Energy implications of future stabilization of atmospheric CO2 content

Hoffert, Martin I.; Caldeira, Ken; Jain, Atul K.; Haites, Erik; Harvey, L. D. Danny; Potter, Seth; Schlesinger, Michael E.; Schneider, Stephen H.; Watts, Robert G.; Wigley, T. M. L.; Wuebbles, Donald J.

doi:10.1038/27638

Cited by 582 publications

(418 citation statements)

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“…While there GHG concentrations in the atmosphere. An early proposed target was stabilization of atmospheric GHG concentrations [52][53][54] , and some still advocate such a target (for example, the nongovernmental movement 350.org). GHG concentrations are well-observed, however, impacts do not track them closely.…”

Section: Global Warming and Local Climate Change Impactsmentioning

confidence: 99%

A scientific critique of the two-degree climate change target

et al. 2015

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Section: Global Warming and Local Climate Change Impactsmentioning

confidence: 99%

A scientific critique of the two-degree climate change target

et al. 2015

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“…The world's demand for energy is projected to double by 2050 in response to population growth and the industrialization of developing countries. 1 The supply of fossil fuels is limited, with restrictive shortages of oil and gas projected to occur within our lifetimes (see the article by Paul Weisz in PHYSICS TODAY, July 2004, page 47). Global oil and gas reserves are concentrated in a few regions of the world, while demand is growing everywhere; as a result, a secure supply is increasingly difficult to assure.…”

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confidence: 99%

The Hydrogen Economy

2004

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“…renewable | solar fuels | electrocatalysis S olar-to-fuels conversions provide a path to harnessing the ubiquitous albeit intermittent renewable energy resource offered by the sun (1)(2)(3)(4)(5)(6). Efficient catalysis of transformations of energy consequence (7)(8)(9)(10)(11)(12)(13) mandates the coupling of electron transfer (ET) to proton transfer (PT) in proton-coupled electron transfer (PCET) reactions (14)(15)(16)(17)(18)(19)(20).…”

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Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

Bediako

Solis

Dogutan

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

189

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The hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We conclude that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer-electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring.renewable | solar fuels | electrocatalysis S olar-to-fuels conversions provide a path to harnessing the ubiquitous albeit intermittent renewable energy resource offered by the sun (1-6). Efficient catalysis of transformations of energy consequence (7-13) mandates the coupling of electron transfer (ET) to proton transfer (PT) in proton-coupled electron transfer (PCET) reactions (14)(15)(16)(17)(18)(19)(20). In the absence of PCET, intermediates possessing equilibrium potentials that are prohibitively large depreciate the storage capacity offered by the solarto-fuels conversion process. The coupling of protons to changes in electron equivalency offers the possibility of restricting the equilibrium potentials of the redox steps to a more narrow potential range, thereby minimizing the overpotential required to sustain catalysis at a desired turnover rate. Thus, the exploitation of PCET pathways to permit potential-leveling effects is a crucial prerequisite for the efficient catalytic conversion reactions of energy relevant molecules.PCET reactions may be classified into stepwise and concerted pathways (14,16,20,21). Stepwise PCET may involve ET first followed by PT (ETPT), or PT followed by ET (PTET). In concerted proton-electron transfers (CPET), the proton and electron traverse a common transition state. Whereas concerted pathways avoid the formation of thermodynamically costly intermediates, CPET reactions may incur kinetic penalties associated with the requirements for proton tunneling (19,20,22). The competition between these dynamics during catalysis determines the most efficient route of reaction. Studies that explore the interplay between these factors are crucial to designing catalytic reactions of high efficiency. Along these lines, the incorporation of proton relays in the second coordination sphere of molecular catalysts has emerged as a useful tool in optimizing PCET transformations (23-29). We have focused on the synthesis and mechanistic investigation of a class of me...

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Energy implications of future stabilization of atmospheric CO2 content

Cited by 582 publications

References 10 publications

A scientific critique of the two-degree climate change target

A scientific critique of the two-degree climate change target

The Hydrogen Economy

Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

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