High‐Temperature Nitridation Induced Carbon Nanotubes@NiFe‐Layered‐Double‐Hydroxide Nanosheets Taking as an Oxygen Evolution Reaction Electrocatalyst for CO₂ Electroreduction

Abstract

The electrochemical converting CO 2 into valuable fuels or chemicals and water splitting to produce hydrogen have become effective strategies to solve the energy crisis. [2] However, both the oxygen evolution reaction (OER) of water splitting to produce hydrogen and the cathode of electrochemical carbon dioxide reduction reaction (CO 2 RR) are multielectron transfer processes, which face a high reaction energy barrier. [3] Thus, it is necessary to develop a highly efficient catalyst to reduce the overpotential of OER and improve the activity and selectivity of CO 2 RR. [4] Currently, most of the catalysts for OER and CO 2 RR are noble metal-based catalysts, such as RuO 2 (for OER) and Au (for CO 2 RR). [5] However, noble metals have a low storage capacity on earth and high cost, so their widespread use on scale-up deployment is severely restricted. [6] Now it is critical to design low-cost and earth-abundant catalysts to replace the noble metal-based electrocatalysts. [7] Recently, layered double hydroxides (LDH) as one of the non-noble metals have been found as efficient OER catalysts because of their unique 2D lamellar structures. [8] For example, NiFe-LDH, [9] CoFe-LDH, [10] and NiV-LDH [11] are well-proven as excellent OER electrocatalysts under alkaline conditions. Unfortunately, the widespread application of LDH in OER is still unsatisfactory, mainly caused by the following two reasons. On the one hand, because the active sites of Bulk LDH are not fully exposed. [12] To solve this problem, liquid-exfoliation [13] and dry-exfoliation [10] of Bulk LDH have been systematically developed to expose more active sits. On the other hand, LDH has a low electron transfer efficiency in catalytic process. Combining LDH with conductive materials is a very effective way to improve the conductivity of LDH, such as carbon nanotubes (CNT), [14] graphene, [13,15] carbon quantum dots, [12] and other alkali corrosion-resistant carbon materials. [16] Over the past few years, researchers have also prepared various catalysts for CO 2 RR, such as non-metal elements (e. g., N, P, and S) doped carbon materials, [17] metal alloys, [18] and mental anchored on N doped carbon support (M-N-C). [19] Among them, the M-N-C has sparked considerable interest as CO 2 RR electrocatalysts,

NiFe-CN catalysts derived from the solid-phase exfoliation of NiFe-layered double hydroxide for CO2 electroreduction

“…Polyhydroxy materials (SPEM) were used for the exfoliation of NiFe-LDH. 25,52,53 First, NiFe-LDH powder (0.3 g) was added to ethanol, and the mixture was sonicated for 1 h. SPEM (29.7 g) was added to a mixing roller (XSS-300); then, the homodispersed mixture was added slowly. By adjusting the shearing speed, temperature, and solid-phase exfoliating process time, the NiFe-LDH was completely exfoliated into a single layer (denoted as NiFe-LDH-1), and the exfoliation efficiency of NiFe-LDH was 1 wt%.…”

“…N, 20,21 S, 22 F, 23 and P 24 doped carbon supports), common metal alloys ( e.g. Ni–Fe alloy/CNTs, 25 Cu–Sn alloy 26 ), metallic oxides (In 2 O 3 , 27 CuO, 28 ZnO, 29 and g-C 3 N 4 /Cu 2 O–FeO 30 ), and transition metal anchored on N-doped C materials (M-N-C; M = Fe, 31–33 Co, 34,35 Ni, 36–38 Mn, 39 Cu, 40 etc. ).…”

“…However, due to the tight-layered structure of LDHs, the metal elements gather together closely, which could form many alloys after pyrolysis. Solid-phase exfoliation based on polyhydroxy materials could exfoliate LDHs to a single layer, 25,52,53 which could help disperse the metal elements evenly.…”

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

“…After Er doping, the contact angle of sample is decreased from 21.5° to 17.8° (Figure S18, Supporting Information), indicating high hydrophilicity of Er-NiFe-LDH@NF, which is beneficial to improving the mass transfer between the electrolyte and the catalyst, thus accelerating the release of the gas bubbles generated during OER. [66,67]…”

Large‐Scale Synthesis of Spinel NixMn3‐xO4 Solid Solution Immobilized with Iridium Single Atoms for Efficient Alkaline Seawater Electrolysis

“…[27][28][29][30] The up-to-date seawater electrocatalysts also basically follow those in water electrolyzers, whereas few can meet the industrially mandated overpotential of 300 mV at 500 mA cm -2 with a cell voltage of below 1.60 V. Besides, apart from the prerequisite OER efficiency and stability, industrial seawater electrolyzer also require the electrocatalysts that can be easily scaled up, which is hardly achieved by template-based synthesis or exfoliation process. [31,32] Therefore, developing innovative seawater electrocatalysts with efficient OER activity and high selectivity, and mass-productive characteristics is of great necessity.…”