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This content will become publicly available on April 30, 2019

Title: Interface engineering of colloidal CdSe quantum dots thin films as acid-stable photocathodes for solar-driven hydrogen evolution

Colloidal semiconductor quantum dots-based (CQD) photocathodes for solar-driven hydrogen evolution have attracted significant attention due to their tunable size, nanostructured morphology, crystalline orientation, and band-gap. Here, we report a thin film heterojunction photocathode composed of organic PEDOT:PSS as a hole transport layer, CdSe CQDs as a semiconductor light absorber, and conformal Pt layer deposited by atomic layer deposition (ALD) serving as both a passivation layer and cocatalyst for hydrogen evolution. In neutral aqueous solution, a PEDOT:PSS/CdSe/Pt heterogeneous photocathode with 200 cycles of ALD Pt produces a photocurrent density of -1.08 mA/cm 2 (AM1.5G, 100 mW/cm 2) at a potential of 0 V vs. RHE (j 0) in neutral aqueous solution, which is nearly 12 times that of the pristine CdSe photocathode. This composite photocathode shows an onset potential for water reduction at +0.46 V vs. RHE and long-term stability with negligible degradation. In acidic electrolyte (pH = 1), where the hydrogen evolution reaction is more favorable but stability is limited due to photocorrosion, a thicker Pt film (300 cycles) is shown to greatly improve the device stability and a j 0 of -2.14 mA/cm 2 is obtained with only 8.3% activity degradation after 6 h, compared to 80% degradation undermore » the same conditions when the less conformal electrodeposition method is used to deposit the Pt layer. Electrochemical impedance spectroscopy and time-resolved photoluminescence results indicate that these enhancements stem from a lower bulk charge recombination rate, higher interfacial charge transfer rate, and faster reaction kinetics. In conclusion, we believe that these interface engineering strategies can be extended to other colloidal semiconductors to construct more efficient and stable heterogeneous photoelectrodes for solar fuel production.« less
Authors:
 [1] ;  [2] ;  [1] ;  [1] ; ORCiD logo [3] ;  [4] ;  [1] ;  [1] ;  [5] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Wake Forest Univ., Winston-Salem, NC (United States)
  2. Harbin Institute of Technology, Shenzhen (China)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. IBM TJ Watson Research Center, Yorktown Heights, NY (United States)
  5. Soochow Univ., Jiangsu (China)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Name: ACS Applied Materials and Interfaces; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; interface engineering; colloidal quantum dots; atomic layer deposition; photocathode; hydrogen evolution
OSTI Identifier:
1436031