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A miniature solar device for overall water splitting consisting of series-connected spherical silicon solar cells.

Kageshima Y, Shinagawa T, Kuwata T, Nakata J, Minegishi T, Takanabe K, Domen K - Sci Rep (2016)

Bottom Line: Impacts of the configuration on the PV module performance were carefully analyzed, revealing that a drastic increase in the photocurrent (≈20%) was attained by the effective utilization of a reflective sheet.Separate investigations on the electrocatalyst performance showed that non-noble metal based materials with reasonably small sizes (<0.80 cm(2)) exhibited substantial currents at the PV working voltage.By combining the observations of the PV characteristics, light management and electrocatalyst performance, solar-driven overall water splitting was readily achieved, reaching solar-to-hydrogen efficiencies of 7.4% (3PVs) and 6.4% (4PVs).

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.

ABSTRACT
A novel "photovoltaics (PV) + electrolyzer" concept is presented using a simple, small, and completely stand-alone non-biased device for solar-driven overall water splitting. Three or four spherical-shaped p-n junction silicon balls were successfully connected in series, named "SPHELAR." SPHELAR possessed small projected areas of 0.20 (3PVs) and 0.26 cm(2) (4PVs) and exhibited working voltages sufficient for water electrolysis. Impacts of the configuration on the PV module performance were carefully analyzed, revealing that a drastic increase in the photocurrent (≈20%) was attained by the effective utilization of a reflective sheet. Separate investigations on the electrocatalyst performance showed that non-noble metal based materials with reasonably small sizes (<0.80 cm(2)) exhibited substantial currents at the PV working voltage. By combining the observations of the PV characteristics, light management and electrocatalyst performance, solar-driven overall water splitting was readily achieved, reaching solar-to-hydrogen efficiencies of 7.4% (3PVs) and 6.4% (4PVs).

No MeSH data available.


Related in: MedlinePlus

Photographs of SPHELAR devices.(a) The series connected spherical silicon solar cells molded in transparent resin with 3.2 mm of diameter (SPHELAR, Kyosemi co. ltd.), the three series of silicon (3PVs, upper) and four series of silicon (4PVs, bottom), whose lengths of the body were approximately 0.7 and 0.9 cm, respectively, (b) the stand-alone module of 3PVs with electrocatalysts of minimized surface area. Scale: mm, and (c) schematic diagrams for SPHELAR module.
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f1: Photographs of SPHELAR devices.(a) The series connected spherical silicon solar cells molded in transparent resin with 3.2 mm of diameter (SPHELAR, Kyosemi co. ltd.), the three series of silicon (3PVs, upper) and four series of silicon (4PVs, bottom), whose lengths of the body were approximately 0.7 and 0.9 cm, respectively, (b) the stand-alone module of 3PVs with electrocatalysts of minimized surface area. Scale: mm, and (c) schematic diagrams for SPHELAR module.

Mentions: In this report, a stand-alone and integrated PV device consisting of nickel-based electrocatalysts and a “SPHELAR” solar module46 was investigated as an efficient, compact, and scalable “PV + electrolyzer” water splitting system. The SPHELAR modules were composed of either three or four series-connected silicon balls protected with a polymer (3PVs or 4PVs; 0.20 cm2 and 0.26 cm2 for the projected surface area, respectively) as shown in the schematic diagrams of Fig. 1, which provided a sufficient working voltage for water electrolysis (1.5–2.0 V). The PV device was investigated in various configurations, i.e., SPHELAR fixed within or above the electrolyte solution and with or without a proper reflector. Based on these comprehensive configuration evaluations, a theoretical optimization of the electrocatalyst surface area and a proposal of a possible device design were addressed. We also discussed the physical properties associated with the separation of the evolved hydrogen and oxygen gases in the membrane-less system with an appropriate design of the whole apparatus. Our detailed electrochemical study showed that the non-noble metal-based electrodes (NiMo for the cathode and NiFe for the anode) provided a sufficiently high current at an alkaline pH for the 3PV configuration. Additionally, with NiCoOx as the anode, a sufficient current for the 4PV configuration was achieved at a near-neutral pH. The presented device made from cost-effective materials exhibited STH efficiencies higher than 7%. This study was able to clearly demonstrate a novel approach to generate hydrogen by harvesting sunlight effectively with the completely stand-alone device.


