Journal ArticleDOI
Hydrogen-evolving semiconductor photocathodes: nature of the junction and function of the platinum group metal catalyst
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In this paper, the Fermi level difference of p-InP and H/sup +//H/sub 2/ (0.9 +/- 0.2 eV) was shown to be a function of metal work functions.Abstract:
Noble metal incorporation in the surface of p-type semiconductor photocathodes to catalyze hydrogen evolution leads to efficient solar to chemical conversion if a set of energetic and kinetic criteria are satisfied: (1) the semiconductor-catalyst junction barrier height must be equal to or greater than that of the semiconductor H/sup +//H/sub 2/ junction; (2) the recombination velocity of photogenerated electrons at the semiconductor-catalyst interface must be low; (3) the overpotential for hydrogen evolution at solar cell current densities (approx.30 mA/cm/sup 2/) must be minor. Because of substantial differences in the vacuum work functions of Pt, Rh, Ru, and the (redox potential of the) H/sup +//H/sub 2/ couple, the barrier heights for junctions of each of the four systems with p-InP ought to vary widely. Yet experiments show that all p-InP(M)/H/sup +//H/sub 2/ junctions, where M = Pt, Rh, Ru, or no metal, have essentially the same approx.0.7-V gain in onset potential for hydrogen evolution relative to Pt/H/sup +//H/sub 2/. We attribute the similarity to the known lowering of metal work functions upon hydrogen alloying. Such alloying increases the barrier height and thereby the gain in onset potential over that anticipated from the vacuum work functions. The barrier height, measured as themore » limiting value of onset potential gain at high irradiance, approaches in all cases the Fermi level difference of p-InP and H/sup +//H/sub 2/ (0.9 +/- 0.2 eV). That Fermi level pinning by interfacial states is not the cause of the similar barriers is evident from the reversible decrease in onset potential with hydrogen depletion and by a unity diode perfection factor of the p-InP(Rh)/H/sup +//H/sub 2/ photocathode, which indicates no measurable interfacial recombination of photogenerated carriers. In agreement, the quantum efficiency of carrier collection (hydrogen evolution) nears unity.« lessread more
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Journal ArticleDOI
On the photoelectrocatalytic reduction of carbon dioxide
J. O'm. Bockris,J. C. Wass +1 more
TL;DR: In this paper, the authors examined the kinetics of photo-reduction of CO 2 in nonaqueous solutions containing tetraalkyl ammonium cations with special reference to the effects of surface decoration of p-CdTe with metals, organic complexes and crown ethers.
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State-of-the-art technologies for biofuel production from triglycerides: A review
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Colloidal polymerization of polymer-coated ferromagnetic cobalt nanoparticles into Pt-Co3O4 nanowires
Pei Yuin Keng,Mathew M. Bull,In Bo Shim,Kenneth G. Nebesny,Neal R. Armstrong,Younghun Sung,Kookheon Char,Jeffrey Pyun,Jeffrey Pyun +8 more
TL;DR: In this article, a functional 1D Pt-Co3O4 heterostruc-tures with enhanced electrochemical properties were synthesized via colloidal polymerization of polymer-coated ferromagnetic cobalt nanoparticles (PS-CoNPs).
Journal ArticleDOI
Thermochemical solar hydrogen generation.
TL;DR: In this article, a hybrid solar thermal/electrochemical process combines efficient photovoltaics and concentrated excess sub-bandgap heat into highly efficient elevated temperature solar electrolysis of water and generation of H2 fuel utilizing the thermodynamic temperature induced decrease of EH2O with increasing temperature.
Journal ArticleDOI
Efficient STEP (solar thermal electrochemical photo) production of hydrogen – an economic assessment
Stuart Licht,Stuart Licht,Olivia Chitayat,Harry Bergmann,Andrew Dick,Hina Ayub,Susanta Ghosh,Susanta Ghosh +7 more
TL;DR: In this paper, the economic viability of the STEP (Solar Thermal Electrochemical Photo) production of hydrogen fuel has been investigated, by comparing four different systems: (1) 10% or (2) 14% flat plate PV driven aqueous alkaline electrolysis H 2 production, (3) 25% CPV driven molten electrolysis hydrogen production, and (4) 35% concentrated photovoltaics driven solid oxide electrolysis (CPV driven H 2 ) production.
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