Improving the Oxygen Evolution Activity of Layered Double‐Hydroxide via Erbium‐Induced Electronic Engineering

Abstract

water-splitting in industrial applications, OER catalysts with a low overpotential, high activity, and long-term stability are urgently needed to be discovered. [7][8][9][10] So far, the state-of-the-art OER electrocatalysts are noble-metal Ir or Ru oxides, [11,12] while some intrinsic drawbacks including high cost, scarcity, and poor stability restrict their large-scale applications. To this end, reducing the use of Ir and Ru-based materials or developing alternatives is attractive and acceptable.The cut-price transition-metal-based catalysts including oxides, [13][14][15] hydroxides, [16][17][18] sulfides, [19][20] selenides, [21][22] and nitrides [23,24] have been investigated extensively as alternatives in OER. Among them, layered double hydroxide (LDH) has been acknowledged as one of the potential OER catalysts because of the unique electronic coupling between metal species that greatly optimizes the rate-determining step between *OOH and *OH. [25][26][27][28][29] As a typical example of NiFe-LDH, the incorporation of Fe influences the redox property of Ni, which makes a positive shift in the potential of Ni(OH) 2 /NiOOH redox and a decrease in the oxidation state of Ni sites, leading to a high OER activity of Ni sites. [30][31][32] However, the presence of superfluous Fe species may generate detrimental lattice distortion, which affects the effective orbital coupling in NiFe-LDH, thus reducing the electronic conductivity and restraining the OER activity. [33][34] To break through the current bottleneck, it is needed to simultaneously regulate the electronic structure and tolerate the detrimental lattice distortion. [35] The construction of a more flexible Layered double-hydroxide (LDH) has been considered an important class of electrocatalysts for the oxygen evolution reaction (OER), but the adsorptiondesorption behaviors of oxygen intermediates on its surface still remain unsatisfactory. Apart from transition-metal doping to solve this electrocatalytic problem of LDH, rare-earth (RE) species have sprung up as emerging dopants owing to their unique 4f valence-electronic configurations. Herein, the Er is chosen as a RE model to improve OER activity of LDH via constructing nickel foam supported Er-doped NiFe-LDH catalyst (Er-NiFe-LDH@NF). The optimal Er-NiFe-LDH@NF exhibits a low overpotential (191 mV at 10 mA cm −2 ), high turnover frequency (0.588 s −1 ), and low activation energy (36.03 kJ mol −1 ), which are superior to Er-free sample. Electrochemical in situ Raman spectra reveal the facilitated transition of Ni-OH into Ni-OOH for promoted OER kinetics through the Er doping effect. Theoretical calculations demonstrate that the introduction of Er facilitates the spin crossover of valence electrons by optimizing the d band center of NiFe-LDH, which leads to the G O -G HO closer to the optimal activity of the kinetic OER volcano by balancing the bonding strength of *O and *OH. Moreover, the Er-NiFe-LDH@NF presents high practicability in electrochemical water-splitting devices with a low driving potential of ...

Reinforcing CoO Covalency via Ce(4f)─O(2p)─Co(3d) Gradient Orbital Coupling for High‐Efficiency Oxygen Evolution

“…Owing to the preferred ionic property of the RE-O bond, it is speculated that the construction of the RE-O-TM framework may realize the conservation of TM─O covalency, while electron removal occurs from the higher RE-4f states. Currently, some RE elements such as Ce, [28][29][30] La, [31][32][33] Er, [34][35][36] and Nd [37,38] have been introduced into a number of electrocatalyst systems to enhance OER. However, the catalytic mechanism based on the f-orbital-induced M-O covalency modulation has rarely been studied and the identification of the active sites of RE-TMOs toward OER is limited.…”

Hierarchical porous NiFe-P@NC as an efficient electrocatalyst for alkaline hydrogen production and seawater electrolysis at high current density

“…5d, for the in situ Raman spectra during the OER, the two characteristic peaks of Ni-O vibrations observed at 457 cm −1 and 538 cm −1 when the applied voltage reached 1.48 V indicated that the true active site of the OER should be the corresponding hydroxide. 78 Meanwhile, NiFe-P@NC showed similar trends in electrocatalytic activity towards the HER, which required a low of 153 and 264 mV to reach 100 and 500 mA cm −2 , respectively (Fig. 5e and f ).…”

Hierarchically porous Ni foam-supported Co and Sn doped Ni3S2nanosheets for oxygen evolution reaction electrocatalysts

“…S7a †). 67,68 Cell performance tests were conducted at a temperature of 80 °C (55 °C) and a ow rate of 30 wt% (1 M) KOH solution equal to 200 ccm (300 ccm).…”