New Insights into Electrochemical Ammonia Oxidation on Pt(100) from First Principles

Abstract

The electrocatalytic ammonia oxidation reaction (AOR) to molecular dinitrogen (N2) is an essential component within a sustainable nitrogen cycle. The state-of-the-art Pt nanocatalyst, preferably terminated with (100) facets, suffers from a large overpotential (>0.5 V) and rapid deactivation, the origin of which remains largely unexplained due to the intrinsic complexity of solid-electrolyte interfaces. Within the framework of grand-canonical density functional theory (GC-DFT), we show that on Pt(100) the dehydrogenation of *NH2 is the potential determining step and that the *OH species, thermodynamically stable at >0.5 V vs RHE while overlooked in previous studies, plays an important role in kinetics by preferential stabilization of *NH via hydrogen bonding. Attributed to such favorable adsorbate–adsorbate interactions, *NH2 dehydrogenation is thermoneutral at 0.5 V vs RHE forming *NH species that can then dimerize easily at the 4-fold hollow sites, capturing the experimentally observed onset potential. At high operating potentials (>0.63 V vs RHE) where the *NH dehydrogenation to *N becomes thermodynamically feasible, surface deactivation occurs. However, the dimerization of *N with *N or *NH is kinetically facile, which suggests that the adsorbed *N is only the precursor to poisoning species, e.g., *NO, on Pt(100). The mechanistic insights obtained in this study could be exploited in new strategies of designing active, selective, and robust electrocatalysts for ammonia oxidation.

Transition‐Metal Borides (MBenes) as New High‐Efficiency Catalysts for Nitric Oxide Electroreduction to Ammonia by a High‐Throughput Approach

“…First, we assume the entire route reaction network, considering the detailed binding properties of intermediate species and the corresponding limiting potentials of elementary reaction steps, and then, the most favorable pathway and RDS will be confirmed. [ 24 ] The competitive HER was also considered and compared on the MBene catalysts, and it was found that most of these MBene candidates have high selectivity for the NORR except for Ti 2 B 2 , V 2 B 2 , and Zr 2 B 2 . We also evaluated the electronic properties, studied the electron transfer processes of this new class of 2D materials for NORR and compared them with 2D MXenes.…”

Advanced Electrocatalysis for Energy and Environmental Sustainability via Water and Nitrogen Reactions

“…The *OH species, thermodynamically stable at >0.5 V, plays a significant role in boosting kinetics via preferential stabilization of *NH through hydrogen bonding. [ 234 ] At the high operation potentials (>0.63 V vs RHE), when the *NH dehydrogenation to *N becomes thermodynamically favorable, surface deactivation occurs. However, the dimerization of *N with *N or *NH is kinetically facile, implying that the adsorbed *N is only the precursor to poisoning species (e.g., *NO) on Pt(100) surface.…”

Advances and challenges for experiment and theory for multi-electron multi-proton transfer at electrified solid–liquid interfaces

“…276 Also, calculations with dynamical solvent have been performed 277,278 using the blue moon ensemble 279 method. Pioneering studies have shown the importance of analyzing the kinetics at constant potential rather than constant particle number as well as demonstrated the viability of GCE-TST in computing electrocatalytic rate constants from first principles for a wide class of electrocatalytic PCET reactions such as for hydrogen evolution, 64,65,272,275 CO 2 reduction, 266,280 CO reduction, 281 NH 3 oxidation, 282 nitrogen reduction, 283 and oxygen reduction reactions, 277 for example. Yet, all these first principles studies thus far have focused on classical reactions and neglected e.g.…”