Synergy electrocatalysis between palladium and cobalt aligned on carbon nanosheet architectures for...

The integration of the electrochemical nitrate reduction reaction (eNO₃RR) and sulfur oxidation reaction (SOR) represents an effective strategy for the removal of harmful nitrates and sulfides from wastewater. However, the development of a cost-effective and high-performance bifunctional electrocatalyst remains a significant challenge. In this study, a trace amount of Pd is introduced into Co, N-doped carbon nanosheet arrays anchored on carbon cloth (Pd-Co@NC/CC), serving as a bifunctional electrocatalyst for cathodic eNO₃RR and anodic SOR. This catalyst achieves a maximum ammonia (NH₃) yield of 500.1 ± 0.8 μmol h^-1 cm^-2 with a Faraday efficiency of 93.1 ± 1.4 % under alkaline conditions. Theoretical calculations indicate that the cooperative interaction between Pd and Co in Pd-Co@NC/CC facilitates NO₃^- adsorption through Co sites, while Pd sites accelerate NH₃ desorption, thereby enhancing eNO₃RR performance. Furthermore, the potential for SOR with Pd-Co@NC/CC is only 0.22 V at 10 mA cm^-2, which is substantially lower than that of the oxygen evolution reaction (OER). Additionally, the Pd-Co@NC/CC||Pd-Co@NC/CC configuration achieves a potential of only 0.20 V at 10 mA cm^-2 for cathodic eNO₃RR and anodic SOR, markedly lower than the coupling of eNO₃RR with OER (0.99 V). This study provides a viable strategy for the resource utilization of nitrate/sulfide-containing wastewater.