Interfacial Polarization Triggered by Covalent‐Bonded MXene and Black Phosphorus for Enhanced Electrochemical Nitrate to Ammonia Conversion

Abstract

MXenes have recently emerged as a new class of electrocatalysts for diverse energy conversion reactions, but they are generally considered to be catalytically inert. Herein, a strategy of interfacial polarization is put forward to improve the catalytic activity of MXenes, with the construction of an interfacial structure consisting of black phosphorus (BP) nanoflakes and Nb2C MXene nanosheets for electrochemical nitrate reduction to ammonia as a proof of concept. The experimental and computational results reveal that a strong interfacial polarization is built between BP nanoflakes and Nb2C nanosheets in the prepared BP/Nb2C composite. The polarization of Nb centers by adjacent BP sites gives rise to the formation of positively centered Nb atoms and BP‐polarized Nb atoms, which synergistically catalyze the cleavage of N–O bonds in HNO2* to form NO*. In addition, the stabilization of monatomic *N by the BP/Nb2C composite is also enhanced compared with BP nanoflakes and Nb2C nanosheets. As a result, both the ammonia yield rate and Faraday efficiency of the BP/Nb2C composite are much higher than that of BP nanoflakes and Nb2C nanosheets. Overall, this work shows the great potential for constructing a strong interfacial polarization to improve the catalytic performance of MXenes‐based electrocatalysts.

Multifunctional black phosphorus pressure sensors with bending angle monitoring and direction recognition characteristics

“…The characteristic peaks of BP nanoflakes corresponding to the (002), (012), (004) and (111) crystal planes are identified in agreement with those reported previously. 41,42 The lattice spacing was calculated to be 0.53 nm according to the diffraction peak of the (002) plane. As observed from the AFM image and height profiles (Fig.…”

“…1e and the well-defined characteristic peaks centered at 360, 437 and 464 cm −1 correspond to the A g 1 (out-of-plane mode), B 2g (zigzag direction, in-plane modes) and A g 2 (armchair direction, in-plane modes) vibrational modes, respectively. 40,41,43,44 To further investigate the composition and chemical state, XPS analysis of pristine BP was performed. The predominant peaks of the P 2p 1/2 and P 2p 3/2 core level are respectively located at 130.5 eV and 129.7 eV, indicating an intense P–P bond in pristine BP, which is in good agreement with the data reported previously.…”

“…The predominant peaks of the P 2p 1/2 and P 2p 3/2 core level are respectively located at 130.5 eV and 129.7 eV, indicating an intense P–P bond in pristine BP, which is in good agreement with the data reported previously. 39,41,45 Besides, a very weak peak centered at 134.1 eV indexed to the P–O bond is observed, suggesting a very small amount (∼4.7%) of surface phosphorus oxidized on the BP surface because of exposure to the air. The above-mentioned results confirm that prepared BP possesses high crystallinity and high purity.…”

Emerging MXene-based electrocatalysts for efficient nitrate reduction to ammonia: recent advance, challenges, and prospects

“…For NO 3 -RR, the FE and NH 3 yield of MIL-101(Fe)@Nb 2 C reached 89.9% and 199.68 mg h -1 cm -2 , respectively. The heterogeneous structure of different 2D materials can regulate the overall electronic structure of the composite [64][65][66][67] .…”

A Graphdiyne Nanoreactor for Conversion of NO3− to NH3 from Wastewater

“…As the electrocatalytic NO 3 − -to-NH 3 conversion is an eight-electron transfer reaction and involves multiple plausible reaction pathways (NO 2 , NO, NOH, N 2 , NH 2 OH, NH 2 NH 2 , and NH 3 ). [5,[17][18][19][20] The limited 3D space formed by the nanoreactors is considered to play a domain-limiting effect resulting in local enrichment of nitrate, which facilitates the catalytic process. The coupling selectivity of N─H to NH 3 therefore could be promoted.…”