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.

Salts-assistant synthesis of g-C3N4/Prussian-blue analogue/nickel foam with hierarchical structures as binder-free electrodes for supercapacitors

The exploitation of high-performance electrode materials is significant to develop supercapacitors with satisfied energy and power output properties. In this study, a g-C₃N₄/Prussian-blue analogue (PBA)/Nickel foam (NF) with hierarchical micro/nano structures was developed by a simple salts-directed self-assembly approach. In this synthetic strategy, NF acted as both 3D macroporous conductive substrate and Ni source for PBA formation. Moreover, the incidental salt in molten salt-synthesized g-C₃N₄ nanosheets could regulate the combination mode between g-C₃N₄ and PBA to generate interactive networks of g-C₃N₄ nanosheets-covered PBA nano-protuberances on NF surfaces, which further expended the electrode/electrolyte interfaces. Based on the merits from this unique hierarchical structure and the synergy effect of PBA and g-C₃N₄, the optimized g-C₃N₄/PBA/NF electrode exhibited a maximum areal capacitance of 3366 mF cm^-2 at current of 2 mA cm^-2, as well as 2118 mF cm^-2 even under large current of 20 mA cm^-2. The solid-state asymmetric supercapacitor using g-C₃N₄/PBA/NF electrode possessed an extended working potential window of 1.8 V, prominent energy density of 0.195 mWh cm^-2 and power density of 27.06 mW cm^-2. Compared to the device with pure NiFe-PBA electrode, a better cyclic stability with capacitance retention rate of 80% after 5000 cycles was also achieved due to the protective effect of g-C₃N₄ shells on the etching of PBA nano-protuberances in electrolyte. This work not only builds a promising electrode material for supercapacitors, but also provide an effective way to apply molten salt-synthesized g-C₃N₄ nanosheet without purification.

Polyaniline@MOF fiber derived Fe–Co oxide-based high performance electrocatalyst

Electrochemical energy conversion and storage are important and coupled with a number of electrocatalytic processes.