A miniature solar device for overall water splitting consisting of series-connected spherical silicon solar cells.

Kageshima Y, Shinagawa T, Kuwata T, Nakata J, Minegishi T, Takanabe K, Domen K - Sci Rep (2016)

Photographs of SPHELAR devices.(a) The series connected spherical silicon solar cells molded in transparent resin with 3.2 mm of diameter (SPHELAR, Kyosemi co. ltd.), the three series of silicon (3PVs, upper) and four series of silicon (4PVs, bottom), whose lengths of the body were approximately 0.7 and 0.9 cm, respectively, (b) the stand-alone module of 3PVs with electrocatalysts of minimized surface area. Scale: mm, and (c) schematic diagrams for SPHELAR module.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834539&req=5

f1: Photographs of SPHELAR devices.(a) The series connected spherical silicon solar cells molded in transparent resin with 3.2 mm of diameter (SPHELAR, Kyosemi co. ltd.), the three series of silicon (3PVs, upper) and four series of silicon (4PVs, bottom), whose lengths of the body were approximately 0.7 and 0.9 cm, respectively, (b) the stand-alone module of 3PVs with electrocatalysts of minimized surface area. Scale: mm, and (c) schematic diagrams for SPHELAR module.
Mentions: In this report, a stand-alone and integrated PV device consisting of nickel-based electrocatalysts and a “SPHELAR” solar module46 was investigated as an efficient, compact, and scalable “PV + electrolyzer” water splitting system. The SPHELAR modules were composed of either three or four series-connected silicon balls protected with a polymer (3PVs or 4PVs; 0.20 cm2 and 0.26 cm2 for the projected surface area, respectively) as shown in the schematic diagrams of Fig. 1, which provided a sufficient working voltage for water electrolysis (1.5–2.0 V). The PV device was investigated in various configurations, i.e., SPHELAR fixed within or above the electrolyte solution and with or without a proper reflector. Based on these comprehensive configuration evaluations, a theoretical optimization of the electrocatalyst surface area and a proposal of a possible device design were addressed. We also discussed the physical properties associated with the separation of the evolved hydrogen and oxygen gases in the membrane-less system with an appropriate design of the whole apparatus. Our detailed electrochemical study showed that the non-noble metal-based electrodes (NiMo for the cathode and NiFe for the anode) provided a sufficiently high current at an alkaline pH for the 3PV configuration. Additionally, with NiCoOx as the anode, a sufficient current for the 4PV configuration was achieved at a near-neutral pH. The presented device made from cost-effective materials exhibited STH efficiencies higher than 7%. This study was able to clearly demonstrate a novel approach to generate hydrogen by harvesting sunlight effectively with the completely stand-alone device.

Bottom Line: Impacts of the configuration on the PV module performance were carefully analyzed, revealing that a drastic increase in the photocurrent (≈20%) was attained by the effective utilization of a reflective sheet.Separate investigations on the electrocatalyst performance showed that non-noble metal based materials with reasonably small sizes (<0.80 cm(2)) exhibited substantial currents at the PV working voltage.By combining the observations of the PV characteristics, light management and electrocatalyst performance, solar-driven overall water splitting was readily achieved, reaching solar-to-hydrogen efficiencies of 7.4% (3PVs) and 6.4% (4PVs).

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.

ABSTRACT
A novel "photovoltaics (PV) + electrolyzer" concept is presented using a simple, small, and completely stand-alone non-biased device for solar-driven overall water splitting. Three or four spherical-shaped p-n junction silicon balls were successfully connected in series, named "SPHELAR." SPHELAR possessed small projected areas of 0.20 (3PVs) and 0.26 cm(2) (4PVs) and exhibited working voltages sufficient for water electrolysis. Impacts of the configuration on the PV module performance were carefully analyzed, revealing that a drastic increase in the photocurrent (≈20%) was attained by the effective utilization of a reflective sheet. Separate investigations on the electrocatalyst performance showed that non-noble metal based materials with reasonably small sizes (<0.80 cm(2)) exhibited substantial currents at the PV working voltage. By combining the observations of the PV characteristics, light management and electrocatalyst performance, solar-driven overall water splitting was readily achieved, reaching solar-to-hydrogen efficiencies of 7.4% (3PVs) and 6.4% (4PVs).

No MeSH data available.


Related in: MedlinePlus