Chongyi Ling

Transition Metal-Promoted V2CO2 (MXenes): A New and Highly Active Catalyst for Hydrogen Evolution Reaction

Developing alternatives to precious Pt for hydrogen production from water splitting is central to the area of renewable energy. This work predicts extremely high catalytic activity of transition metal (Fe, Co, and Ni) promoted two‐dimensional MXenes, fully oxidized vanadium carbides (V2CO2), for hydrogen evolution reaction (HER). The first‐principle calculations show that the introduction of transition metal can greatly weaken the strong binding between hydrogen and oxygen and engineer the hydrogen adsorption free energy to the optimal value ≈0 eV by choosing the suitable type and coverage of the promoters as well as the active sites. Strain engineering on the performance of transition metal promoted V2CO2 further reveals that the excellent HER activities can maintain well while those poor ones can be modulated to be highly active. This study provides new possibilities for cost‐effective alternatives to Pt in HER and for the application of 2D MXenes.

Nanosheet Supported Single-Metal Atom Bifunctional Catalyst for Overall Water Splitting

Nanosheet supported single-atom catalysts (SACs) can make full use of metal atoms and yet entail high selectivity and activity, and bifunctional catalysts can enable higher performance while lowering the cost than two separate unifunctional catalysts. Supported single-atom bifunctional catalysts are therefore of great economic interest and scientific importance. Here, on the basis of first-principles computations, we report a design of the first single-atom bifunctional eletrocatalyst, namely, isolated nickel atom supported on β12 boron monolayer (Ni1/β12-BM), to achieve overall water splitting. This nanosheet supported SAC exhibits remarkable electrocatalytic performance with the computed overpotential for oxygen/hydrogen evolution reaction being just 0.40/0.06 V. The ab initio molecular dynamics simulation shows that the SAC can survive up to 800 K elevated temperature, while enacting a high energy barrier of 1.68 eV to prevent isolated Ni atoms from clustering. A viable experimental route for the synthesis of Ni1/β12-BM SAC is demonstrated from computer simulation. The desired nanosheet supported single-atom bifunctional catalysts not only show great potential for achieving overall water splitting but also offer cost-effective opportunities for advancing clean energy technology.

Oxidation Mechanism and Protection Strategy of Ultrathin Indium Selenide: Insight from Theory

Ultrathin indium selenide (InSe), as a newly emerging two-dimensional material with high carrier mobility and a broad absorption spectrum, has been the focus of current research. However, the long-term environmental instability of atomically thin InSe seriously limits its practical applications. To develop an effective strategy to protect InSe, it is crucial to reveal the degradation mechanism at the atomic level. By employing density functional theory and ab initio molecular dynamics simulations, we provide an in-depth understanding of the oxidation mechanism of InSe. The defect-free InSe presents excellent stability against oxidation. Nevertheless, the Se vacancies on the surface can react with water and oxygen in air directly and activate the neighboring In-Se bonds on the basal plane for further oxidation, leading to complete degradation of InSe into oxidation products of In2O3 and elemental Se. Furthermore, we propose an efficient strategy to repair the Se vacancies by thiol chemistry. In this way, the repaired surface can resist oxidation from oxygen and retain the original high electron mobility of pristine InSe simultaneously.

Towards a Comprehensive Understanding of the Reaction Mechanisms Between Defective MoS2 and Thiol Molecules

Sulfur vacancies (SVs) inherent in MoS2 are generally detrimental for carrier mobility and optical properties. Thiol chemistry has been explored for SV repair and surface functionalization. However, the resultant products and reaction mechanisms are still controversial. Herein, a comprehensive understanding on the reactions is provided by tracking potential energy surfaces and kinetic studies. The reactions are dominated by two competitive mechanisms that lead to either functionalization products or repair SVs, and the polarization effect from decorating thiol molecules and thermal effect are two determining factors. Electron-donating groups are conducive to the repairing reaction whereas electron-withdrawing groups facilitate the functionalization process. Moreover, the predominant reaction mechanism can be switched by increasing the temperature. This study fosters a way of precisely tailoring the electronic and optical properties of MoS2 by means of thiol chemistry approaches.

Computation-Aided Design of Single-Atom Catalysts for One-Pot CO2 Capture, Activation, and Conversion

Lowering the concentration of CO2 in atmosphere is a global concern but yet remains one of the most challenging processes in chemistry. Herein, we report a rational design of single-atom catalyst (SAC), namely, vanadium atom supported on newly synthesized β12 boron monolayer (V1/β12-BM), for one-pot CO2 capture, activation, and efficient conversion into methanol. Our first-principles computations reveal that strong interaction ensures V1/β12-BM can capture CO2 at ambient and elevated temperatures. Substantial charge transfer between V1/β12-BM and CO2 triggers the activation of CO2 into anionic CO2-, which can be efficiently hydrogenated into CH3OH with an ultralow limiting potential of 0.54 V and a rather low rate-determining barrier of 1.04 eV. Moreover, the adsorption of H2O molecules can make the reaction intermediates closer to the hydrogen source by the steric hindrance, which plays a key role in lowering the reaction barrier. Our findings present the first SAC for one-pot CO2 capture, activation, and conversion, which may open a new avenue for recycling CO2.

Molybdenum sulfide clusters immobilized on defective graphene: a stable catalyst for the hydrogen evolution reaction

Molybdenum sulfide is an intensely attractive noble-metal-free electrocatalyst for the hydrogen evolution reaction (HER). How to enhance electrical conductivity and maintain high intrinsic activity and active site density remains a challenge. Herein, we design a novel composite catalyst, which is composed of molybdenum sulfide clusters and defective graphene, holding excellent intrinsic activity, high-density active sites and high conductivity simultaneously. The strong S–C covalent bonds between clusters and graphene ensure the structural stability of the composite, avoiding the long-standing deactivation problem caused by cluster desorption. The clusters possess high-density active sites and the graphene acts as the conducting path to transport electrons from the electrode to active sites efficiently. Moreover, the simulations of diffusion of clusters on defective graphene demonstrate that the composite catalyst is easy to synthesize by a simple drop-casting procedure.