bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Keynote) Photoelectrochemistry - Looking Back to the Future
Authors: Uosaki Kohei 
Published: February 2020

Photoelectrochemistry and/or semiconductor electrochemistry are of active research fields and thousands of papers in these fields are published annually. They attract many research groups because their potential importance in achieving low carbon society based on renewable energy, i.e., solar energy. Research on photoelectrochemistry was very active in late 1970's and 1980's after the 1st oil crisis following the suggestion by Fujishima and Honda that solar energy may be directly converted to a chemical energy, hydrogen, by using semiconductor/aqueous electrolyte solution/metal cells,1 although semiconductor electrochemistry was studied systematically since 1950's and many reviews and books were published by early 1970's.2-8 ECS organized symposia on photoelectrochemistry/semiconductor electrochemistry in the annual meetings and many proceeding volumes were published.9-14 Major target of the research changed from solar energy conversion to environmental issues and activity declined due to the lack of funding, particularly in the US. There must be reasons why photoelectrochemistry lost supports as solar energy conversion process in 1990's and it is a good time to look back what had been achieved, what were the problems, and are these problems solved.
In this talk, I will try to sum up the results achieved by 1990's and compare them with current activities.
References
1. A.Fujishima and K. Honda, Nature, 238 (1972) 37.
2. M. Green, in Modem Aspects of Electrochemistry, No. 2. Ed. by J. O’M. Bockris, Butterworths, London, 343-407 (1959).
3. J. F. Dewald. in Semiconductors. ACS Monograph, No. 140, Ed . by N. B. Hannay, Reinhold, New York, 727-752 (1959).
4. H. Gerischer. in Adv. Electrochem. Electrochem. Eng., Vol. 1, Ed . by P. Delahay, Interscience, New York, 139-232 (1961).
5. P. J. Holmes. Ed.. The Electrochemistry of Semiconductors, Academic. London, 1962.
6. V. A. Myamlin and Yu. V. Pleskov，Electrochemistry of Semiconductors. Plenum, New York. 1967.
7. H. Gerischer, in Physical Chemistry: An Advanced Treatise, Vol. IXA. Ed. by H. Eyring. Academic. New York. 1970, Chap. 5.
8. S. R. Morrison, Prog. Surf. Sci., 1(1971) 105.
9. PV 77-3 "Semiconductor Liquid-Junction Solar Cells", Ed. A. Heller.
10. PV 82-3 "Photoelectrochemistry: Fundamental Processes and Measurement Techniques", Ed. W. L. Wallace, A. J. Nojik, and S. K. Deb.
11. PV 88-14 "Photoelectrochemistry and Electrosynthesis on Semiconducting Materials", D. S. Ginley, A. Nojik, N. Armstrong, K. Honda, A. Fujishima, T. Sakata, and T. Kawai.
12. PV 93-18 Environmental Aspects of Electrochemistry and Photoelectrochemistry", M. Tomkiewicz, H. Yoneyama, R. Haynes, and Y. Hori.
13. PV 94-19 "Water Purification by Photocatalytic, Photoelectrochemical, and Electrochemical Processes", T. L. Rose, E. Rudd, O. Murphy, and B. E. Conway.
14. PV 97-20 "Photoelectrochemistry", .K. Rajeshwar, L. M. Peter, A. Fujishima, D. Meissner, and M. Tomkiewicz.
(Invited) Transient Absorption Spectroscopy of Au/CeO2 Powder
Authors: Ziani Ahmed , Nadeem Amtiaz , Idriss Hicham 
Published: February 2020

