Efficient Electrocatalytic Nitrate-to-Ammonia Enabled by Reversible Lattice-Oxygen Control

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Optimizing catalytic performance is crucial for sustainable chemical transformations.
• Nitrate reduction (NO3-RR) faces challenges balancing high Faradaic efficiency (FE) and low overpotential.
• Transition metal oxides (TMOs) are promising electrocatalysts but require precise surface tuning.

Purpose of the Study:

• To develop a novel strategy for enhancing NO3-RR performance by regulating surface oxygen activity.
• To investigate the relationship between metal-oxygen covalency and catalytic activity in perovskite oxides.
• To elucidate the reaction mechanism for improved nitrate reduction.

Main Methods:

• Synthesis and characterization of A-site-substituted La1-xSrxCoO3 perovskites.
• Electrochemical performance testing for NO3-RR.
• Computational modeling to understand surface oxygen activity and metal-oxygen covalency.
• In-situ mechanistic studies to probe active sites and reaction pathways.

Main Results:

• Surface oxygen activity, tuned by metal-oxygen covalency, shows distinct "volcano" and "W-shaped" dependencies on NH3 yield rate and FE.
• La0.5Sr0.5CoO3 exhibited exceptional activity and selectivity for NO3-RR due to balanced metal-oxygen covalency.
• A switchable active site mechanism involving lattice-oxygen dynamics was uncovered, circumventing potential-limiting steps.

Conclusions:

• Quantitative regulation of surface oxygen activity via metal-oxygen covalency is an effective strategy for enhancing NO3-RR.
• The discovered mechanism provides insights into designing advanced TMOs for oxygen-sensitive reactions.
• This work deepens the understanding of surface dynamics in electrocatalysis.