Composite Metal–Organic Framework-Derived NiCoP/MoS2 Heterostructure with Superior Electrocatalytic Credentials for Urea and Methanol Oxidation

Abstract

The urea oxidation reaction (UOR) and methanol oxidation reaction (MOR) are the most practical alternative counter-reactions to the hydrogen evolution reaction in the overall electrochemical water splitting process. The thermodynamic gains in terms of lower water-splitting potentials compared to the oxygen evolution reaction (OER) can be cashed in if the kinetics of the UOR and MOR can suitably be controlled. This has called for the development of suitable cost-effective and non-precious catalysts for the processes. Herein, we report the synthesis of a heterostructured composite catalyst that incorporates the versatile NiCoP and MoS2 components through a composite MOF degradation route for efficient UOR and MOR catalysis in an alkaline medium (0.5 M NaOH). The intimate union of the components generates the strong synergistic influence of catalytically active phosphide and sulfide components toward excellent electrocatalytic UOR and MOR performance. The cyclic voltammetry and linear sweep voltammetry analyses reveal anodic UOR and MOR peak currents of 92.5 and 214.2 mA cm–2, respectively. Also, a benchmark current of 50 mA cm–2 is achieved at voltages of 1.55 and 1.53 V versus the reversible hydrogen electrode for the UOR and MOR, respectively, which reflects a considerable kinetic facility over the OER. The electrochemical impedance (EIS) measurements reveal considerably enhanced kinetics over the control samples and the OER on the catalyst systems. Additionally, the catalytic synergism is clearly reflected as the catalytic credentials of the composite catalysts surpass those of the individual control samples significantly. The catalytic features compare well with the best catalysts reported for the UOR and MOR in the alkaline medium.