Nickel Phosphides Fabricated through a Codeposition–Annealing Technique as Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution Reaction

Abstract

Water splitting will be one of the most strategic techniques in the upcoming hydrogen-based economy. In this context, the development of efficient and low-cost Pt-free electrocatalysts is crucial to make it economically viable. The present work proposes a low-cost and scalable methodology to produce electrocatalytic layers based on nickel phosphide for hydrogen evolution reaction. In particular, a nickel–phosphorus solid solution is electrolytically codeposited together with red phosphorus particles. This approach overcomes the compositional limit typical of electrodeposited Ni–P by providing a supplementary phosphorous source directly embedded in the layer and makes it possible to synthesize high-P phosphides such as Ni12P5 and Ni2P. The obtained composites are subjected to different annealing cycles to precipitate phosphides, evidencing a major influence of process conditions on the final phase composition. X-ray photoelectron spectroscopy reveals the presence of a phosphorus-depleted region in correspondence of the surface of the samples. Finally, layers are tested to assess their electrocatalytic performances, and the effects of annealing time and catalyst loading are investigated. Samples with an optimized content of Ni2P evidence the lowest overpotential values, with 224 mV at 10 mA/cm2, and good stability over time.

Nickel Phosphide Nanoparticles for Selective Hydrogenation of SO2 to H2S

“…Other authors examining Ni 2 P, Ni 12 P 5 , and Ni 5 P 4 have observed that there is no substantial or systematic change in the binding energies of these phosphides as a function of composition, in agreement with the results observed here. − The higher binding energy P 2p peak occurs at a binding energy of 133.6–134.3 eV. This peak corresponds to the oxidized surface of the nickel phosphide catalysts and can be attributed to Ni 3 (PO 4 ) 2 in accordance with other references. ,, The strongest Ni 2p 3/2 peak for all Ni catalyst samples occurs in a binding energy range of 856.8–857.3 eV. Cheong et al state that the small binding energy difference between Ni­(OH) 2 and Ni 3 (PO 4 ) 2 makes it difficult to distinguish between these two chemical states .…”

“…This peak corresponds to the oxidized surface of the nickel phosphide catalysts and can be attributed to Ni 3 (PO 4 ) 2 in accordance with other references. 58,61,62 The strongest Ni 2p 3/2 peak for all Ni catalyst samples occurs in a binding energy range of 856.8−857.3 eV. Cheong et al state that the small binding energy difference between Ni(OH) 2 and Ni 3 (PO 4 ) 2 makes it difficult to distinguish between these two chemical states.…”

Suitably Band‐aligned MOF‐Derived Ni2P/MnO2 Heterostructure with Ni(I) Coordination Surface Sites for Self‐Coupling of Aryl Halides to Biaryls

“…These peak positions for Ni in the literature have been assigned to the Ni δ+ . The consistent presence of this peak in the Ni 2 P XPS has been well associated with the Ni I [48–50] . Similarly, XPS confirms the presence of δ‐MnO 2 as evidenced by the peaks of 642.21 eV and 654.58 eV corresponding to 2p 3/2 and 2p 3/2 of Mn IV state as depicted in Figure 2d.…”

Ni2P Nanoparticles Embedded in Mesoporous SiO2 for Catalytic Hydrogenation of SO2 to Elemental S

“…This peak corresponds to the oxidized surface of Ni 2 P and can be attributed to Ni 3 (PO) 4 in accordance with other references. 7,23,24,26 The strongest Ni 2p 3/2 peak for all Ni 2 P and Ni catalyst samples occurs at binding energies between 856.7 and 857.2 eV. Cheong et al give a binding energy of 856.7 eV for Ni(OH) 2 and state that the small binding energy difference between Ni(OH) 2 and Ni 3 (PO) 4 makes it difficult to distinguish between these two chemical states.…”