Synergistic enhancement of Zn-air battery performance via integration of Ni-doped cobalt sulfide nanoparticles within N, S-doped carbon matrix.

Exploring precious metal-free bifunctional electrocatalysts for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is essential for the practical application of rechargeable Zn-air battery (ZAB). Herein, Ni-doped Co9S8 nanoparticles embedded in a defect-rich N, S co-doped carbon matrix (d-NixCo9-xS8@NSC) are synthesized via a facile pyrolysis and acid treatment process. The introduction of abundant defects in both the carbon matrix and metal sulfide provides numerous active sites and significantly enhances the electrocatalytic performances for both the ORR and OER. d-NixCo9-xS8@NSC exhibits a superior half-wave potential of 0.841 V vs. RHE for the ORR and delivers a low overpotential of 0.329 V at 10 mA cm-2 for the OER. Additionally, Zn-air secondary battery using d-NixCo9-xS8@NSC as the air cathode displays a higher specific capacity of 734 mAh gZn-1 and a peak power density of 148.03 mW cm-2 compared to those of state-of-the-art Pt/C-RuO2 (673 mAh gZn-1 and 136.9 mW cm-2, respectively). These findings underscore the potential of d-NixCo9-xS8@NSC as a high-performance electrocatalyst for secondary ZABs, offering new perspectives on the design of efficient noble metal-free electrocatalysts for future energy storage and conversion applications.

Regulating the electronic structure of Ni2P by one-step Co, N dual-doping for boosting electrocatalytic performance toward oxygen evolution reaction and urea oxidation reaction.

The development of efficient bifunctional electrocatalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is critical for hydrogen production and wastewater purification. In this work, we propose a facile synthetic method for Co and N dual-doped Ni2P directly grown on Ni foam (Co-Ni2P-N/NF) using hydrothermal and annealing process. Simultaneous Co and N dual-doping into Ni2P not only modifies the surface electronic structure, but also generates a multitude of active sites with high valence states, which are beneficial for improving electrocatalytic kinetics for both OER and UOR. As a result, the Co-Ni2P-N/NF catalyst exhibits a low overpotential of 329 mV to deliver a current density of 100 mA cm-2 for OER in alkaline solution, which is much lower than that of the state-of-the-art RuO2 electrocatalyst. In addition, the urea-assisted water oxidation process exhibits a significant reduction of approximately 163 mV in the required potential at 100 mA cm-2 compared to that of the OER, which highlights the remarkable potential of the prepared Co-Ni2P-N/NF electrocatalyst in facilitating the purification of wastewater and hydrogen production with significantly lower energy consumption.