To achieve efficient ammonia synthesis via electrochemical nitrogen reduction reaction (NRR), a qualified catalyst should have both high specific activity and large active surface area. However, integrating these two merits into one single material remains a big challenge due to the difficulty in balancing multiple reaction intermediates. Here, it is demonstrated that the boron‐analogues of MXenes, namely “MBenes”, could cope with the challenge and achieve the high activity and large reaction region simultaneously toward NRR. Using extensive density functional theory computations and taking 16 MBenes as representatives, it is identified that seven MBenes (CrB, MoB, WB, Mo2B, V3B4, CrMnB2, and CrFeB2) not only have intrinsic basal plane activity for NRR with limiting potentials ranging from −0.22 to −0.82 V, but also possess superior capability of suppressing the competitive hydrogen evolution reaction. Particularly, different from the MXenes whose surface oxidation may block the active sites, once oxidized, these MBenes can catalyze NRR via the self‐activating process, reducing O*/OH* into H2O* under reaction conditions, and favoring the N2electroreduction. As a result, the exceptional activity and selectivity, high active area (≈1019m−2), and antioxidation nature render these MBenes as pH‐universal catalysts for NH3production without introducing any dopants and defects.
Ammonia (NH3) electrosynthesis gains significant attention as NH3is essentially important for fertilizer production and fuel utilization. However, electrochemical nitrogen reduction reaction (NRR) remains a great challenge because of low activity and poor selectivity. Herein, a new class of atomically dispersed Ni site electrocatalyst is reported, which exhibits the optimal NH3yield of 115 µg cm−2h−1at –0.8 V versus reversible hydrogen electrode (RHE) under neutral conditions. High faradic efficiency of 21 ± 1.9% is achieved at ‐0.2 V versus RHE under alkaline conditions, although the ammonia yield is lower. The Ni sites are stabilized with nitrogen, which is verified by advanced X‐ray absorption spectroscopy and electron microscopy. Density functional theory calculations provide insightful understanding on the possible structure of active sites, relevant reaction pathways, and confirm that the Ni‐N3sites are responsible for the experimentally observed activity and selectivity. Extensive controls strongly suggest that the atomically dispersed NiN3site‐rich catalyst provides more intrinsically active sites than those in N‐doped carbon, instead of possible environmental contamination. This work further indicates that single‐metal site catalysts with optimal nitrogen coordination is very promising for NRR and indeed improves the scaling relationship of transition metals.
more » « less- Award ID(s):
- 1804534
- NSF-PAR ID:
- 10457965
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Small Methods
- Volume:
- 4
- Issue:
- 6
- ISSN:
- 2366-9608
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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