Oxygen Vacancy‐Rich La_0.5Sr_1.5Ni_0.9Cu_0.1O_4–δ as a High‐Performance Bifunctional Catalyst for Symmetric Ammonia Electrolyzer

Abstract

In this study, strontium and copper dual-doped La 2 NiO 4 annealed in Ar (La 0.5 Sr 1.5 Ni 0.9 Cu 0.1 O 4-δ -Ar, LSNC-Ar) with K 2 NiF 4 structure is strategically designed as an ammonia oxidation reaction (AOR) and hydrogen evolution reaction (HER) bifunctional catalyst for high-efficiency ammonia electrolysis. The selective substitution of lanthanum with high content strontium improves the electronic conductivity and increases the oxygen vacancy concentration. Doping of Cu into the B-site of the perovskite induces a synergistic interplay of Ni and Cu, leading to excellent AOR activity. Due to the excellent AOR and HER activity of doped La 2 NiO 4 , a symmetric ammonia electrolyzer based on LSNC-Ar (SAE-LSNC-Ar) is assembled and investigated for the removal of ammonia. In addition, the performance of the SAE is comparable to the ammonia electrolyzer based on a PtIr/C anode and Pt/C cathode at low voltage. This is the first report using an oxide with the K 2 NiF 4 structure as an efficient AOR catalyst. The assembled SAE-LSNC-Ar shows ≈95% ammonia removal efficiency in real landfill leachate, which is the highest among electrochemical removal of ammonia in landfill leachate. This study paves an attractive route to explore materials with the K 2 NiF 4 structure as highly efficient AOR/HER bifunctional catalysts for the electrolysis of ammonia.

A symmetric direct ammonia fuel cell using ternary NiCuFe alloy embedded in a carbon network as electrodes

“…40 In the past five years, a wide variety of materials based on non-precious 3d transition metals, such as Ni, Cu, Co, Fe, have gained rapid recognition over Pt as an attempt to increase the practicality of AOR catalysts by lowering the cost. 11,[41][42][43][44][45][46][47] Amongst these metals, experimental studies have reported that Ni-based materials are the most promising catalysts with respect to AOR activity and high selectivity towards N 2 in low to intermediate temperature ranges. 45,48,49 However, compared to Pt, the d band center of the Ni metal is relatively wide, which means that Ni binds less strongly to the reactants and does not adsorb the reactants as efficiently as Pt.…”

“…5,10 Ammonia can be dissolved in water to create a solution with a solubility limit of around 35 wt% that can be kept in a glass container without the need for any extra equipment. 2,11 In addition, it also can be readily liquified by increasing pressure to ~10 bar at room temperature or by cooling to -33 °C at atmospheric pressure, which is much easier than that of hydrogen. 5 Except for liquid storage, ammonia is found to be stored as a solid in metal-amine complexes.…”

Constructing Heteroatom-Doped Transition-Metal Sulfide Heterostructures for Hydrogen Evolution Reaction

“…In addition, the increased pH of electrolytes will reduce the concentration of H + and slow down the formation of M*–H ads . However, the much higher concentration of KOH will also provide a fast mass transfer and charge transport to reduce the energy demands for the HER in the alkaline system. , …”

“…41 However, the much higher concentration of KOH will also provide a fast mass transfer and charge transport to reduce the energy demands for the HER in the alkaline system. 42,43 Compared the above electrochemical parameters with the structural characterizations, the contradiction between S BET and EASA can be attributed to the following reasons: the homogeneously distributed precursors and weak interactions of HAs@MoS 2 /Ce 2 S 3 deliver outstanding electroactive sites by reducing the aggregation; 23,37 the heterostructures of HAs@ MoS 2 /Ce 2 S 3 also provide numerous high-active catalytic sites by fabricating the edge S−M−S sites of MoS 2 , 2,5,10 the undercoordinated surface cations, and the ligand (S adsorbing H atoms to form S−H bands) number of Ce 2 S 3 . 11,12 The changes of the catalyst (HAs@MoS 2 /Ce 2 S 3 /CC) between and after the electrochemical catalysis have been further investigated.…”

A/B-Site Management Strategy to Boost Electrocatalytic Overall Water Splitting on Perovskite Oxides in an Alkaline Medium

“…An X-ray photoelectron spectroscopy analyzer was used to analyze the valence state and composition of the elements of the material, and the spectra obtained were corrected by the C 1s spectral line with a binding energy of 284.8 eV (ESCALAB 250Xi, Thermo). Iodometric titration was used to test the oxygen vacancy content of perovskite oxides . Excess KI (∼2 g) and 50 mg perovskite oxides were dissolved in 100 mL of 1 M HCl.…”