可視光照射下でH2O2を生成するp型銅系硫化物光電カソード電極の開発に関する研究

九州工業大学博士学位論文 学位記番号：工博甲第558号 学位授与年月日：令和4年9月26日Introduction|Visible light-driven H2O2 synthesis by a Cu3BiS3 photocathode via a photoelectrochemical indirect two-electron oxygen reduction reaction|Preparation of Cu3VS4 photocathode and its application in the preparation of H2O2 by oxygen reduction|Conclusion and outlook|Acknowledgements|List of Publications九州工業大学令和4年

Copper–antimony and copper–bismuth chalcogenides—Research opportunities and review for solar photovoltaics

The ternary Cu-Sb- and Cu-Bi-chalcogenides present a rich range of compounds of potential use for large-scale photovoltaics from Earth abundant elements. This paper reviews the state of fundamental knowledge about them, and their technological status with regard to solar cells. Research targets and missing data are highlighted, which may provide opportunities to help realize the goal of sustainable photovoltaics. The family of ternary Cu-Sb- and Cu-Bi-chalcogenides and their solid solutions present a rich selection of potential candidates for Earth-abundant low toxicity photovoltaic (PV) absorber materials. Moreover, they have some novel features imparted by the ns2 lone pair of electrons on the Sb and Bi ions. This review evaluates them as electronic materials, including experimental and theoretical evaluations of their phases, thermodynamic stability, point defects, conductivity, optical data, and PV performances. Formation of the materials in bulk, thin film, and nanoforms and the properties of the materials are critically assessed with relevance to their suitability for PV devices. There is special emphasis on CuSbS2 and CuSbSe2 which form the mainstay of the device literature and provide the most insights into the present-day limitation of the device efficiencies to 3 or 4%. Missing features of the literature are highlighted and clear statements recommending potential research pathways are made, which may help advance the technological performance from its present stuck position

Study of heterostructures of Cu3BiS3–buffer layer measured by Kelvin probe force microscopy measurements (KPFM)

The interface formed between Cu3BiS3 thin films and the buffer layer is a potentially limiting factor to the performance of solar cells based on Al/Cu3BiS3/buffer heterojunctions. The buffer layers of ZnS and In2S3 were grown by coevaporation, and tested as an alternative to the traditional CdS deposited by chemical bath deposition. From the Kelvin probe force microscopy measurements, we found the values of the work function of ZnS, In2S3, and CdS, layers deposited into Cu3BiS3. Additionally, different electronic activity was found for different grain boundaries (GBs), from studies under illumination, we also found the net doping concentration and the density of charged GB states for Cu3BiS3 and Cu3BiS3/CdS

2023 roadmap on photocatalytic water splitting

As a consequence of the issues resulting from global climate change many nations are starting to transition to being low or net zero carbon economies. To achieve this objective practical alternative fuels are urgently required and hydrogen gas is deemed one of the most desirable substitute fuels to traditional hydrocarbons. A significant challenge, however, is obtaining hydrogen from sources with low or zero carbon footprint i.e. so called ‘green’ hydrogen. Consequently, there are a number of strands of research into processes that are practical techniques for the production of this ‘green’ hydrogen. Over the past five decades there has been a significant body of research into photocatalytic (PC)/photoelectrocatalytic processes for hydrogen production through water splitting or water reduction. There have, however been significant issues faced in terms of the practical capability of this promising technology to produce hydrogen at scale. This road map article explores a range of issues related to both PC and photoelectrocatalytic hydrogen generation ranging from basic processes, materials science through to reactor engineering and applications for biomass reforming

SEARCH FOR NATURALLY OCCURRING SUPERCONDUCTIVITY AND NOVEL PHENOMENA: MAGNETIC TRANSITIONS IN NATURAL TRANSITION METAL COMPOUNDS

