Unravelling Rashba-Dresselhaus Splitting Assisted Magneto-Photoelectrochemical Water Splitting in Asymmetric MoSSe-GaN Heterostructures

Abstract

Among two-dimensional (2D) materials, asymmetric Janus structures (MoSSe, WSSe) have many exciting properties, such as out-of-plane piezoelectricity, spatial isolation of charge carriers, and strong spin−orbit coupling (SOC), resulting in a significant Rashba effect. However, the experimental validation to utilize SOC along with advanced optical properties for catalytic applications remains unexplored. Herein, for the first time, we demonstrate a proof-of-concept for spin-manipulated photo-electrochemical water splitting using Janus MoSSe/GaN heterostructures under an external low magnetic field. Further, the activation with delaminated 2D-MXene (Ti 3 C 2 T x /MoSSe/GaN) for efficient electron channeling manifests ∼1.37 times photocurrent enhancement and ∼1.50-fold enhancement in product (H 2 /O 2 ) formation under a low applied magnetic field (0.4 T). The external magnetic field supports spin manipulation even under unpolarized light by a spin-to-charge conversion in Janus MoSSe/GaN heterostructures. Density functional theory simulations were performed to understand the role of the Rashba-Dresselhaus effect for efficient charge transport.

Giant and tunable Rashba spin splitting and quantum spin Hall effect in H-Pb-Cl

“…随着拓扑绝缘体(Topological Insulator，TI)的兴起与被广泛深入的研究 [1] ，自旋轨道 耦合(Spin-Orbit Coupling，SOC)引起了人们极大的兴趣。SOC 来源于电子的自旋与其在 电场中的运动之间的相互作用。根据相对论理论，当静止参考系中的电子在电场中运动时， 通过相对论的洛伦兹变换，电子会感受到一个和电场以及电子运动有关的等效磁场。这个等 效磁场和电子自旋的 Zeeman 相互作用将电子的自旋和轨道运动耦合在一起，即 SOC [2,3] 。 SOC 作用的强度与构成材料原子的原子序数密切相关，电子平均速度较高的重原子，SOC 的强度更大。对于研究电子自旋行为的自旋电子学，SOC 效应提供了控制电子自旋的可能 性，进而可以在具有强 SOC 作用的材料中诱发一系列新奇的特性，如自旋弹道输运 [4] 、电 流诱导的自旋极化 [5] 、自旋电流效应 [6] 、超冷原子 [7][8][9][10][11] 、量子电路 [12][13][14][15] 等等。在所有的与 SOC 有关的现象中，由结构空间反演对称性破缺导致的 Rashba 类型自旋劈裂和量子自旋霍尔效 应(Quantum Spin Hall Effect，QSHE)最受关注。 对于 Rashba 类型的 SOC 劈裂，由于其最容易被外电场调控 [3,16] ，且经常与材料内部反 演对称性破缺导致的 Dresselhaus 型的自旋轨道耦合纠缠在一起 [17][18][19][20] ，在材料的电子性质上 诱导出现各向异性的自旋劈裂，进而出现一系列有趣的物理现象。此外，Rashba 类型的 SOC 在实现无需外磁场作用的自旋电子器件方面具有很大的应用前景，且巨型可调控的 Rashba 自旋劈裂更是对自旋场效应晶体管的实现具有重要意义。在实际的操作中，由于 SOC 诱导 的 Rashba 效应和自旋电子器件的工作温度高度依赖于 SOC 的强度 [21,22] ，因此实际的自旋电 子应用对具有强 Rashba 自旋轨道耦合的材料有很高的需求。早期的研究中，人们发现可以 在重金属的表面 [23][24][25][26] 或者合金表面 [27][28][29][30][31] 诱导出较大的 Rashba 效应 [32] ， 但它们由于缺乏带隙， 不能广泛应用于许多自旋电子学器件 [33] 。在体半导体和铁电体系统 [34][35][36][37][38][39][40] 中也发现了巨大的 体 Rashba 效应，这种效应甚至可以通过外部电场进行切换 [41]…”

Rashba effect: a chemical physicist's approach

“…13,43,44 Current research continues to explore the development of surface modifications. [45][46][47][48][49][50] However, it also delves into GSS induced in novel 2D layered materials, including transition-metal dichalcogenides (TMDs), [51][52][53][54][55][56][57] MXenes, [58][59][60][61][62][63] and a variety of other sheets. [64][65][66][67][68][69][70][71][72] To facilitate the ongoing efforts, it is crucial to develop more robust strategies for enhancing spin splitting.…”

“…13,43,44 Current research continues to explore the development of surface modifications. 45–50 However, it also delves into GSS induced in novel 2D layered materials, including transition-metal dichalcogenides (TMDs), 51–57 MXenes, 58–63 and a variety of other sheets. 64–72…”

Enhanced hydrogen evolution reaction via photoelectrochemical water splitting utilizing asymmetric MoSSe under a low external magnetic field

“…35–37 Second, to study the spin properties exclusively of MoSSe (Rashba and Zeeman splitting) under an external magnetic field in photoexcited charge carrier separation without any such effect from the substrate, unlike the Rashba–Dresselhaus effect in combination with the GaN substrate in our previous report. 23 Third, expensive GaN was replaced by silicon to introduce a cost-effective device strategy. Therefore, this is a striking matter to look at how the spin properties of asymmetric MoSSe along with its excellent photocatalytic, 38,39 electrocatalytic 4 and excitonic 8,9 properties together address the issue of the lower efficiency of PEC hydrogen evolution reaction through water splitting under an external magnetic field with a suitable heterostructure.…”