TMD-based highly efficient electrocatalysts developed by combined computational and experimental approaches.

As a large family of two-dimensional (2D) materials, transition metal dichalcogenides (TMDs) have been attracting an increasing level of attention and therefore considerable research input, owing to their intriguing catalytic, chemical and physical properties. The high exposed surface area, potentially large number of active sites, and chemical stability provide TMDs with vast opportunities for use as a unique class of electrocatalysts, while their low electrical conductivity and other deficiencies have drawn considerable research efforts for further modification. The optimization of TMDs can be achieved by several approaches, including site doping/modification, phase modulation, control of growth morphology and construction of heterostructures, by both appropriate computational simulations and purposely designed experimental studies. In tuning the TMD-based electrocatalysts, computational calculations have played uniquely important roles in predicting the structure and understanding the operational mechanism of catalytic performance. Indeed, the importance of refined calculations has been growing rapidly to provide comprehensive and unique guidance towards further modification of the existing TMD-based electrocatalysts and the discovery of new ones. In this critical review, we will look into the rapid advancement of the highly efficient TMD-based electrocatalysts that have been developed in recent years, achieved by combined computational and experimental approaches. Aiming to provide a generalized overall picture, we have conducted further computational studies as a systematic approach to unveil the modulation in the structure and the improvement in electrocatalytic properties brought in by appropriate element doping/modification in either basal plane A-(metal atoms) and B-(chalcogen atoms) sites or edge sites of the 2D TMD materials, as well as in some of those non-layered metal disulfides/diselenides. This review is concluded by summarizing the likely future development and perspectives of TMD-based electrocatalysts.

A High-Rate and Stable Quasi-Solid-State Zinc-Ion Battery with Novel 2D Layered Zinc Orthovanadate Array.

Zinc-ion batteries are under current research focus because of their uniqueness in low cost and high safety. However, it is still desirable to improve the rate performance by improving the Zn2+ (de)intercalation kinetics and long-cycle stability by eliminating the dendrite formation problem. Herein, the first paradigm of a high-rate and ultrastable flexible quasi-solid-state zinc-ion battery is constructed from a novel 2D ultrathin layered zinc orthovanadate array cathode, a Zn array anode supported by a conductive porous graphene foam, and a gel electrolyte. The nanoarray structure for both electrodes assures the high rate capability and alleviates the dendrite growth. The flexible Zn-ion battery has a depth of discharge of ≈100% for the cathode and 66% for the anode, and delivers an impressive high-rate of 50 C (discharge in 60 s), long-term durability of 2000 cycles at 20 C, and unprecedented energy density ≈115 Wh kg-1 , together with a peak power density ≈5.1 kW kg-1 (calculation includes masses of cathode, anode, and current collectors). First principles calculations and quantitative kinetics analysis show that the high-rate and stable properties are correlated with the 2D fast ion-migration pathways and the introduced intercalation pseudocapacitance.