PbS Electrode Research Articles

High‐performance counter electrode based on nitrogen‐doped porous carbon nanoribbons for quantum dot‐sensitized solar cells

Nitrogen-doped porous carbon nanoribbons (NPCNs) are facilely prepared by carbonization of polypyrrole (PPy) nanotubes followed by a chemical activation process. NPCN counter electrodes are subsequently fabricated by depositing NPCNs onto Ti mesh for quantum dot-sensitized solar cells (QDSCs). Electrochemical tests are carried out to evaluate the electrocatalytic performance of obtained NPCN electrode. The data of electrochemical tests suggest that the NPCN electrode has a superior electrocatalytic ability towards polysulfide (S22−/S2−) electrolyte regeneration reaction and displays a high stability in polysulfide electrolyte. The excellent electrocatalytic performance of NPCN electrode can be ascribed to their large surface area, 2D porous nanoribbon morphology, and nitrogen atom doping, which provides abundant electrocatalytic active sites and facilitates the electrolyte diffusion. Consequently, a power conversion efficiency of 3.27% is obtained by using NPCN electrode as the counter electrode for QDSC. This efficiency is close to the QDSC assembled with commonly used PbS electrode (4.0%).

Microflower-like nickel sulfide-lead sulfide hierarchical composites as binder-free electrodes for high-performance supercapacitors

Abstract Nickel sulfide (NiS), lead sulfide (PbS) and composite of NiS-PbS hybrid are deposited onto nickel (Ni) foam current collector via a simple and cost-effective chemical bath deposition route and utilized as a binder-free battery-type electrode materials for supercapacitor applications. High-performance NiS and highly-stable PbS electrodes are rationally designed to develop a new class NiS-PbS electroactive material. Surface morphological and structural studies indicate that the NiS-PbS composite exhibits a beautiful morphology of nanosheet based microflower structures. Such hierarchical microflower structures provide abundant Faradic active sites and enable the fast redox reactions. As result, the NiS-PbS composite exhibits a higher specific capacity of 125.89 mA h g−1 at a current density of 2 A g−1 in 3 M KOH electrolyte solution, and it is 1.62 and 2.67 times higher than the bare NiS and PbS electrodes. In addition, NiS-PbS composite delivers excellent cycling stability retaining 88.97% of initial capacitance after 3000 cycles, which is much larger than that of NiS (76.86%) and PbS (82.72%) electrodes. Our results demonstrate that the microflower structured NiS-PbS composites are promising for supercapacitor applications.

Controlled Prelithiation of PbS to Pb/Li2S for High Initial Coulombic Efficiency in Lithium Ion Batteries

PbS nanoparticle aggregates were synthesized in a simple aqueous reaction at room temperature, and were tested as a lithium ion anode material, with a gravimetric capacity of 374 mAh/g at C/2, and a 0.15% capacity loss per cycle. However, its half cell initial Coulombic efficiency (ICE) was only 40%, due to a combination of irreversible Li2S and solid electrolyte interface (SEI) formations. A custom controlled prelithiation technique was then applied to the PbS electrodes, converting the active material to Pb/Li2S, and consolidating the SEI prior to coin cell assembly. This brought the ICE from 40% to >97%, and allowed for immediate cycling of the electrode at high Coulombic efficiency, without further formation cycles. Upon construction of prelithiated Pb/Li2S vs NCM full cells, an 82% ICE was observed, with the majority of the lithium loss from the NCM. The full cells had a combined electrode capacity of 100 mAh/g at C/2.

