Engineering of Bimetallic Cu–Pt Nanostructures for the Electrochemical Ammonia Synthesis via Nitrate Reduction

Abstract

The electrochemical nitrate reduction reaction (NO3RR) is an environmentally friendly and low carbon emission method that is attractive for producing high-value added NH3. However, NO3RR experiences poor selectivity and slow kinetics because of its complex reaction intermediates and the complicated process of eight electron transfer. Herein, the Cu-rich bimetallic nanocomposite CuPt on nanofibrillar networks of peptide bolaamphiphile hydrogels is reported as a high-performance NO3RR electrocatalyst for the conversion of NO3 – to NH3 at ambient temperature. The CuPt(3:1)@hydrogel in comparison with the CuPt(1:1)@hydrogel and CuPt(1:3)@hydrogel displays exceptional catalytic performance with a maximum Faradaic efficiency of 72.33% at −0.1 V (vs RHE) and a relatively high NH3 yield of 0.71 mg h–1 mgcat –1 at −0.3 V (vs RHE) in alkaline electrolyte (1 M KOH) containing 100 mM KNO3. The nanofibrillar networks of peptide bolaamphiphiles provide high catalytic active sites and increase proton transfer kinetics, which results in the enhancement of NO3RR performance. The control experiments support that the produced NH3 originated from NO3 – reduction rather than any impurities. The durability tests suggest that the CuPt(3:1)@hydrogel maintains excellent morphological and structural stability after long-term electroreduction. The as-synthesized CuPt nanostructures were characterized by FE-SEM, EDS, HR-TEM, XRD, rheology, and XPS analyses. The current strategy has the potential to create new opportunities for developing nanomaterials that are designed rationally for future electrocatalysts.