Vertical growth of compact and large-area MoS2 nanosheet arrays on Ti3C2Tx for efficient bifunctional electrochemical energy storage and hydrogen evolution

Abstract

The developments in hydrogen evolution reaction (HER) and supercapacitor technologies for electrochemical energy storage and conversion have received considerable attention. Although MoS2 is electrochemically active for both HER and supercapacitors, limited active sites, slow ionic transport, and poor conductivity lead to its poor capacitance and electrocatalytic activity. Herein, hierarchical Ti3C2Tx/MoS2/Ti3C2Tx@CC (TMT@CC) composites were well-designed as electrodes for both HER and supercapacitors. Flexible TMT@CC electrodes with an area as large as ∼ 80 cm2 and optimal mass-loading of 17.9 mg cm−2 were achieved. The inner layer Ti3C2Tx in the composites provides ideal nucleation sites for the growth of MoS2 arrays, and the outermost Ti3C2Tx effectively anchors the vertically arrayed MoS2. The hierarchically vertical structure provides strong interfacial coupling and shortens ion diffusion paths, leading to high stability and fast ion/electron transport kinetics. Due to such a synergistic effect, the flexible binder-free TMT@CC electrodes exhibited high areal capacitance (5.06 F cm−2 at 5 mA cm−2) for supercapacitors and low overpotential (119 mV versus RHE at 10 mA cm−2) for HER catalyst. Furthermore, a high energy density of 0.125 mWh cm−2 at a power density of 1.5 mW cm−2 has been achieved from the TMT@CC-based symmetric supercapacitor. Our strategy can be expanded to other vertically arrayed hierarchical structures as electrode materials of efficient HER and supercapacitors.