Single-step in situ synthesis of MoO2-faceted structures as highly efficient HER electrocatalysts and electrode materials for pseudocapacitors

Abstract

In the present study, intermediate molybdenum oxide (MoO2) structures are synthesized via an in situ reduction process in an autoclave in the presence of nitrogen (N) and carbon (C), respectively. The carbothermic reduction favored the formation of MoO2 structures with smaller crystallite sizes. The synthesized samples showed the formation of laminar, faceted, and stacked structures as determined by FESEM and TEM analyses. The presence of C and N in the synthesized samples, elucidated by XPS analysis, contributed to the efficiency and stability of the electrolytic hydrogen evolution reaction (HER) and pseudocapacitance performance. The synthesized samples exhibited very low Tafel slopes (46.3-47.8 mV dec-1) for the HER activity and showed very high stability (3000 CV cycles) over a wide voltage window (0-1 V). Moreover, the synthesized samples required a very low overpotential of 80 mV to produce a current density of 10 mA cm-2. The cyclic voltammetry (CV) and galvanic charge- discharge (GCD) characteristics revealed the actual pseudocapacitor behavior of the synthesized samples. CV and GCD signals revealed the potential application of the synthesized samples for pseudocapacitor applications. The active sites on the edges and N and C in the synthesized samples enhanced their potential use as electrocatalysts for the HER and electrode materials for pseudocapacitors.