Synthesis of MoO 2 on steel substrate for hydrogen evolution reaction in water splitting: a new approach

Metallic molybdenum dioxide (MoO 2 ) films were grown on stainless steel (SS) substrate by a simple hydrothermal process employing citric acid at different deposition times that acts as a chelating agent. The tuning of the bandgap of SS and MoO 2 favours the water splitting which could not be obtained on other conventional substrates. Initially, the morphology of MoO 2 was aggregated ultrathin nanosheets for a six-hour reaction time, and it changed to other diverse morphology by varying the reaction time. XRD data confirm the formation of MoO 2 nanoparticles. The electrochemical water activation studies show that 10-h (M10) MoO 2 film on SS is showing an excellent hydrogen evolution reaction (HER) catalyst with good stability (9 h). MoO 2 on SS displays a low onset overpotential of − 33 mV vs RHE with a Tafel slope of 39 mV/dec and − 138 mV vs RHE overpotential at 10 mA/cm 2 current density. The large active surface area and lesser electrochemical charge-transfer resistance offered by the MoO 2 nanostructures play a major role in the enhanced HER activity. Graphical Abstract