Balancing Atomic Hydrogen Supply and Nitrate Electroreduction for Enhanced Ammonia Synthesis on Pt-Cu 2 O/Cu Electrocatalysts

Abstract

Electrochemical nitrate reduction to ammonia represents a dual-purpose solution for environmental remediation and sustainable ammonia synthesis, yet faces intrinsic kinetic limitations from inefficient hydrogen adsorption, dominant hydrogen evolution pathways, and undesirable byproduct formation. Addressing these challenges, we engineered Pt-Cu 2 O/Cu-R and Pd-Cu 2 O/Cu-R electrocatalysts via cation exchange. Comprehensive structural characterization confirmed successful synthesis, with Pt-Cu 2 O/Cu-R exhibiting enhanced crystallinity and superior hydrogen adsorption capacity. In 0.1 M NaOH/0.1 M NO 3 -electrolyte, Pt-Cu 2 O/Cu-R achieved exceptional performance metrics with 86.55% Faradaic efficiency and 4.16 mg h -1 cm -2 ammonia yield at 75 mA cm -2 , significantly surpassing Pd-Cu 2 O/Cu-R and unmodified Cu 2 O/Cu-R. In situ spectroscopic studies revealed the operative mechanism that persistent Cu + species activate nitrogenous intermediates while adjacent platinum sites dissociate water, generating reactive hydrogen for sequential hydrogenation. This activity enhancement originates in platinum's unique ability to optimize the kinetic equilibrium between hydrogen generation and nitrate reduction demands. Furthermore, the catalyst maintained outstanding operational stability through 20 consecutive electrolysis cycles, demonstrating negligible performance decay. Our work establishes Pt-Cu 2 O/Cu-R as an efficient and robust platform for sustainable electrochemical ammonia synthesis.