Electrocatalytic Synthesis of Ammonia Using a 2D Ti₃C₂ MXene Loaded with Copper Nanoparticles

Abstract

As an energy‐saving and environmentally friendly ammonia synthesis method, electrocatalytic nitrogen reduction reaction (NRR) has received a great deal of attention. There is thus an urgent need to find high‐efficiency electrocatalysts for the NRR. In this work, a Cu/Ti3C2 composite catalyst was prepared and demonstrated excellent selectivity under environmental conditions, which could efficiently convert N2 into NH3 electrochemically. In 0.1 M KOH, Cu/Ti3C2 can achieve a high Faradaic efficiency of 7.31 % and a high NH3 production rate of 3.04 μmol h−1 cm−2 at −0.5 V vs. RHE. Moreover, the material also exhibits superior electrochemical stability and durability. At the same time, density functional theory (DFT) shows that, compared with Ti3C2, Cu/Ti3C2 exhibits a wider conduction and valence band and a larger Fermi level, thus indicating that Cu plays a vital role in the enhancement of the catalytic activity and conductivity of Ti3C2‐based materials. This work provides a feasible strategy for designing high‐efficiency MXene‐based NRR electrocatalysts.

Recent advances in material design and reactor engineering for electrocatalytic ambient nitrogen fixation

“…The advanced catalysts for efficiently promoting the N 2 fixation performance are discussed in this section (Table 1). 82–146 Given that the reaction potential range of the NRR overlaps with that of the HER and it has a higher kinetic barrier in comparison, most of the catalysts reported thus far are dominated by the competitive HER reaction under the reaction conditions. Consequently, the FE for the production of NH 3 is often less than 20% and the NH 3 yield is also 2–3 orders of magnitude lower than that of industrial catalysts.…”

Two‐Dimensional MXene Supported Bismuth for Efficient Electrocatalytic Nitrogen Reduction

“…As shown from the O 1s profile in Figure 3b, the peaks at 529.6 eV, 530.3 eV, and 530.9 eV are respectively assigned to the TiO 2 , Ti−O−Ti, and C−Ti−O x bonds. Figure 3c displayed the XPS spectrum of the Ti 2p+Bi 4d region, which can be divided into 8 sub‐peaks, corresponding to Ti−C (454.5 and 458.2 eV), [40–41] Ti−O (455.5 and 460.4 eV), Ti−O−Ti (461.3 eV), [40] TiO 2 2p 1/2 (464.3 eV), [42] and Bi 4d 3/2 (463.1 and 466.2 eV), respectively. Moreover, the high‐resolution Bi 4 f spectrum of the Bi@Ti 3 C 2 in Figure 3d has two peaks at 158.95 eV and 164.3 eV, which are assigned to Bi 4f 7/2 and Bi 4f 5/2 , respectively [43] .…”

Ru and Fe Alloying on a Two‐Dimensional MXene Support for Enhanced Electrochemical Synthesis of Ammonia

“…The element valence state and structural composition of RuFe@MXene composite were further analyzed by X‐ray photoelectron spectroscopy (XPS), and all data were calibrated with 284.8 eV of C 1s. In the high‐resolution XPS spectrum of Ti 2p shown in Figure 3a, seven main peaks are shown, corresponding to Ti−C (454.44 eV), [50] Ti−O (455.26 eV), Ti 2 O 3 (457.72 eV), TiO 2 2p 3/2 (458.25 eV), [50] C−Ti−O (461.27 eV), [32] Ti 3+ (463 eV), [51] TiO 2 2p 1/2 (464.06 eV) [52] . As shown in Figure 3b, the high‐resolution O 1s is deconvoluted into five peaks positioned at 529.15 eV, 529.53 eV, [53] 530.2 eV, [54] 531.01 eV, and 532.12 eV, [30] corresponding to O−Ti−O, C−Ti‐(OH) x , Ti−O−Ti, RuO 2 , and TiO 2 , respectively.…”

“…The general formula of MXenes is M n+1 X n T x (n=1, 2 and 3), where M represents the transition metal (M=Ti, Sc, Zr, Hf, Ta, V, Mo, Cr), X is carbon, nitrogen or carbonitride, and T x represents the surface group, such as −O, −OH, or −F, etc [29–31] . Owing to its high specific surface area, high conductivity, good hydrophilic properties, and abundant surface chemical groups, it shows unique application prospects in the field of electrochemical NRR [32–38] . In addition, ruthenium (Ru) has been used in electrochemical NRR to produce ammonia, and both theory and experiment have proved that it has good NRR activity, which can improve the NH 3 yield and Faraday efficiency (FE) of the NRR process to a certain extent [39–41] .…”