Design of Porous Core–Shell Manganese Oxides to Boost Electrocatalytic Dinitrogen Reduction

Abstract

Harnessing the electrochemical nitrogen reduction reaction (NRR), where renewable electricity and H 2 O are used for NH 3 production, is regarded as an effective and clean protocol for N 2 fixation. The design and development of new active, selective, and durable NRR electrocatalysts are expected to achieve this. Here, we design a well-defined porous core−shell heterostructure comprising Mn 2 O 3 −MnO (as the core) and Mn 3 O 4 (as the shell). The unique composite is shown to efficiently facilitate N 2 adsorption and reduction in a neutral electrolyte, delivering an impressive NH 3 FE (∼23.8%) with a reasonable NH 3 formation rate (22.4 μg NH3 h −1 mg cat −1) at a cathodic voltage of −0.3 V (versus reversible hydrogen electrode). The electrocatalytic properties can be readily modulated by tuning the shell thickness. Our measured performance surpasses those of most nonmetallic, transition-metal-, and noble-metal-based catalysts reported in the prior literature. Equally importantly, the electrocatalytic activity maintains good stability up to 60 h. The outstanding electrochemical performance is attributed to the combined advantages of a large interface between the metal oxides and a unique core−shell structure with a high density of surface-exposed sites, pores, and oxygen vacancies.

Self-supported V-doped NiO electrocatalyst achieving a high ammonia yield of 30.55 μg h−1 cm−2 under ambient conditions

“…34 As shown in Fig. 5c, after electrolysis over V/NiO using 15 excellent accuracy of the formation rates and the NRR performance reliability of V/NiO. Apart from the NRR activity, durability is another critical quality for electrocatalysts.…”

“…5b). 33 To trace the origin of the N source, we performed isotopic labeling experiment using 15 N 2 to replace 14 N 2 as the supply gas. 34 As shown in Fig.…”

“…2,10 However, these catalysts are restricted by the scarcity and high cost of noble metals, which makes them unsuitable for large-scale application. To find good alternatives, massive works have been reported on the development of non-noble transition metal-based catalysts towards the ENRR, including transition metal nitrides, 11,12 oxides, [13][14][15] sulfides, 16,17 chalcogenides 18 and carbides. 19 Among them, transition metal oxides (TMOs) have advantages such as an easy synthetic route, redox stability and tunable electron states, which make TMOs a promising class of electrocatalysts.…”

Recent progress of photocatalysts based on tungsten and related metals for nitrogen reduction to ammonia

“…Non-noble metal oxides have gained tremendous expectations as promising alternative NRR catalysts primarily owing to their high chemical stability, ease of synthesis, and minimization of noble metals consumption (Liang Gao et al, 2022;Zhen Zhao et al, 2022). Only a few metal oxides such as VO 2 (Haiguang Zhang et al, 2019), Ta 2 O 5 (Fu et al, 2019), Nb 2 O 5 (Han et al, 2018;Kong et al, 2019), NbO 2 , and ZrO 2 have been reported for electrocatalytic NRR, However, these metal oxides suffer from large band gap, poor light absorption capacity toward visible light, low quantum efficiency, and fast recombination rate of photogenerated excitons, restricting their applications in photocatalytic NRR.…”

Mn-Doped Bi2O3 Nanosheets from a Deep Eutectic Solvent toward Enhanced Electrocatalytic N2 Reduction

“…39 Additionally, the advantageous coexistence of occupied and unoccupied 3d orbitals in Mn element is conducive to adsorbing and activating N 2 molecules. 40,41 Specifically, Mnbased materials possess inferior HER activity by virtue of the hardness in forming the Mn−H bond, 42,43 Bi 2 O 3 electrocatalyst holds great promise for the NRR. However, such a concept has not been explored so far.…”