Pulse electrodeposited, morphology controlled organic–inorganic nanohybrids as bifunctional electrocatalysts for urea oxidation

Abstract

Organic–inorganic nanohybrids with nanoscale architectures and electrocatalytic properties are emerging as a new branch of advanced functional materials. Herein, nanohybrid organic–inorganic nanosheets are grown on carbon paper via a pulse-electrochemical deposition technique. A benzo[2,1,3]selenadiazole-5-carbonyl protected dipeptide BSeFL (BSe = benzoselenadiazole; F = phenylalanine; and L = leucine) cross-linked with Ni²⁺ ions (Ni-BSeFL) and nickel hydroxide (Ni(OH)₂) in a BSeFL/Ni(OH)₂ electrode exhibits stable electrocatalytic activity toward urea oxidation. The cross-linked nanosheet morphology of nanohybrids was optimized by controlling the reduction potential during pulse electrodeposition. The BSeFL/Ni(OH)₂ (−1.0 V) nanohybrid deposited at −1.0 V provides abundant active sites of Ni³⁺ with low charge transfer resistance (R_CT) and high exchange current density (J₀) at the electrocatalytic interface. The nanohybrids with Ni-BSeFL and Ni(OH)₂ show low overpotential and superior stability for electrocatalytic urea electro-oxidation. The BSeFL/Ni(OH)₂ (−1.0 V) nanohybrid based electrode requires a low potential of 1.30 V (vs. RHE) to acquire a current density of 10 mA cm⁻² for the urea oxidation reaction (UOR) in urea containing alkaline solution which is lower than that for water oxidation in alkaline solution (1.49 V vs. RHE). The organic–inorganic nanohybrid BSeFL/Ni(OH)₂ (−1.0 V) shows durability over 10 h for oxygen evolution and urea electro-oxidation, thereby confirming the BSeFL/Ni(OH)₂ (−1.0 V) nanohybrid-based electrode as an efficient electrocatalyst.