A Review of Electrocatalytic Reduction of Dinitrogen to Ammonia under Ambient Conditions

Abstract

The production of ammonia (NH3) from molecular dinitrogen (N2) under mild conditions is one of the most attractive topics in the field of chemistry. Electrochemical reduction of N2 is promising for achieving clean and sustainable NH3 production with lower energy consumption using renewable energy sources. To date, emerging electrocatalysts for the electrochemical reduction of N2 to NH3 at room temperature and atmospheric pressure remain largely underexplored. The major challenge is to achieve both high catalytic activity and high selectivity. Here, the recent progress on the electrochemical nitrogen reduction reaction (NRR) at ambient temperature and pressure from both theoretical and experimental aspects is summarized, aiming at extracting instructive perceptions for future NRR research activities. The prevailing theories and mechanisms for NRR as well as computational screening of promising materials are presented. State‐of‐the‐art heterogeneous electrocatalysts as well as rational design of the whole electrochemical systems for NRR are involved. Importantly, promising strategies to enhance the activity, selectivity, efficiency, and stability of electrocatalysts toward NRR are proposed. Moreover, ammonia determination methods are compared and problems relating to possible ammonia contamination of the system are mentioned so as to shed fresh light on possible standard protocols for NRR measurements.

Atomic Modulation, Structural Design, and Systematic Optimization for Efficient Electrochemical Nitrogen Reduction

“…In spite of the difficulty of the first stage of NRR, the subsequent PET processes are thermodynamically facile. There are so‐called scaling relations that describe the relationships between relative adsorption energies of N x H y intermediates based on ideal models . These scaling relationships are detrimental to developing an optimal model electrocatalyst that executes all nitrogen electroreduction steps in thermodynamically neutral/downhill modes toward ammonia generation.…”

“…Instead, the associative pathway, in which cleavage of NN bond is accompanied by the release of the first ammonia molecule, prevails in electrochemical NRR. The associative pathway consists of distal, alternating (mono‐adsorbed mode), and enzymatic (dual‐adsorbed mode) pathways . In the distal pathway, the two end‐on adsorbed nitrogen atoms are successively hydrogenated to generate ammonia molecules.…”

“…Depending on the manner of energy input and reaction route, the emerging nitrogen fixation methods can be categorized into biochemical, photocatalytic, plasma‐chemical, chemical looping, and electrochemical approaches . Among these alternatives, the electrochemical method that utilizes electricity from renewable solar or wind energy as the energy input is highly desirable for energy conservation efforts in ammonia production . This process is driven by the thermodynamic force of flexibly controlled electrochemical potentials, enabling dinitrogen fixation to ammonia upon addition of protons and electrons under ambient conditions.…”

Modulierung der elektronischen Strukturen anorganischer Nanomaterialien für eine effiziente elektrokatalytische Wasserspaltung

“…[8] In Bezug auf eine niedrige Edelmetallbeladung haben sich das Design von Nanostrukturen, wie Kern-Schale-Heterostrukturen, und die Modulierung mit Elektrokatalytische Wasserspaltung ist eine der vielversprechendsten nachhaltigen Technologien zur Energieumwandlung,i st aber eingeschränkt durchd ie trägen elektrochemischen Reaktionen. [13][14][15][16] FürN ichtedelmetall-Materialien wurden verschiedene Strategien untersucht, um die katalytische Leistungsfähigkeit zu steigern;z ud iesen gehçren hauptsächlich Oberflächenmodifizierung,S pannungsbearbeitung,P hasenübergang und Heterostruktur-Design. Verschiedene Verfahren sind zur Aktivitätsoptimierung dieser Nanokatalysatoren entwickelt worden.…”

“…[21] Da die Leitfähigkeit und Adsorptionsstärke der Intermediate -Letztgenannte ist äquivalent zur Reaktionsbarriere -a ls Effekte der elektronischen Struktur unmittelbar die Reaktionkinetik bestimmen sollten, hat man die elektronische Struktur als wichtigen Deskriptor identifiziert, um das jeweilige katalytische Verhalten zu erklären. [10,15] In diesem Aufsatz fassen wir die Strategien zur Steuerung der elektronischen Strukturen anorganischer Nanomaterialien fürd ie Wasserspaltung zusammen und stellen den Zusammenhang zwischen Struktur,e lektronischem Verhalten und Aktivitäth eraus.D ie hierzu angewendeten Strategien lassen sich wie folgt klassifizieren:1 )künstlicher Defekt, 2) Spannungsmanipulation, 3) Phasenübergang und 4) Heterostruktur (Abbildung 1). [24] Die Gruppe von Xie hob fürultradünne zweidimensionale (2D-)Feststoffe die Modulation von Ladung und Spinordnung hervor und klärte die Struktur-Eigenschafts-Beziehungen auf.…”