CeO2 is one of the most studied metal oxide catalysts due to its redox and oxygen transport properties. Transitions occur between the O2p - Ce5d (ca. 6 eV) and the O2p - Ce4f (ca. 3.5 eV) in addition to defect states that can be present between the O2p and Ce4f levels [1],[2]. Very few studies have been conducted by transient absorption spectroscopy (TAS) to probe into the generated charge carrier dynamics[3],[4] to date. The system Au (nanoparticles) / CeO2 has been studied extensively in catalysis because of many reactions such as CO oxidation and ethanol reforming [5],[6]. Because of the plasmonic nature of Au nanoparticles, the interface Au/CeO2 and consequently the charge carriers lifetime and concentration are poised to be affected. In this work, we have studied by pump-probe TAS the lifetime of excited electrons for a series of Au/CeO2 particles (1-4 Au wt. %). Upon excitation with a 480 nm light (2.55 eV), TAS signal in the 700-900 nm range (1.75-1.35 eV) was observed for both CeO2 alone and Au/CeO2. This signal is tentatively attributed to defects states between Ce4f and O2p. Excitation with a 300nm light (4.2 eV) resulted in the appearance of a strong signal in the 400-500 nm (3.1-2.5) in addition to the 700-900 nm. The 3.1-2.5 eV signal might be originating from the Ce4f-O2p recombination process. The presence of gold nanoparticle was found to increase the lifetime of this signal, and this might be linked to an electric field effect. Work in progress in order to extract kinetic information related to the charge lifetime in both regions and further probe into gold plasmon-CeO2 effects.
[1] El Khalifi, M.; Picaud, F.; Bizia, M.; Anal. Methods, 2016, 8, 5045–5052.
[2] Castletona, C.W.M.; Kullgren, J.; Hermansson, K.; J. Chem. Phys., 2007, 127, 244704, 1-11.
[3] Singh, P.; Srivatsa, K.M.K.; Jewariya, M.; Optical Mater., 2016, 58, 1-4.
[4] Pettinger, N. W.; Williams, R.E.A.; Chen, J.; Kohler, B.; Phys. Chem. Chem. Phys., 2017, 19, 3523-3531.
[5] Zhang, S.; Li, X.-S.;Chen, B., Zhu, X.; Shi, C.; Ai-Min Zhu, A.-M.; ACS Catal., 2014, 4, 3481–3489.
[6] Sheng, P.-Y.; Bowmaker, G.A.; Idriss, H.; Appl. Catal. A, 2004, 261, 171-181.
(Invited) Hafnium Oxynitride-Derived Electrocatalyst with High Activity and Stability in Strong Acid for Both Hydrogen Evolution and Oxidation Reactions
Authors: Koel Bruce E. 
Published: February 2020

There is a need to decrease our dependence on fossil fuels for producing energy and chemicals, and there is a great interest in using sunlight to drive fuel-forming reactions to produce solar fuels. Solar fuels are important future energy carriers and provide a way to store solar energy, and this makes for a theme that is continuing to move up the global research agenda. Alternatively, with solar and wind power creating increasingly large amounts of electricity, an important question is how can we take advantage of the expanding increase of renewable electricity for catalysis? By applying a voltage in electrocatalysis, we can harness the flow of electrons to form and break chemical bonds, with the remaining challenge to carry out this catalysis with high selectivity and energy efficiency utilizing sustainable electrocatalyst materials.
Renewable H2 technologies could provide alternatives to fossil fuels, and this could be enabled by H2 production from water electrolysis and generation of electricity using H2 fuel cells. However, lack of highly active, stable, earth-abundant electrocatalysts for carrying out the hydrogen evolution reaction (HER) in water electrolyzers and the hydrogen oxidation reaction (HOR) in fuel cells, is a major technical challenge for developing economical polymer electrolyte membrane (PEM)-based electrolyzers and fuel cells. Carrying out these reactions in strongly acidic conditions is desirable because of the advantages of using proton exchange membranes, including compact system design, lack of liquid electrolyte, high current density and energy efficiency, and high gas purity. Recently, we have found a material that demonstrates excellent HER and HOR activities in acids using non-platinum group metal (PGM) catalysts [1]. Processing hafnium oxide with an atmospheric nitrogen plasma forms an acid-insoluble hafnium oxynitride material. We propose that under electrochemical environments this material is transformed into an active oxynitride hydroxide that demonstrates unprecedented high catalytic activity and stability for both HER and HOR in strong acidic media for earth-abundant materials. The zero onset potentials and high current densities demonstrate that this material is a promising alternative to Pt. This opens up new opportunities to develop technologically and economically viable PEM-fuel cells, regenerative fuel cells, and electrolyzers. Furthermore, these results have broad implications for using nitrogen incorporation (e.g. by nitrogen plasma treatment) to activate other non-conductive compounds and films to form new active electrocatalysts.
1. X. Yang, F. Zhao, R.S. Selinsky, Z. Chen, Y.-W. Yeh, N. Yao, C.G. Tully, and B.E. Koel, Nature Communications, 10, 1543−1−8 (2019).
(Invited) Energetic Hole Ejection Involved in Plasmon-Induced Charge Separation: Local Oxidation and an Application to Near IR Photovoltaics
Authors: Tatsuma Tetsu , Nishi Hiroyasu , Ogata Rui , Lee Seung Hyuk 
Published: February 2020

