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
Scientific contributions from the Hydrogen Research Center at Texas A&M, 1982–1987
TL;DR: In this paper, the first five years of the work at the Hydrogen Research Center set up by NSF at the Texas A&M University were reviewed, and the main goals of the Center were described as the economic production of hydrogen from water using light as the energy source.
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Recent advances of hydrogen production through particulate semiconductor photocatalytic overall water splitting
Journal ArticleDOI
Synthesis, crystal and electronic structure of a new ternary parkerite selenide Pt3Pb2Se2
Sishun Wang,Sishun Wang,Kejun Bu,Dong Wang,Chong Zheng,Xiangli Che,Xiangli Che,Zhen Han,Fuqiang Huang +8 more
TL;DR: A new ternary selenide, Pt3Pb2Se2, was successfully synthesized at 1123 K by using a traditional solid-state method as mentioned in this paper.
Journal ArticleDOI
The p-Inp semiconductor / electrolyte contact under depletion conditions: Impedance, reverse currents and photopotentials
TL;DR: In this paper, an extremely low and potential independent frequency dispersion of Csc of 0.4% per frequency decade was obtained (20 Hz-20 kHz) at the p-InP H2SO4 contact, where capacitance data for the semiconductor surface energy barrier height φB with and without platinum coating and for different doping densities were compared with data from photentials.
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