(Invited) Photocurrent Enhancement of Quantum Dot Solar Cells By Plasmonic Metal Nanoparticles

Photocurrent Enhancement of Quantum Dot Solar Cells by Plasmonic Metal Nanoparticles Tetsu Tatsuma and Tokuhisa Kawawaki Institute of Industrial Science, University of Tokyo Komaba, Meguro-ku, Tokyo 153-8505, Japan Noble metal nanoparticles absorb and scatter visible and near infrared light on the basis of localized surface plasmon resonance (LSPR). We found plasmon-induced charge separation (PICS)1,2 at the interface between plasmonic metal nanoparticles and semiconductor such as TiO2 and applied it to photoelectrochemistry. Another way of application of LSPR to photoelectrochemistry is based on a plasmonic enhancement effect.3 We have also examined the plasmonic enhancement effect on dye-sensitized solar cells, and found that there is the optimum distance between plasmonic nanoparticles and dye molecules4 and that enhancement is possible in the near infrared region by taking advantage of a plasmon coupling effect.5 Here we report a plasmonic enhancement effect of metal nanoparticles on quantum dot solar cells. We prepared two-dimensional ITO/Au/TiO2/PbS electrodes.6 Au nanospheres were adsorbed onto a smooth ITO and coated them with a TiO2 thin film by a spray pyrolysis method. PbS quantum dots were prepared on the TiO2 surface using a successive ionic layer adsorption and reaction method through alternate spin-coating with aqueous Pb(NO3)2 and aqueous Na2S. Photocurrents were examined by using a two-electrode cell with the ITO/Au/TiO2/PbS electrode, a platinum-coated ITO counter electrode, and N2-saturated aqueous electrolyte containing Na2S. The photocurrents of the cell were enhanced in the wavelength range of 500-1200 nm by the Au nanospheres. The optimum quantum dot-nanosphere spacing was shorter and the maximum enhancement factor was higher when smaller quantum dots were used. This suggests that quenching via energy transfer from the PbS quantum dots to Au nanosphere is less significant for smaller quantum dots. We also electrodeposited Au nanostars on an ITO electrode and coated them with a ZnO thin film. The nanostars generate strong optical near field at the tips. It was possible to control the plasmonic enhancement peak wavelength in the visible and near-infrared region by changing the deposition time. In addition, we used Ag nanocubes for efficiency enhancement of a PbS quantum dot heterojunction cell. Ag nanocubes also generate strong optical near field at the corners and strong far field scattering. The location and amount of the nanocubes were optimized in terms of photocurrents and efficiency. This work was supported in part by “R&D on Innovative PV Power Generation Technology” which The University of Tokyo contracted with New Energy and Industrial Technology Development Organization (NEDO) and a Grant-in-Aid for Scientific Research.

Design and development of electronic- and micro-structures for multi-functional working electrodes in dye-sensitized solar cells

This paper outlines a new strategy to optimize the performance of electrodes in dye-sensitized solar cells (DSSCs), through the engineering of electronic structures in conjunction with the micro-structures of the devices. We propose a simple hydrolysis method for the fabrication of a family of quasi-core–shell TiO2 (hydrolysis)/PbS composites for working electrodes. Measurements confirm a shift in absorption from the UV to visible range. We also measured cell performance, including short-circuit photocurrent, open-circuit photovoltage, and the power conversion efficiency (η) of DSSCs. The obtained η of DSSC (6.05%) with a TiO2 (P-25)/TiO2 (hydrolysis)+0.005M PbS electrode is substantially higher than that of the conventional DSSC (5.11%) with a TiO2 (P-25) electrode, due to improved p–n junctions, light-scattering, and light absorption. Finally, the shell of TiO2 (hydrolysis) protected the core of PbS from the corrosive effects of electrolytes, thereby prolonging the life span of the DSSC. This novel approach to electrode design could lead to advances in DSSC as well as other energy applications including photo-catalysis technology.

Preparation of a Highly Efficient PbS Electrode and Its Application in Quantum Dots-Sensitized Solar Cells

