First-Principles Research On Molybdenum Disulfide-based Water Electrolysis Catalyst

Among various energy substitution strategies,the energy strategy with hydrogen as the main energy carrier will help realize a safe and clean energy future.Therefore,the effective production of hydrogen has become a key issue in the hydrogen economy.Among them,water splitting,one of the three main industrial hydrogen production methods,has attracted attention because it only needs water as a raw material,and the product is pollution-free.At present,the biggest problem facing the electrolysis of water for hydrogen production is low conversion efficiency and high energy consumption.Therefore,developing high-efficiency catalysts to reduce the overpotential of the cathode and anode has become a top priority.At present,for the cathode hydrogen evolution reaction(HER),the Pt-based catalyst has the highest catalytic activity;in the anode oxygen evolution reaction(OER),the noble metal-based catalysts such as RuO2 and IrO2 still have the highest catalytic activity.However,the high cost and limited earth reserves of the noble metal catalyst limits their commercial application.Therefore,it has become a research hotspot to find a cheap and efficient electrolysis water catalyst.Among many catalysts,MoS2-based catalysts have low cost and high catalytic activity,and are considered to be one of the representatives of alternative Pt catalysts.The traditional catalyst design method that relies on trial and error method wastes manpower and material resources,and the efficiency of finding high-efficiency catalysts is also very low.Nowadays,with the improvement of computer performance,it is possible to build a suitable calculation model through the computer,construct a catalyst structure-activity relationship based on a series of activity descriptors,and then predict the catalytic performance based on the structure-activity relationship,which provides more convenient and efficient catalyst design method.In this paper,aimed to develop a high-efficiency electrolysis water catalyst theoretical design method,density functional theory(DFT)is used to establish the relationship between the electronic structure,the adsorption energy of the intermediate product and a series of geometric properties of the two-dimensional MoS2-based catalyst.And the factors that can evaluate the catalytic activity of the electrolyzed water catalyst are found according to the proportional relationship.Finally,according to the structure information around the active site and the available physical and chemical properties,the structure-activity relationship of the two-dimensional MoS2-based catalyst based on the structure descriptor is summarized.Using the established structure-activity relationship,the catalytic activity trend can be accurately reproduced without the need for time-consuming quantitative calculations and simulations,and then high-throughput catalysts with excellent performance can be predicted.The main research contents are as follows:1.For the purpose of triggering OER performance and maintaining HER performance,28 single transition-metal(TM)supported on MoS2 edges as bifunctional electrocatalysts for overall water splitting has been screened by using DFT calculations.In order to design and achieve high OER performance,a simple equation derived from the chemical environment and local structure of the active center is used as a structure descriptor to predict the OER activities of MoS2-based single atom catalysts(SACs).Among these candidates,the T1-vacancy termination modified by Pt single atom shows the lowest theoretical overpotential for hydrogen/oxygen evolution reaction being just-0.10/0.46 V,respectively,which is comparable to those of the precious-metal-group benchmark catalysts for overall water splitting.It is expected that our results can offer a theoretical basis for simplifying and steering the design of efficient electrocatalytic materials.2.The HER activity on etched anti-triangular MoS2 are investigated by DFT calculations.We find the valence electron distribution of inner edge atoms can be affected by the corner,and accordingly determine their activity.The second-nearest atom to anti-triangular corner possesses the highest activity.The simulated polarization curves show etched anti-triangular Mo-edge MoS2 with moderate size(around 12 ?)maximize the HER performance.Further increasing size of etched MoS2 deactivate their HER activity to a certain degree,validated by available experimental data.This work suggests etched MoS2 catalysts with rational design may be a candidate to substitute Pt electrodes as HER electrocatalyst.3.Kinetic or thermodynamic methods based on DFT calculations are used to screen nearly 30 different non-metallic single-doped or double-doped two-dimensional MoS2 as electrocatalysts for alkaline HER.Among these candidates,MoS2 plane modified by B and Te shows the lowest theoretical overpotential for alkaline HER being just 0.28 V,which is lower than that of the benchmark Pt catalysts.Simultaneously,a new solo activity descriptor?EH*+OH*has been found in basic HER for single non-metallic doping system and even more for the bi-nonmetallic catalysts on which the desorption of OH*is more difficult.On this basis,the structural descriptor that is convenient for experimenters to directly refer to is developed.It is expected that our results will provide a new basic HER catalyst screening strategy and help us to quantify and efficiently screen electrocatalysts.4.Based on DFT calculations,MoS2 with coexistence of vacancies and non-metals is screened as the HER electrocatalyst at full pH.Among these candidates,we find that the two-dimensional MoS2 plane modified by Sv and Te has the best HER performance.The theoretical overpotential in acidic and alkaline electrolyte is only-0.03V and 0.65 V,respectively,which is lower than that of the benchmark Pt catalyst.Among them,vacancies play a very important role in catalyzing HER under both acidic and basic conditions because suitable defect states.Te plays a modifying role and coordinates the improvement of HER performance.At the same time,we further apply the descriptors and find that the vacancy-nonmetal coexistence system also conforms to the volcano-like relationship,indicating the correctness of the activity descriptors we found.