Comparison of [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ as Electrocatalysts for H2 Production
Abstract
The complexes [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+, where PPh2NPh2 is 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane, are compared as electrocatalysts for H2 production under identical experimental conditions. With [(DMF)H]+ as the acid in acetonitrile solution, [Pd(PPh2NPh2)2]2+ afforded a turnover frequency (TOF) of 230 s-1 for formation of H2 under dry conditions and a TOF of 640 s-1 when H2O was added. These rates are similar to the TOF’s of 590 s-1 (dry) and 720 s-1 (wet) that were previously measured for [Ni(PPh2NPh2)2(CH3CN)]2+ using [(DMF)H]+. The [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ complexes both exhibited large current enhancements when treated with trifluoroacetic acid (TFA). At a TFA concentration of 1.8 M, TOF values of 5670 s-1 and 2060 s-1 were measured for [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+, respectively. The fast rates observed using TFA are, in part, attributed to homoconjugation of TFA in acetonitrile solutions, which decreases the effective pKa of the acid. In support of this hypothesis, dramatically lower rates of H2 production were observed using p anisidinium, which has a pKa comparable to TFA but does not homoconjugate significantly in acetonitrile solutions. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office ofmore »
- Authors:
- Publication Date:
- Research Org.:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Org.:
- USDOE
- OSTI Identifier:
- 1167646
- Report Number(s):
- PNNL-SA-99201
Journal ID: ISSN 0276-7333; KC0307010
- DOE Contract Number:
- AC05-76RL01830
- Resource Type:
- Journal Article
- Journal Name:
- Organometallics
- Additional Journal Information:
- Journal Volume: 33; Journal Issue: 18; Journal ID: ISSN 0276-7333
- Publisher:
- American Chemical Society
- Country of Publication:
- United States
- Language:
- English
- Subject:
- proton relay; electrocatalysis; hydrogen production
Citation Formats
Wiedner, Eric S., and Helm, Monte L. Comparison of [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ as Electrocatalysts for H2 Production. United States: N. p., 2014.
Web. doi:10.1021/om4010669.
Wiedner, Eric S., & Helm, Monte L. Comparison of [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ as Electrocatalysts for H2 Production. United States. https://doi.org/10.1021/om4010669
Wiedner, Eric S., and Helm, Monte L. 2014.
"Comparison of [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ as Electrocatalysts for H2 Production". United States. https://doi.org/10.1021/om4010669.
@article{osti_1167646,
title = {Comparison of [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ as Electrocatalysts for H2 Production},
author = {Wiedner, Eric S. and Helm, Monte L.},
abstractNote = {The complexes [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+, where PPh2NPh2 is 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane, are compared as electrocatalysts for H2 production under identical experimental conditions. With [(DMF)H]+ as the acid in acetonitrile solution, [Pd(PPh2NPh2)2]2+ afforded a turnover frequency (TOF) of 230 s-1 for formation of H2 under dry conditions and a TOF of 640 s-1 when H2O was added. These rates are similar to the TOF’s of 590 s-1 (dry) and 720 s-1 (wet) that were previously measured for [Ni(PPh2NPh2)2(CH3CN)]2+ using [(DMF)H]+. The [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ complexes both exhibited large current enhancements when treated with trifluoroacetic acid (TFA). At a TFA concentration of 1.8 M, TOF values of 5670 s-1 and 2060 s-1 were measured for [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+, respectively. The fast rates observed using TFA are, in part, attributed to homoconjugation of TFA in acetonitrile solutions, which decreases the effective pKa of the acid. In support of this hypothesis, dramatically lower rates of H2 production were observed using p anisidinium, which has a pKa comparable to TFA but does not homoconjugate significantly in acetonitrile solutions. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is oper-ated by Battelle for the U.S. Department of Energy.},
doi = {10.1021/om4010669},
url = {https://www.osti.gov/biblio/1167646},
journal = {Organometallics},
issn = {0276-7333},
number = 18,
volume = 33,
place = {United States},
year = {Mon Sep 22 00:00:00 EDT 2014},
month = {Mon Sep 22 00:00:00 EDT 2014}
}