TY - JOUR
T1 - Understanding and Controlling the Performance-Limiting Steps of Catalyst-Modified Semiconductors
AU - Nguyen, Nghi P.
AU - Wadsworth, Brian L.
AU - Nishiori, Daiki
AU - Reyes Cruz, Edgar A.
AU - Moore, Gary F.
N1 - Funding Information:
This work was supported by the National Science Foundation under Early Career Award 1653982 (polymeric surface chemistry) and by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Early Career Award DE-SC0021186 (light intensity experiments). G.F.M. acknowledges support from the Camille Dreyfus Teacher-Scholar Awards Program. B.L.W. was supported by an IGERT-SUN fellowship funded by the National Science Foundation (1144616) and the Phoenix Chapter of the ARCS Foundation. The authors gratefully acknowledge Diana Convey in the Goldwater Materials Science Facility at Arizona State University for assistance with ellipsometry measurements, Gwyneth Gordon in the Metals, Environmental and Terrestrial Analytical Laboratory at Arizona State University for assistance with ICP-MS measurements, Timothy Karcher in the Eyring Materials Center at Arizona State University for assistance with XPS data collection, and Michael Dodson in the Biodesign Institute at Arizona State University for assistance with contact angle measurements.
Publisher Copyright:
©
PY - 2021/1/14
Y1 - 2021/1/14
N2 - Understanding and controlling factors that restrict the rates of fuel-forming reactions are essential to designing effective catalyst-modified semiconductors for applications in solar-to-fuel technologies. Herein, we describe GaAs semiconductors featuring a polymeric coating that contains cobaloxime-type catalysts for photoelectrochemically powering hydrogen production. The activities of these electrodes (limiting current densities >20 mA cm-2 under 1-sun illumination) enable identification of fundamental performance-limiting bottlenecks encountered at relatively high rates of fuel formation. Experiments conducted under varying bias potential, pH, illumination intensity, and scan rate reveal two distinct mechanisms of photoelectrochemical hydrogen production. At relatively low polarization and pH, the limiting photoactivity is independent of illumination conditions and is attributed to a mechanism involving reduction of substrate protons. At relatively high polarization or pH, the limiting photoactivity shows a linear response to increasing photon flux and is attributed to a mechanism involving reduction of substrate water. This work illustrates the complex interplay between transport of photons, electrons, and chemical substrates in photoelectrosynthetic reactions and highlights diagnostic tools for better understanding these processes.
AB - Understanding and controlling factors that restrict the rates of fuel-forming reactions are essential to designing effective catalyst-modified semiconductors for applications in solar-to-fuel technologies. Herein, we describe GaAs semiconductors featuring a polymeric coating that contains cobaloxime-type catalysts for photoelectrochemically powering hydrogen production. The activities of these electrodes (limiting current densities >20 mA cm-2 under 1-sun illumination) enable identification of fundamental performance-limiting bottlenecks encountered at relatively high rates of fuel formation. Experiments conducted under varying bias potential, pH, illumination intensity, and scan rate reveal two distinct mechanisms of photoelectrochemical hydrogen production. At relatively low polarization and pH, the limiting photoactivity is independent of illumination conditions and is attributed to a mechanism involving reduction of substrate protons. At relatively high polarization or pH, the limiting photoactivity shows a linear response to increasing photon flux and is attributed to a mechanism involving reduction of substrate water. This work illustrates the complex interplay between transport of photons, electrons, and chemical substrates in photoelectrosynthetic reactions and highlights diagnostic tools for better understanding these processes.
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U2 - 10.1021/acs.jpclett.0c02386
DO - 10.1021/acs.jpclett.0c02386
M3 - Article
C2 - 33325709
AN - SCOPUS:85099025404
SN - 1948-7185
VL - 12
SP - 199
EP - 203
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 1
ER -