Atomic Modulation of Single Dispersed Ir Species on Self-Supported NiFe Layered Double Hydroxides for Efficient Electrocatalytic Overall Water Splitting

Abstract

Electrocatalytic overall water splitting is a promising approach for hydrogen production, and the rational design of the catalyst on the atomic level is critical for decreasing the energy barrier in both hydrogen and oxygen evolution reactions (HER/OER). Herein, we report an NiIr single atom alloy loaded NiFe-LDH (NiIrSAA-NiFe-LDH) and Ir single atom loaded NiFe-LDH (IrSAC-NiFe-LDH) for overall water splitting. The Ir single atoms are found via EXAFS fitting and DFT calculations to be located on the top of Fe3+ with Ir–O6 coordination on IrSAC-NiFe-LDH. The as-prepared NiIrSAA-NiFe-LDH presents an overpotential of 28.5 mV at 10 mA cm–2 in the HER and IrSAC-NiFe-LDH exhibits an overpotential of 194 mV at 10 mA cm–2 in the OER, respectively. Moreover, the electrolyzer assembled by NiIrSAA-NiFe-LDH and IrSAC-NiFe-LDH presents a low cell voltage of 1.49 V at 10 mA cm–2 and a long-term stability of over 120 h at 200 mA cm–2 in overall water splitting with an estimated cost of US $1.12 per kilogram of H2, meeting the target raised by the US Department of Energy (<US $2 kgH2 –1). Such high HER activity for NiIrSAA-NiFe-LDH can be attributed to the strong electronic interaction between Ni and Ir single atoms in NiIrSAA, resulting in an optimized hydrogen adsorption energy (ΔG H* = −0.17 eV). And the Ir single atoms modify the electronic structures of the adjacent Ni2+ in NiFe-LDH, which reduces the energy barrier of the O2 emission, thus enhancing the OER performance.

Enhancing Electrocatalytic Water Oxidation of NiFe-LDH Nanosheets via Bismuth-Induced Electronic Structure Engineering

“…Except for two obvious diffraction peaks of the nickel foam substrate at about 2θ = 44.5 and 51.9° (JCPDS 70-1849), the other four diffraction peaks at 2θ = 33.5, 34.4, 38.8, and 60.1° correspond to the (101), (012), (015), and (110) planes of NiFe LDH (JCPDS no. 40-0215) . No obvious Bi or BiO x diffraction peaks were found in the XRD patterns, indicating that Bi did not form individual compounds.…”

“…40-0215). 47 No obvious Bi or BiO x diffraction peaks were found in the XRD patterns, indicating that Bi did not form individual compounds. XPS was conducted to examine the surface element valence and electronic structure of Bi 0.2 NiFe LDH.…”

Design Principles of Single‐Atom Catalysts for Oxygen Evolution Reaction: From Targeted Structures to Active Sites

“…Majumdar et al [112] obtained homogeneous growth of mixed oxide/hydroxide nanosheets (MoO 3 /Ni-Co(OH) 2 ) of molybdenum and nickel/cobalt on nickel foam by hydrothermal method, so that they were successfully transformed into homogeneous MoSe 2 @NiCo 2 Se 4 heterostructures by selenization, and the porous structures induced by thin nanosheets with homogeneous surfaces were transformed into hierarchical structures by selenization. Later, Ir SAC (Ir-MoSe 2 @NiCo 2 Se Hu et al [113] prepared Ir SAC -NiFe-LDH by conventional hydrothermal method by impregnating NiFe-LDH precursor in Ir solution. NiIr SAA -NiFe-LDH loaded with NiIr single alloys was obtained by reduction with NaBH 4 .The contents of Ir in both of them are respectively 8.47% and 8.31%, respectively.…”

“…NiRu0.08-MOF Reproduced with permission [98]. Copyright 2023, John Wiley & Sons, Inc. IrSAC-NiFe-LDH Reproduced with permission [113]. Copyright 2023, American Chemical Society.…”

“…f) Gibbs free energy diagrams for OER at U = 1.23 V on NiI rSAA -NiFe-LDH, Ir SAC -NiFe-LDH, and NiFe-LDH. (Reproduced with permission [113]. Copyright 2023, American Chemical Society.)…”