids have been widely used as highly promising materials in numerous energy-storage reactions (e.g., Li-ion battery, fuel cells, and supercapacitors). [151][152][153][154][155] Porous metal phosphonate electrodes have the following remarkable properties: i) the predefined molecular redox functional groups can be flexibly integrated into pore walls or on the surface to control the redox potential; ii) the well-structured nanopores facilitate the intercalation/deintercalation of electrolyte ions;…”