Plasmon-induced charge separation (PICS)1-3 involves electron transfer from plasmonic nanoparticles of Au, Ag, or Cu to a semiconductor such as TiO2.1-4 PICS of Ag-TiO2 systems often involve oxidation of Ag to Ag+,5 and that this reaction occurs preferentially at resonance sites, at which optical near fields are localized.6-8 This cannot be ascribed to thermal acceleration of reaction,9 but can be explained in terms of ejection of energetic holes from the nanoparticles as Ag+ ions.
This hole ejection has been investigated further for Au nanocubes on TiO2 by using other reactions; Pb2+ oxidation to PbO2 and pyrrole oxidation to polypyrrole. Au nanocubes on TiO2 show distal mode, in which electron oscillation is localized at the top face of the nanocube, and proximal mode, in which electron oscillation is localized at the bottom face. In the case of Pb2+ oxidation, PICS for the distal mode and proximal mode resulted in PbO2 deposition at around the top face and the bottom face, respectively.10 However, in the case of pyrrole oxidation, both of the distal mode PICS and proximal mode PICS resulted in polypyrrole deposition at the whole surface of the nanocube.
On the basis of those results, we conclude that the localized oxidation and the delocalized oxidation are ascribed to energetic hole ejection mechanism and positive charge accumulation mechanism, respectively. We have applied energetic hole ejection to fabrication of chiral plasmonic nanostructures11 and near IR photovoltaics.12

Y. Tian and T. Tatsuma, J. Am. Chem. Soc., 127, 7632 (2005).

Y. Tian and T. Tatsuma, Chem. Commun., 2004, 1810.

T. Tatsuma, H. Nishi, and T. Ishida, Chem. Sci., 8, 3325 (2017) [review].

E. Kazuma and T. Tatsuma, Adv. Mater. Interfaces, 1, 1400066 (2014).

Y. Ohko, T. Tatsuma, T. Fujii, K. Naoi, C. Niwa, Y. Kubota, and A. Fujishima, Nat. Mater.,
2, 29 (2003).

E. Kazuma, N. Sakai, and T. Tatsuma, Chem. Commun., 47, 5777 (2011).

I. Tanabe and T. Tatsuma, Nano Lett., 12, 5418 (2012).

K. Saito, I. Tanabe, and T. Tatsuma, J. Phys. Chem. Lett., 7, 4363 (2016).

K. Saito, K. Setoura, S. Ito, H. Miyasaka, Y. Mitsuda, and T. Tatsuma, ACS Appl. Mater. Interfaces, 9, 11064 (2017).

H. Nishi, M. Sakamoto, and T. Tatsuma, Chem. Commun., 54, 11741 (2018).

K. Saito and T. Tatsuma, Nano Lett., 18, 3209 (2018).

S. H. Lee, H. Nishi, and T. Tatsuma, Nanoscale, 10, 2841 (2018).
(Invited) Ultrafast X-Ray Studies of Interfacial Energy- and Charge-Transfer Dynamics
Authors: Gessner Oliver 
Published: February 2020

The success of many emerging molecular electronics concepts hinges on an atomistic understanding of the underlying electronic dynamics. Processes evolving on spatial and temporal scales spanning orders of magnitude have to be connected in order to gain a comprehensive understanding of the fundamental dynamics and scaling laws that enable molecular, interfacial, and macroscopic charge and energy transport. Time-domain X-ray spectroscopy techniques have the potential to provide a deeper understanding of electronic dynamics in complex, heterogeneous systems owing to their elemental site specificity and sensitivity to local valence electron configurations.
We present femtosecond to picosecond time-resolved X-ray photoelectron spectroscopy (TRXPS) studies of photoinduced charge transfer dynamics in nanoporous films of N3 dye-sensitized ZnO and bilayer heterojunctions consisting of copper phthalocyanine (CuPc) electron donors and C60 acceptors. For the N3/ZnO system, differential TRXPS line shifts provide site-specific access to the locations of intermittently trapped electrons, interfacial dipoles, as well as charge delocalization and recombination dynamics. For the CuPc/C60 heterojunction, a deeper understanding of the predominant energy transport and charge generation mechanisms is achieved. Contrary to common belief, fast intersystem crossing from initially excited singlet excitons to triplet excitons within the bulk of the donor domain is not a loss channel but the triplet excitons contribute to a significantly larger extent to the time-integrated interfacial charge generation than the initially excited interfacial singlet excitons. The TRXPS data provide direct access to the diffusivity of the triplet excitons in the CuPc donor domain DCuPc = (1.8 ±1.2) × 10−5 cm2/s and their diffusion length Ldiff = (8 ± 3) nm.
Preliminary TRXPS results will be presented for a model system for plasmon-enabled photocatalytic nano-assemblies consisting of a nanoporous TiO2 layer sensitized with gold nanoparticles (Au NPs). Clear differences between the temporal responses of the Au4f and Ti2p photolines are observed, indicating both the interfacial site-specificity of photoinduced electronic dynamics and the capacity of TRXPS to distinguish them.

