Laser in situ synthesis of NiFe2O4 nanoparticle-anchored NiFe(OH)x nanosheets as advanced electrocatalysts for the oxygen evolution and urea oxidation reactions

The in situ growth of oxygen-vacancy-rich hybrid electrocatalysts with a high surface area is considered to be an effective strategy for enhancing the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) performance. However, in situ synthesis is often difficult due to multistep procedures and harsh conditions. Herein, NiFe2O4 nanoparticles are successfully grown in situ on NiFe(OH)(x) nanosheets via using unique laser ablation in liquids technology. The quenching effect of the pulsed laser and the reduction of BH4- promote the generation of oxygen-vacancy-abundant NiFe(OH)(x)/NiFe2O4 nanocomposites, and the weak alkalinity of the NaBH4 solutions accelerates the production of NiFe(OH)(x) nanosheets. Profited from the affluent oxygen vacancies and enhancive surface areas, the NiFe(OH)(x)/NiFe2O4 nanocomposites reveal enhancement in electrocatalytic OER performance with small overpotential of 249 mV at 10 mA cm(-2) and a Tafel slope of 40.1 mV dec(-1), accompanied by superior stability (the current density retention after 150 h is 98.5% of the initial value). In addition, the NiFe(OH)(x)/ NiFe2O4 hybrid electrocatalysts also exhibit excellent electrocatalytic performance for the urea oxidation reaction (a potential of 1.343 V at 10 mA cm(-2) and a Tafel slope of 19.9 mV dec(-1)). This work can provide guidance for exploring other hydroxide/oxide materials with abundant oxygen vacancies and high surface areas.