Phase control and stabilization of 1T-MoS2 via black TiO2-x nanotube arrays supporting for electrocatalytic hydrogen evolution

1T phase MoS(1T-MoS) is a promising substitute of platinum electrocatalyst for hydrogen evolution reaction(HER) due to its high intrinsic activity but suffering from thermodynamical instability.Although great efforts have been made to synthesize 1T-MoSand enhance its stability, it remains a big challenge to realize the phase control and stabilization of 1T-MoS. Herein, based on crystal field theory analysis, we propose a new solution by designing an electrocatalyst of 1T-MoSnanosheets anchoring on black TiOnanotube arrays in-situ grown on Ti plate(1T-MoS/TiO@Ti). The black TiOsubstrate is expected to play as electron donors to increase the charge in Mo 4 d orbits of 1T-MoSand thus weaken the asymmetric occupation of electrons in the Mo 4 d orbits. Experimental results demonstrate that black TiOnanotubes shift electrons to MoSand induce MoSto generate more 1 T phase due to stabilizing the 1T-MoSnanosheets compared with a Ti substrate. Thus 1T-MoS/TiO@Ti shows much improved HER performance with a small Tafel slope of 42 m V decand excellent catalytic stability with negligible degradation for 24 h. Theoretical calculations confirm that the black TiOsubstrate can effectively stabilize metastable 1T-MoSdue to electrons transferring from black TiOto Mo 4 d orbits.This work sheds light on the instability of 1T-MoSand provides an essential method to stabilize and efficiently utilize 1T-MoSfor HER.