To improve the light-to-electric conversion efficiency of quantum dots-sensitized nanocrystalline thin-film solar cells, a PbS electrode with high electrocatalytic activity toward polysulfide electrolyte was prepared by successively treating Pb foil in acid and polysulfide solutions. Electrochemical impedance spectroscopy(EIS)measurements were performed to evaluate the electrocatalytic activity of the prepared PbS electrode. Based on the EIS results, the temperature and time to treat the Pb foil in the acid solution were optimized. The PbS electrode prepared under the optimized conditions was used as a counter electrode to fabricate a quantum dotssensitized solar cell with a CdSe quantum dots-sensitized TiO2 nanocrystalline thin film as the photoanode and polysulfide solution as the electrolyte. Both the electrocatalytic activity and light-to-electric conversion properties of the PbS electrode prepared from acid treatment of Pb foil for the optimized temperature and time are superior to those of electrodes prepared by other reported methods. In our method, the treatment time is considerablyless but the PbS counter electrode maintains a superior catalytic activity compared with other methods. X-ray diffraction and scanning electron microscopy were performed to demonstrate the formation process of PbS,and the catalytic enhancement mechanism of the prepared PbS electrode is discussed.

Improved performance of CdS/CdSe quantum dot-sensitized solar cells using Mn-doped PbS quantum dots as a catalyst in the counter electrode

This study reports the enhanced catalytic ability of Mn-doped PbS QDs synthesized using a successive ionic layer adsorption and reaction (SILAR) method for quantum dot-sensitized solar cells (QDSSCs). Electrochemical and optical analysis of each material showed that the catalytic ability of the PbS electrode was improved significantly by Mn2+ doping. Two factors can explain this behavior. The first is that intentional impurities have an impact on the structure of the host material, such as increases in surface roughness. The other is that dopants create new energy states that delay the exciton recombination time and allow charge separation to be activated. As a result, the photoelectron supply from the counter electrode is accelerated, resulting in vigorous redox reactions at the polysulfide electrolyte. The performance of the CdS/CdSe QDSSC using a Mn-doped PbS counter electrode was compared with those using the Pt and PbS counter electrodes. Finally, a power conversion efficiency of 3.61% was achieved with the Mn-doped PbS counter electrode (VOC=0.61V, JSC=11.67mAcm−2, FF=0.51) under one sun illumination (100mWcm−2), which is ∼40% higher than that of CdS/CdSe QDSSCs with the bare PbS counter electrode.

Influence of highly efficient PbS counter electrode on photovoltaic performance of CdSe quantum dots-sensitized solar cells

PbS electrode with high catalytic activity to Sn 2− reduction certificated by the measurements of electrochemical impedance spectroscopy and cyclic voltammetry was prepared by a simple method. The high catalytic activity makes it be a low-cost alternative counter electrode to platinum (Pt) to be used in quantum dots-sensitized solar cells (QDSSCs) based on polysulfide electrolyte. The photovoltaic performance enhancement of the quantum dots (QDs)-sensitized semiconductor thin films due to the PbS counter electrode was evaluated by fabricating QDSSCs based on CdSe QDs-sensitized ZnO (SnO2) thin film. CdSe QDs-sensitized ZnO thin film has the lower internal total series resistance and electron transmission time, the higher electron lifetime and electron collection efficiency than the CdSe QDs-sensitized SnO2 thin film. Replacing the Pt counter electrode with the PbS counter electrode leads to more improvement on the short circuit photocurrent density for QDSSC based on the ZnO thin film than the SnO2 thin film. Therefore, the process to limit the photovoltaic performance of CdSe QDs-sensitized solar cell and the possible way to improve the photovoltaic performance were analyzed.

Photoactive p-type PbS as a counter electrode for quantum dot-sensitized solar cells

A photoactive PbS film synthesized by successive cycles of coating with ionic solutions and reaction can function as a performance-promoting counter electrode for quantum dot-sensitized solar cells (QDSSCs). The PbS film has a wide absorption spectrum that extends to the near infra-red region, making it capable of absorbing the long-wavelength light that penetrates the photoanode of a QDSSC. Under simulated one-sun illumination, this PbS film exhibits a p-type photovoltaic response in a polysulfide electrolyte, showing a quasi-Fermi level shift of +0.25 V. For QDSSCs consisting of a TiO2/CuInS2/CdS/ZnS photoanode and a polysulfide electrolyte, the PbS film outperforms Pt and CuS films as a counter electrode even though CuS has a much higher electrocatalytic activity in the polysulfide electrolyte than PbS. The photoactive characteristics of the PbS electrode increase the photocurrent of the resulting QDSSC. The p-type conductivity of the PbS forms a partial tandem junction between the PbS and the anode, increasing the photovoltage and the fill factor. Under one-sun illumination, a QDSSC assembled with the photoactive p-type PbS counter electrode achieves a maximum power conversion efficiency of 4.7%, which is more than 15% greater than that of a cell assembled with the highly electrocatalytically active CuS.

