(561g) Enhanced Catalysis By Optical Nanoantenna Reduced on Monolayer Transition Metal Dichalcogenide

Enhanced Catalysis by
Optical Nanoantenna Reduced on Monolayer Transition Metal Dichalcogenide

D. Keith Roper^a,b*_,Jeremy R. Dunklin^c, Gregory T. Forcherio^d, Alexander O’Brien^a

^aDepartment of Chemical Engineering, University of
Arkansas, Fayetteville, AR 72701

^bMicroelectronics and Photonics
Graduate Program, University of Arkansas, Fayetteville, AR 72701        

^cNational Renewable Energy
Laboratory, Golden, CO 80401

^dArmy Research
Laboratory, Adelphia, MD 20783

Heterostructures
of two-dimensional (2D) transition metal dichalcogenide (TMD) and optical
nanoantenna (NA) offer optoelectronic inducibility with superior electron
mobility and gate tunability.  This enables enhanced photocatalytic activity of
interest for chemical and biological catalysis, energy, sensing,desalination,and nanoelectromechanical systems. However, characterization of
interrelated electro-optical and thermal effects at TMD-NA heterointerfaces is predominantly
empirical. Simulation and its integration with microscopic and spectroscopic
analysis of TMD-NA has been limited to date by complexity and convolution of
effects, particularly for characterizing dynamic interactions at nanometer (nm)
scales. Compact, multi-scale, integrated analysis of optical, electronic and
catalytic effects could identify extraordinary features to guide design and implementation.

This work compared simulated vs. measured optical, electronic,
and spectrocopic properties of TMD-NA for photoreductive catalysis.  Heterostructures
of monolayer (1L) TMD and NA were self-assembled via exfoliation and redox
chemistry (Fig 1). Nanometer- and femtosecond-resolved electron energy loss
spectroscopy (EELS) was used to simulate and measure low-energy NA plasmon
modes, damping and electric near fields at heterointerfaces (Fig 2).  Discrete
dipole approximation (DDA) was used to analyze transmission ultraviolet-visible
(TUV-vis) extinction spectra (Fig 3).  Heterostructures of 1LTMD-NA were tested
as catalyst electrodes for hydrogen evolution reaction using linear sweep
voltammography.

Transmission electron microscopy (TEM; Fig 1) and
x-ray photoelectron spectroscopy (XPS) showed NA were reduced directly onto
1LTMD flake edges forming covalent Au-sulfur bonds, the first such reported
result.  EELS (Fig 2) showed enhanced plasmon damping attributable to direct
electron transfer at the catalytic 1LTMD-NA heterointerface.  DDA (Fig 3)
revealed plasmon and exciton features enhanced in far field extinction spectra
of 1LTMD-NA heterostructures.  Photocatalytic reaction rates measured for these
novel 1LTMD-NA were over 10-fold higher than those reported for other TMD-based
electrodes.

This integration of novel experimental, computational,
microscopic and spectroscopic results leads to a new paradigm for improved
photocatalysis at 1LTMD-NA interfaces.  These new tools and data support
improved design of 1LTMD-NA photocatalysts and their implementation in a
variety of chemical, biological, energy and water systems.

[1] J.R. Dunklin, D.K.
Roper et al., in preparation. [2] G.
T. Forcherio, J.R. Dunklin, D.K. Roper et al., in submission.  [3] J.R.
Dunklin, D.K. Roper et al., in preparation.