Transition metal chalcogenides and transition metal arsenides are important families of natural mineral compounds widely distributed in the natural world. With similar structural and electronic properties of transition metal oxides, natural transition metal compounds are expected to have similar novel phenomena. With an ongoing project for searching natural superconductors in collaboration with Department of Mineral Science, Smithsonian National Museum of Natural History, we had a chance to investigate several natural minerals from the Smithsonian Museum in order to study previously unexpected naturally occurring mineral compounds for interesting ground states. We found several interesting magnetic transitions in these natural occurring mineral samples. Some of the magnetic transitions are not reported, some of the transitions are associated with other unreported novel quantum phenomena. In this thesis, I will discuss Bornite (Cu5FeS4), Berthierite (FeSb2S4), Nagyagite (Pb5Au(Te,Sb)4S58), Maucherite (Ni11As8) and related experiments in detail. Bornite (Cu5FeS4) has a semiconductor-insulator transition accompanied with an antiferromagnetic transition. As shown by our ability to tune the transition temperature and low-temperature metallicity by applying external pressure, Bornite may be a good candidate for Mott system and searching new superconductors. Berthierite (FeSb2S4) is a quasi-1-dimensional antiferromagnet. With strong anisotropic physical properties, berthierite may provide a very good system for understanding the low dimensional magnetic material. A Ferromagnetic order was found in natural Nagyagite (Pb5Au(Te,Sb)4S58) samples. The magnetic order, the weak anti-localization property with strong spin-orbital coupling and the 2-dimensional structure of this compound makes it a very interesting system for realizing topological properties in a natural compound. The magnetic order and transitions in both natural and synthetic Maucherite (Ni11As8) samples show interesting finite-size scale effect. It gives us a different approach to understand the differences in some physical properties between natural and synthetic compounds. Also, we will present a summary of other magnetic transitions and magnetic properties of more than 40 distinct minerals for this study and show the relation and similarities between strongly correlated transition metal oxide materials and other quantum materials. We will also make a list of other transition metal minerals that are worthy of investigation based on our research experience

Beyond methylammonium lead iodide: prospects for the emergent field of ns(2) containing solar absorbers

The field of photovoltaics is undergoing a surge of interest following the recent discovery of the lead hybrid perovskites as a remarkably efficient class of solar absorber. Of these, methylammonium lead iodide (MAPI) has garnered significant attention due to its record breaking efficiencies, however, there are growing concerns surrounding its long-term stability. Many of the excellent properties seen in hybrid perovskites are thought to derive from the 6s(2) electronic configuration of lead, a configuration seen in a range of post-transition metal compounds. In this review we look beyond MAPI to other ns(2) solar absorbers, with the aim of identifying those materials likely to achieve high efficiencies. The ideal properties essential to produce highly efficient solar cells are discussed and used as a framework to assess the broad range of compounds this field encompasses. Bringing together the lessons learned from this wide-ranging collection of materials will be essential as attention turns toward producing the next generation of solar absorbers

Electronic Characterisation of Earth-Abundant Sulphides for Solar Photovoltaics

This thesis explores the electronic characterisation of materials for use as absorber layers within photovoltaic solar cells: an attractive solution to the energy crisis. Primarily, XPS was used to characterise CuSbS₂, Cu₃BiS₃, SnS, and Cu₂ZnSnS₄. All of these materials can be classified as earth-abundant: an important factor when considering materials that are both readily available and environmentally friendly. To varying degrees, all of these materials are established as potential absorber layers, with reports of successful, albeit low-efficiency devices. Also, the literature is often scant with regards to more fundamental characterisation of these materials, specifically in terms of how the underlying electronic structure affects properties that are pertinent to solar cells. Where XPS is utilised, it often lacks rigour, and is obfuscated by the complexities of the spectra. Work is then presented with two aims. First, to use a combination of high-quality XPS measurements and density of states calculations, in order to give insight into the electronic structure of the materials. Second, to present the full potential of XPS, as applied to solar absorbers, and how this technique complements others that are used for characterisation. Without exception, each material demonstrated natural band positions that make them unsuitable for use with established solar cell technologies. That is, a low IP (4.71–5.28 eV), resulting in a large CBO (0.5–0.85 eV) with CdS, for example. This offers some explanation to the poor efficiencies. These properties were found to be a consequence of the bonding nature of the valence and conduction bands, differing to the conventional absorber materials because of the influence of lone-pair electrons or other second-cation states. The power of XPS was demonstrated for application to absorber materials. The presence, effects, and formation pathways of contamination of the materials were elucidated using XPS, showing how the presence of such can act adversely to the performance of cells, especially with regards to oxidation, and also how these factors have been overlooked in the past. When coupled with other, complementary techniques, it has the ability to aid in the phase identification of a grown material, and also to help determine the presence of unwanted phases, which cause detriment to the device. For these applications, the methods, fitting procedures and analysis considerations detailed in this thesis should be followed. Research interest in these materials should be maintained based on the findings, with new approaches to cell design being aided by the characterisation methods developed here