HIGHLIGHTS • The traditional and novel etching methods are summarized and compared, especially fluorine-free method. The methods for accelerating exfoliation of Ti 3 C 2 T x are classified. • The energy storage mechanisms of Ti 3 C 2 T x in different electrolytes are compared. Based on energy storage mechanisms, the influencing factors of morphology and surface functional groups are discussed.

Molybdenum disulfide (MoS 2 ) has become one of the most promising non-platinum-based electrocatalysts for the hydrogen evolution reaction (HER) because of its unique layered structure. However, the catalytic performance of the thermodynamically stable MoS 2 is hindered by its poor conductivity and scarce active sites. We developed a 3D porous N-doped graphene derivative-integrated metal−semiconductor (1T-2H) mixed phase MoS 2 (MNG) using urea as a doping reagent. The highly exposed active sites were achieved by inducing the phase transition of MoS 2 from 2H phase to 1T phase and the inclusion of highly N-incorporated reduced graphene oxide, both of which were simultaneously realized by optimizing the concentration of the doping reagent. Moreover, the charge/proton transfer was enhanced by the well-designed porous architecture and hydrophilic 1T-MoS 2 . With these advantages, the optimized MNG-40 catalyst has a small overpotential of 157 mV at a cathodic current density of 10 mA cm −2 , a relatively low Tafel slope of 45.8 mV dec −1 , and an excellent stability. This work represents a new strategy to design higher-performance HER catalysts and provides new insights into the structural regulation of metal composite transitions.

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Many efforts have been made to pursue low‐cost and efficient electrocatalysts for the hydrogen evolution reaction (HER), which is important for real water splitting applications. Herein, a 3D hydrogen evolution cathode is designed and synthesized by in situ grafting MoS2 nanosheets on a 3D carbon fiber felt (CFF) framework. As a low‐cost HER catalyst, MoS2 nanosheets have effective hydrogen atom adsorption activity due to their uniform distribution in the 3D CFF framework. Meanwhile, the 3D CFF framework facilitates the electrolyte to penetrate into the inner space and accelerate the electron transfer, which leads to a drastic increase in the HER activity. Electrochemical measurements show that the MoS2/CFF composite exhibit an excellent electrocatalytic activity with 101 mV overpotential, affording a current density of 10 mA cm−2 and a high exchange current density of 3.3 × 10−2 mA cm−2. Therefore, this 3D material, which has splendid catalytic performance and stability, exhibits great potential in the electrocatalytic hydrogen production for water splitting.

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