RESUMO
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 NH3 production rate of 10.9 mgh-1cm-2 at -0.47 V versus RHE 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, DFT 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 inspires the simple design of low-cost catalysts for NO3RR-to-NH3 conversion and positions the Zn-NO3- battery as a promising technology for industrial applications.
