Morphology and distribution of in-situ grown MoP nanoparticles on carbon nanotubes to enhance hydrogen evolution reaction

Highlights: • MoP nanoparticles in-situ grown on MWCNTs for enhanced hydrogen evolution reaction with a facile path. • Strong interconnections of MoP nanoparticles with the MWCNTs obtained by in-situ transformation of MoSx to MoP. • The morphology and distribution of MoP was tuned by Mo-C ratio for high active sites. • The MoP/MWCNTs with Mo-C ratio of 1/2 significantly enhance the HER performance. • MoP/MWCNTs -1/2 also exhibited excellent stability performance. -- Abstract: Molybdenum phosphides (MoP) have been demonstrated to be effective electrocatalysts for hydrogen evolution reaction (HER). The active sites of MoP particles and interface connections of MoP particles with carbon nanotube conducting networks are crucial to enhance their electrocatalytic performance. However, it is a big challenge to control the active sites of MoP and the interconnections between active materials with conducting networks. An in-situ method to fabricate MoP nanoparticles on multi-walled carbon nanotubes (MWCNTs) has been investigated to give MoP/MWCNTs with high active sites of MoP nanoparticles and strong interconnections between MoP nanoparticles and conducting MWCNTs from in-situ grown molybdenum sulfide (MoS_x) on MWCNTs (MoS_x/MWCNTs) precursors. The MoS_x on MWCNTs were directly converted into MoP nanoparticles with strong interconnections with the carbon nanotube conducting networks. The morphology and distribution of MoP were adjusted by changing the Mo-C ratio to obtain large amount of active sites. The MoP/MWCNTs with Mo-C ratio of 1/2 have been demonstrated to significantly enhance the HER performance. Overpotentials of 109 mV and 155 mV have been obtained at 10 mA cm^-2 with corresponding small Tafel slope of 56.5 mV dec^-1 and 56.8 mV dec^-1 in acidic and alkaline solution, respectively.