Function of Internal and External Fe in a Ni-Based Precatalyst System Toward Oxygen Evolution Reaction

Abstract

It is well known that the “iron” impurity will influence the oxygen evolution reaction (OER) in an alkaline electrolyte, especially for the Ni-based electrocatalyst. Many research studies have investigated the function of Fe in the OER active phase, such as M(OH)2/MOOH (M = Ni and/or Fe), while, surprisingly, very few studies have examined the function of Fe in the “precatalyst” system. Accordingly, in this work, the Ni3–x Fe x P (x = 0, 0.5, 1) series as an Ni-based precatalyst was employed to inspect the function of internal and external Fe in the Ni-based precatalyst system. It was realized that the sample with internal Fe (i.e., Ni2.5Fe0.5P and Ni2FeP) exhibits efficient OER activity compared to that of the Fe-free one (i.e., Ni3P) owing to the large amount of active M(OH)2/MOOH formed on the surface. This indicates that the internal Fe in the present system may have the ability to facilitate the phase transformation; it was later rationalized from electronic structural calculations that the d band center of the internal Fe (middle transition metal) and Ni (late transition metal) holds the key for this observation. Adding excessive ferrous chloride tetrahydrate (FeCl2·4H2O) as the external Fe in the electrolyte will greatly improve the OER performances for Ni3P; nevertheless, that the OER activity of Ni2FeP is still much superior than that of Ni3P corroborates the fact that the Fe impurity is not the only reason for the elevated OER activity of Ni2FeP and that internal Fe is also critical to the phase transformation as well as OER performance.

Alkali Containing Layered Metal Oxides as Catalysts for the Oxygen Evolution Reaction

“…Many studies have indeed shown that Fedoped nickel oxides are promising electrocatalysts for the OER. [70][71][72][73][74] Similar to Fe-doped nickel oxides, the effect of Fedoping in Li-layered metal oxides as electrocatalysts for the OER has been investigated. A series of Co-based oxides, LiCo 1-x M x O 2 (M = Ni, Fe and Mn) was also investigated by Lu et al using the same preparation methods as for LiCoO 2 and Li 0.5 CoO 2 .…”

Ultrafine IrRu Nanoparticles toward Efficient Oxygen Evolution Reaction in Acidic Media

“…where A geo is the geometric area of the glassy carbon electrode, which equals 0.19625 cm 2 . The specific current density per ECSA (j s ) was calculated as shown in eq 3:…”

“…Water electrolysis has been regarded as one of the most promising strategies for widespread hydrogen production. PEMWEs and alkaline water electrolyzers (AWEs) represent two major hydrogen production technologies. − PEMWEs can produce much purer hydrogen at a larger current density and a higher energy efficiency as compared to AWEs. However, a grand challenge of PEMWEs is the slow kinetics of acidic OER, which involves multiple electron transfer and a high reaction energy barrier .…”

Strong coupling effect induced surface reconstruction of CeF3–Ni3N to form CeF3–NiOOH for the oxygen evolution reaction

“…[8][9][10][11] Therefore, it is imperative to use more affordable and abundant non-noble metal compounds as catalysts for the electrocatalytic OER. In this regard, earth-abundant metals (Ni, Co, Fe, and Cu) [12][13][14][15] and their associated suldes, [16][17][18][19] oxides, [20][21][22] phosphides, [23][24][25] selenides, [26][27][28] and nitrides [29][30][31] are being aggressively investigated as electrocatalysts for the OER. Out of these, transition-metal nitrides exhibit exceptional OER performances due to their distinct electronic structure and unique physical and chemical characteristics.…”