Mitigating Intraphase Catalytic-Domain Transfer via CO2 Laser for Enhanced Nitrate-to-Ammonia Electroconversion and Zn-Nitrate Battery Behavior

Abstract

Developing sustainable energy solutions is critical for addressing the dual challenges of energy demand and environmental impact. In this study, a zinc-nitrate (Zn−NO3−) battery system was designed for the simultaneous production of ammonia (NH3) via the electrocatalytic NO3− reduction reaction (NO3RR) and electricity generation. Continuous wave CO2 laser irradiation yielded precisely controlled CoFe2O4@nitrogen-doped carbon (CoFe2O4@NC) hollow nanocubes from CoFe Prussian blue analogs (CoFe-PBA) as the integral electrocatalyst for NO3RR in 1.0 M KOH, achieving a remarkable NH4+ production rate of 10.9 mg h−1 cm−2 at −0.47 V versus Reversible Hydrogen Electrode with exceptional stability. In situ and ex situ methods revealed that the CoFe2O4@NC surface transformed into high-valent Fe/CoOOH active species, optimizing the adsorption energy of NO3RR (*NO2 and *NO species) intermediates. Furthermore, density functional theory calculations validated the possible NO3RR pathway on CoFe2O4@NC starting with NO3− conversion to *NO2 intermediates, followed by reduction to *NO. Subsequent protonation forms the *NH and *NH2 species, leading to NH3 formation via final protonation. The Zn−NO3− battery utilizing the CoFe2O4@NC cathode exhibits dual functionality by generating electricity with a stable open-circuit voltage of 1.38 V versus Zn/Zn2+ and producing NH3. This study highlights the innovative use of CO2 laser irradiation to transform Prussian blue analogs into cost-effective catalysts with hierarchical structures for NO3RR-to-NH3 conversion, positioning the Zn−NO3− battery as a promising technology for industrial applications.