Few-layer transition metal dichalcogenide alloys based on molybdenum sulphoselenides [MoS2(1-x)Se2x] possess higher hydrogen evolution (HER) activity compared to pristine few-layer MoS2 and MoSe2. Variation of the sulphur or selenium content in the parent dichalcogenides reveals a systematic structure-activity relationship for different compositions of alloys, and it is found that the composition MoS1.0Se1.0 shows the highest HER activity amongst the catalysts studied. The tunable electronic structure of MoS2/MoSe2 upon Se/S incorporation probably assists in the realization of high HER activity.

A layered MPS3-type compound, FePS3, is introduced as an electrocatalyst for hydrogen evolution reaction (HER). The non-noble metal-based FePS3 is a semiconductor that could be solvent exfoliated into few-layer, two-dimensional (2D) nanosheets. The 2D thin sheets exhibit very good catalytic activity and stability toward HER over a wide pH range of acidic, alkaline, phosphate buffer, and 3.5 wt % aqueous NaCl solutions. The Tafel slope and exchange current density in acidic medium are determined to be ∼(45–50) mV dec–1 and 1 ± 0.2 × 10–3 A cm–2, respectively. The stability of the catalyst is found to be very good. Density functional theory calculations reveal P and S as favorable hydrogen adsorption sites. This material opens up a new class of ternary, layered semiconductors for various electrocatalytic studies and might also become important from a device physics point of view.

There has been a spurt of activity in using layered MPX 3 (M = transition metal, X = chalcogen, S/Se/Te) compounds in various studies including catalysis and devices.In the present study, low band gap, ternary iron selenophosphate (FePSe 3 ) is introduced as an excellent and highly stable trifunctional electrocatalyst for hydrogen evolution, oxygen evolution, and oxygen reduction reactions. It is observed that the present catalyst is useful in evolving hydrogen over a wide pH range including seawater environment. Density functional theory calculations reveal various parameters that help improve the electrocatalytic activity of the layered material. Covalency of the Fe−Se bond, distortion in the crystal structure, and adsorption properties are shown to be responsible for the observed high catalytic activity.

Organic materials containing active carbonyl groups have attracted considerable attention as electrodes in Li-ion batteries due to their reversible redox activity, ability to retain capacity, and, in addition, their ecofriendly nature. Introduction of porosity will help accommodate as well as store small ions and molecules reversibly. In the present work, we introduce a mesoporous triptycene-related, rigid network polymer with high specific surface area as an electrode material for rechargeable Li-ion battery. The designed polymer with a three-dimensional (3D), rigid porous network allows free movement of ions/electrolyte as well as helps in interacting with the active anhydride moieties (containing two carbonyl groups). Considerable intake of Li ions giving rise to very high specific capacity of 1100 mA h g at a discharge current of 50 mA g and ∼120 mA h g at a high discharge current of 3 A g are observed with excellent cyclability up to 1000 cycles. This remarkable rate capability, which is one of the highest among the reported organic porous polymers to date, makes the triptycene-related rigid 3D network a very good choice for Li-ion batteries and opens up a new method to design polymer-based electrode materials for metal-ion battery technology.

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