Electrochemical Aspects of the Nitric Acid Leaching of Lead Sulfide Concentrates: on the Way to a Highly Effective Method for Pb Recovery

Examination of the kinetics of hot nitric acid based leaching of a lead sulfide concentrate together with changes of potential of immersed Pt or PbS electrodes has revealed three stages of the leaching. The acidic decomposition of minerals that produces aqueous sulfide that is then oxidized by nitrate plays a major role in the first, slow leach stage. In the second stage, PbS oxidation is effectively accelerated by accumulated Fe3+/Fe2+ ions, yielding largely elemental sulfur and making the process electrochemical in nature. The formation of predominant sulfate and the process impeding in the third stage seem to be due to oxidative action of nitrogenous species. It is proposed that leaching in practice is performed using cold ferric nitrate solution as this was found to be a surprisingly effective and selective oxidant for PbS. A process flowsheet for the treatment of the Gorevsky flotation lead concentrate was developed.

The influence of silver ion on the electrochemical response of chalcopyrite and other mineral sulfide electrodes in sulfuric acid

The electrochemical behavior of chalcopyrite electrodes in H 2SO 4 solutions with and without silver ion has been investigated and has provided additional information concerning the enhanced or catalyzed leaching rates previously observed for the ferric sulfate leaching of CuFeS 2 in the presence of Ag +. A careful analysis of the cyclic voltammetry for CuFeS 2 electrodes in the presence of silver ion, indicates the formation of Ag 2S and metallic silver on the chalcopyrite surface, and that cyclic voltammetry for CuFeS 2 in solutions containing Ag + is an integration of the electrochemical responses for CuFeS 2 and Ag 2S. Consistent with previously reported leaching responses, additions of Ag + up to an optimum of approximately 10 -3M result in higher anodic currents for CuFeS 2 electrodes Concentrations of 10 -3M and larger cause a decrease in current which is attributed to the precipitation of Ag 2SO 4. The effect of Ag + on the individual anodic and cathodic half cell reactions has also been examined by means of a dual cell apparatus and has shown that added silver affects the anodic dissolution reaction and has no effect on the cathodic half cell, i.e. the Fe 2+/Fe 3+ couple. These results along with mass balances performed at constant anodic potential are considered in the context of reactions between CuFeS 2 and added silver which are indicated. The apparent catalysis is believed to occur through a change in morphology or conductivity of the normally protective sulfur layer which forms on CuFeS 2 through reactions involving Ag 2S or elemental silver. A preliminary exploration of other systems in which catalysis or enhancement may be found has also been briefly investigated using ZnS and PbS electrodes.

Photoelectrochemical cells with mixed polycrystalline n-type CdSPbS and CdSCdSe electrodes

The photoelectrochemical behaviour of n-type CdS (polycrystalline) containing small amount of PbS or CdSe in S 2− /S 2− n redox system has been studied. Mixed polycrystalline n-type CdSPbS electrodes were prepared by electrodeposition and the n-type CdSCdSe electrodes were made by partial replacement of sulphide ions of CdS electrode with selenide ions from a solution of sodium selenosulphate. It has been observed that both the mixed chalcogenide electrodes exhibit better photoresponse than the simple CdS electrode.

Preparation of a void-free PbS electrode and the influence of oxygen on its anodic behaviour

Attempts were made to overcome the difficulties encountered in fusing and casting a void-free PbS electrode that can withstand the effects of electrolysis. Experiments using a BN mould proved very successful in the preparation of a void-free electrode. The anodic behaviour of a PbS electrode prepared in this way was studied in a hydrochloric acid medium at 25 °C in the absence and presence of oxygen.