Single Nanometer-Sized NiFe-Layered Double Hydroxides as Anode Catalyst in Anion Exchange Membrane Water Electrolysis Cell with Energy Conversion Efficiency of 74.7% at 1.0 A cm^–2

Abstract

We used a liquid phase reaction to synthesize a nickel (Ni) and iron (Fe)-containing layered double hydroxide (NiFe-LDH), having a lateral size less than 10 nm. A chelating agent introduced into the media was thought to increase the concentration of metal hydroxide nuclei and suppress excessive growth of the LDH crystal, resulting in the synthesis of nanometer-sized LDH. The NiFe-LDH catalyzed the oxygen evolution reaction (OER) at an overpotential of 247 mV and current of 10 mA cm–2, which is superior to the performance of conventional iridium oxide (IrO x ) catalysts. Notably, a membrane electrode assembly (MEA) for anion exchange membrane water electrolysis using NiFe-LDH as an anode catalyst exhibited an energy conversion efficiency of 74.7% for flowing 1.0 A cm–2 in 1 M KOH at 80 °C. This efficiency is the highest among MEAs implemented with non-noble metal-based catalysts reported to date and offers a viable replacement for IrO x anode catalysts.

Rapid Synthesis of Various Electrocatalysts on Ni Foam Using a Universal and Facile Induction Heating Method for Efficient Water Splitting

“…The value of Tafel slope indicated that the NiFe LDH/NF‐IH presented fast OER kinetics. [ 31 ] The EIS Nyquist plots in Figure S11 in the Supporting Information, electrochemically active surface area in Figure S12 in the Supporting Information, and long‐term stability tests in Figure 4f also confirmed that the NiFe LDH/NF‐IH synthesized by IH presented the highly efficient electrocatalytic OER activity. Moreover, after i – t testing, the morphology of NiFe LDH/NF‐IH nanosheets still retained (Figure S13, Supporting Information), showing the outstanding stability in structure.…”

High‐Efficiency Anion Exchange Membrane Water Electrolysis Employing Non‐Noble Metal Catalysts

“…[11] A record-low cell voltage of 1.59 V was obtained at 1.0 A cm −2 at 80 °C, but using a noblemetal catalyst for HER, and a non-noble-metal catalyst (NiFe LDH) for OER. [12] Here we report an AEM electrolyzer that operates at 1.57 V for 1.0 A cm −2 at 80 °C, the lowest for any catalytic stability of NiMo-NH 3 /H 2 catalyst was confirmed in a 20 h electrolysis at −0.1 V vs. RHE, where the current density showed negligible change ( Figure S8, Supporting Information).…”

“…[ 11 ] A record‐low cell voltage of 1.59 V was obtained at 1.0 A cm −2 at 80 °C, but using a noble‐metal catalyst for HER, and a non‐noble‐metal catalyst (NiFe LDH) for OER. [ 12 ] Here we report an AEM electrolyzer that operates at 1.57 V for 1.0 A cm −2 at 80 °C, the lowest for any AEM electrolyzer. Our electrocatalysts are based on the same base material, NiMo oxide.…”

“…As such, they are well suited for AEM electrolyzer applications. Until now, only a few OER catalysts [10,12,26,27] such as Cu 0.7 Co 2.3 O 4 , NiFe-LDH, NiFe 2 O 4 , CuCoO 3 and Co 3 O 4 , and a few HER catalysts [11,26,27] such as NiFeCo, Ni, and Ni/(CeO 2 -La 2 O 3 )/C have been applied in AEM electrolyzers (Table S6, Supporting Information). The performance of such systems remains modest.…”

A Review of the Use of Immobilized Ionic Liquids in the Electrochemical Conversion of CO2

“…The experimental results with the Sustainion ® -based system were a set of ionomers and membranes that were stable for at least 12,000 h at 60 • C in 1 M KOH, as shown in Figure 2. Presently, these membranes are being evaluated by multiple investigators [21][22][23][24][25][26][27][28][29]. This paper briefly reviews the results in the CO 2 conversion to CO as well as in the conversion to formic acid.…”