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

Abstract

1T phase MoS2 (1T-MoS2) 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-MoS2 and enhance its stability, it remains a big challenge to realize the phase control and stabilization of 1T-MoS2. Herein, based on crystal field theory analysis, we propose a new solution by designing an electrocatalyst of 1T-MoS2 nanosheets anchoring on black TiO2−x nanotube arrays in-situ grown on Ti plate (1T-MoS2/TiO2−x@Ti). The black TiO2−x substrate is expected to play as electron donors to increase the charge in Mo 4d orbits of 1T-MoS2 and thus weaken the asymmetric occupation of electrons in the Mo 4d orbits. Experimental results demonstrate that black TiO2−x nanotubes shift electrons to MoS2 and induce MoS2 to generate more 1T phase due to stabilizing the 1T-MoS2 nanosheets compared with a Ti substrate. Thus 1T-MoS2/TiO2−x@Ti shows much improved HER performance with a small Tafel slope of 42 mV dec−1 and excellent catalytic stability with negligible degradation for 24 h. Theoretical calculations confirm that the black TiO2−x substrate can effectively stabilize metastable 1T-MoS2 due to electrons transferring from black TiO2−x to Mo 4d orbits. This work sheds light on the instability of 1T-MoS2 and provides an essential method to stabilize and efficiently utilize 1T-MoS2 for HER.