Fe-Single-Atom Catalysts on Nitrogen-Doped Carbon Nanosheets for Electrochemical Conversion of Nitrogen to Ammonia

Abstract

Electrochemical nitrogen reduction reaction (NRR) has been established as a promising and sustainable alternative to the Haber−Bosch process, which requires intensive energy to produce ammonia. Unfortunately, NRR is constrained by the high adsorption/activation of the N 2 energy barrier and the competing hydrogen evolution reaction, resulting in low faradic efficiency. Herein, a well-dispersed iron single-atom catalyst was successfully immobilized on nitrogen-doped carbon nanosheets (Fe SAC -N-C) synthesized from pre-hydrothermally derived Fe-doped carbon quantum dots with an average particle size of 2.36 nm and used for efficient electrochemical N 2 fixation at ambient conditions. The as-synthesized Fe SAC -N-C catalyst records an onset potential of 0.12 V RHE , exhibiting a considerable faradic efficiency of 23.7% and an NH 3 yield rate of 3.47 μg h −1 cm −2 in aqueous 0.1 M KOH electrolyte at a potential of −0.1 V RHE under continuous N 2 feeding conditions. The control experiments assert that the produced NH 3 molecules only emerge from the dissolved N 2 -gas, reflecting the remarkable stability of the nitrogen−carbon framework during electrolysis. The DFT calculations showed the Fe SAC -N-C catalyst to demonstrate a lower energy barrier during the rate-limiting step of the NRR process, consistent with the observed high activity of the catalyst. This study highlights the exceptional potential of single-atom catalysts for electrochemical NRR and offers a comprehensive understanding of the catalytic mechanisms involved. Ultimately, this work provides a facile synthesis strategy of Fe SAC -N-C nanosheets with high atomic-dispersion, creating a novel design avenue of Fe SAC -N-C that can vividly have a potential applicability in the large spectrum of electrocatalytic applications.

First-Principles Insight into the Mechanistic Study of Electrochemical Cyanide Reduction Reaction on Post-Transition Metal Based Single-Atom Catalysts Anchored by Phthalocyanine Nanosheets

“…These include the capacity for catalytic creation employing an optimal minimum of valuable metals, the anticipated superior specificity of single atom catalysts (SACs) compared to clusters of nanosized particles exhibiting diverse dimensions, as well as the potential for SACs to serve as a connective link amidst homogeneous and heterogeneous catalysis. − However, as underscored by some contemporary studies, , there is a notable variance in the efficacy of SACs relative to that associated with vast metal interfaces, necessitating the reconsideration of relevant applicability of current broad-scope frameworks, such as those that consider local charges or spin polarization. During the recent years, a multitude of distinguished investigations has provided a comprehensive view of techniques studying both transition-metal based SACs − and transition-metal free SACs, − respectively, anchored on a series of suitable supports, demonstrating their significant potential in advancing electrocatalytic applications.…”

Modulation of Reactive Hydrogen Adsorbed on Dual-Active Site NiMoO4 Nanocubes for Reduction of Nitrate to Ammonia

“…Undoubtedly, a proper catalyst design is essential for the high efficiency and selectivity of the electrocatalytic NO 3 − RR to NH 3 . Nonprecious monometallic catalysts, such as iron, 13,14 cobalt, 15,16 and copper, 17−20 are the main choices for NO 3 − RR owing to their high cost-effectiveness, but their catalytic activity and selectivity are inadequate to meet the growing demand of NH 3 synthesis. Furthermore, other materials, nickel, have rarely been investigated because they are generally considered unsuitable for NO 3 − RR as the HER is their main competing reaction.…”

“…Undoubtedly, a proper catalyst design is essential for the high efficiency and selectivity of the electrocatalytic NO 3 – RR to NH 3 . Nonprecious monometallic catalysts, such as iron, , cobalt, , and copper, − are the main choices for NO 3 – RR owing to their high cost-effectiveness, but their catalytic activity and selectivity are inadequate to meet the growing demand of NH 3 synthesis. Furthermore, other materials, nickel, have rarely been investigated because they are generally considered unsuitable for NO 3 – RR as the HER is their main competing reaction. − However, the nitrate reduction process heavily relies on *H, which is produced via H 2 O splitting. − To address this issue, a strategy has been proposed to use new material design ideas to ensure that sufficient *H is obtained to achieve a high NH 3 conversion rate and inhibit the HER. , The main challenge facing this strategy is how to prevent the formation of hydrogen from *H.…”

Compositionally variant bimetallic Cu–Mn oxysulfide electrodes with meritorious supercapacitive performance and high energy density

“…Also, density functional theory (DFT) calculations were executed to scrutinize the electronic properties of oxysulfide structures, as DFT was proven to be a robust tool in examining the electronic properties. 27–32 To unveil the real functionality of the C 3 M 1 OS electrode, an asymmetric device was assembled employing commercial activated carbon (AC) as the negative pole and C 3 M 1 OS as the positive pole, with a weight of ∼4 mg, i.e. , commercial mass loading.…”

“…Also, density functional theory (DFT) calculations were executed to scrutinize the electronic properties of oxysulfide structures, as DFT was proven to be a robust tool in examining the electronic properties. [27][28][29][30][31][32] To unveil the real functionality of the C 3 M 1 OS electrode, an asymmetric device was assembled employing commercial activated carbon (AC) as the negative pole and C 3 M 1 OS as the positive pole, with a weight of B4 mg, i.e., commercial mass loading. The assembled device provided a very high energy density of 76.56 W h kg À1 along with a power density of 985.01 W kg À1 at 1 A g À1 with superior electrochemical stability and efficiency over 10 000 charge/discharge cycles.…”