Directly visualizing carrier transport and recombination at individual defects within 2D semiconductors

Abstract

Two-dimensional semiconductors (2DSCs) are promising materials for a wide range of optoelectronic applications. While the fabrication of 2DSCs with thicknesses down to the monolayer limit has been demonstrated through a...

Hybrid scanning electrochemical cell microscopy-interference reflection microscopy (SECCM-IRM): tracking phase formation on surfaces in small volumes

“…Scanning electrochemical cell microscopy (SECCM) provides a powerful platform to create very well defined and consistent microscale and nanoscale-sized electrochemical cells on various substrates. 36,37 Since its inception, 38,39 SECCM, and the scanning micropipette contact method (SMCM) as an earlier variant was named, has been widely employed to investigate electrochemical processes at the nanoscale, revealing heterogeneous properties of many features of materials including 2D materials, 36,[40][41][42][43] nanotubes, 44,45 grain boundaries and crystallographic facets in electrodes and electrocatalysts, [46][47][48] single particles, [49][50][51][52][53] among a rapidly expanding range of applications. 37 For phase formation and phase change processes, the ability to confine electrochemical reactions to small volumes allows the investigation of a few or even single events.…”

Multi-dimensional designer catalysts for negative emissions science (NES): bridging the gap between synthesis, simulations, and analysis

“…Figures 6 B–6D illustrate some example applications of SECCM which demonstrate the power of this and related techniques for studying complex electrochemical systems ( Mefford et al., 2021 ; Hill and Hill, 2021 ; Choi et al., 2020 ). Figure 6 B shows the application of SECCM to interrogate the rates of the oxygen evolution reaction (OER) across μm-scale β-Co(OH) 2 particles.…”

“…2D photocatalysts (aka 2-periodic) based on metal chalcogenides (e.g. MoS 2 , SnS 2 , WSe 2 , Bi 2 S 3 , Chevrel phases, to mention a few) ( Rahman et al., 2016 ; Degrauw et al., 2017 ; Ortiz-Rodríguez et al., 2020 ; Perryman et al., 2020a , 2020b ; Perryman and Velázquez, 2021 ; Hill and Hill, 2019 , 2021 ; Strange et al., 2020 ; Hill et al., 2020 ; Tolbert and Hill, 2021 ) and 2D metal halide perovskites ( Amerling et al., 2020 , 2021 ; Wu et al., 2021 ; Yuan et al., 2021 ; Pareja-Rivera et al., 2021 ) are well-suited materials for the reduction of CO 2 due to their strong light-matter interactions. Although many low-dimensional photocatalysts have a high density of electronically active sites for CO 2 binding, these same sites can act as recombination centers that detrimentally affect CO 2 conversion efficiencies.…”

“…The electrolyte contained 0.1 M NaI, 0.01 M I 2 . All images adapted with permission from the indicated sources ( Mefford et al., 2021 ; Choi et al., 2020 ; Hill and Hill, 2021 ). …”

“…In photocatalytic systems, the generation and transport of charge carriers which drive reactions will also play a critical role in the overall efficiency of a process. Figure 6 D illustrates how SECCM can be applied to visualize the generation and transport of charge carriers in semiconducting materials ( Hill and Hill, 2021 ). In this “carrier generation-tip collection” (CG-TC) mode, a localized excitation source, such as a focused laser, is utilized to generate carriers locally at a region of interest in a material.…”