Partial sulfurization enabled SO42- decorated NiFe2O4 for enhanced electrocatalytic urea oxidation

Abstract

Urea-assisted water splitting for hydrogen production is an emerging technology, but developing efficient urea oxidation reaction (UOR) electrocatalysts remains challenging. Hence, the nonmetallic anionic group SO₄^2- decorated NiFe₂O₄ (S_x-NiFe₂O₄) catalyst is cleverly designed via a facile one-pot co-precipitation process followed by a sulfurization strategy. The decoration with SO₄^2- not only increased the high-valent Ni content and active sites in the catalyst but also significantly improved its hydrophilicity and stability. With the optimal sulfurization amount, S_0.5-NiFe₂O₄ only 1.48 V is sufficient to achieve 100 mA cm⁻² and staggering mass activity of 5.6 A cm⁻² mg⁻¹ at 1.6 V. Strikingly, the overall urea electrolyzer with S_0.5-NiFe₂O₄ anode only requires 1.59 V to drive a current density of 50 mA cm⁻² and maintains stably for 100h at a current density of 10 mA cm⁻². Besides, this urea overall splitting system can be powered by a 1.5 V voltaic battery. This study provides a strategy for designing UOR catalysts with high catalytic performance from the aspect of taking advantage of nonmetallic anionic groups.