Figure 1
Photoelectrochemical and Surface Analysis of CdSe-Poma Composites on Highly Oriented Pyrolytic Graphite
Authors: Casto Sophia Maria , Dulovic Stephanie , Widera Justyna , Maranowski Bartosz , Strawski Marcin , Szklarczyk Marek 
Published: February 2020

Abstract

Over the past decade, semiconductors have been of great interest and are currently found in numerous devices such as: computers, cell phones, and medical equipment. Semiconductors are the integral component of solar cells, converting solar energy into electricity.
This research studies the photoactivity and stability of semiconductors cadmium selenide (CdSe) and poly(o-methoxyaniline) (POMA) deposited on highly oriented pyrrolic graphite (HOPG). The CdSe-POMA deposits were electrochemically deposited on HOPG using cyclic voltammetry. The composites were deposited in the following order: (1) CdSe before POMA (CdSe/POMA), (2) POMA before CdSe (POMA/CdSe), and (3) CdSe and POMA simultaneously (CdSe+POMA). For the sequential depositions, the deposition of CdSe and POMA were performed sequentially so that the surface consisted of the desired hybrid. The CdSe layer was deposited for 20 cycles from a solution of 5 mM CdSO4 and 1 mM SeO2 in 0.1 M HClO4. The polymerization of POMA was accomplished by electrochemical cycling for 5 cycles from a 0.06 M o-anisidine solution in 0.1 M HClO4. The deposition of CdSe+POMA was performed by electrochemical cycling for 20 cycles in a solution of 5 mM CdSO4, 1 mM SeO2, and 0.06 M o-anisidine in 0.1 M HClO4.
The photoactivity and stability of the deposits were studied using open circuit potentiometry (OCP), cyclic voltammetry (CV), and chronoamperometry (i/t) in 0.1 M Na2SO3. The CdSe/POMA deposit had the greatest photopotential at around 200 mV while POMA/CdSe and CdSe+POMA presented lower photopotentials at 30 mV and 14 mV respectively. Chronoamperometric studies found that CdSe/POMA had the greatest photocurrent density of 17 µA/cm2 compared to 0.05 µA/cm2 for POMA/CdSe and 0.42 µA/cm2 for CdSe+POMA. Photoelectrochemical measurements suggest that POMA/CdSe and CdSe+POMA deposits were less stable than CdSe/POMA. X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM) were used to analyze the surface. The surface morphology and chemical composition of the deposits were studied before and after photo-studies to observe the degree of degradation after the sample was exposed to light. Measurements found that the POMA/CdSe and CdSe+POMA deposits degraded more than CdSe/POMA, suggesting that depositing the polymer over the CdSe film might be necessary in reducing the degree of degradation when the sample is exposed to light.
PVDF/SiO2-TiO2 Photocatalytic Membranes for Water Treatment
Authors: Zhang Xinrong 
Published: February 2020

Polymeric membranes have been widely used for many kinds of wastewater treatment. However, the fouling of membranes decreases their permeability. TiO2 is widely used for water treatment because its photocatalytic properties, stability, availability and desirable hydrophilicity properties. In the recent years, many researchers have investigated the possibility of coupling polymeric membrane filtration technology and TiO2 photocatalysis to improve membrane performance by reducing fouling and increasing hydrophilicity. Because TiO2 particles on the membrane surface not only increase membrane hydrophilicity, but also create a photocatalytic property, formation of cake layer and blocking of membrane pores are prevented. So, the polymeric membranes with TiO2-based photocatalysts provide an opportunity for wastewater treatment.
In previous studies, our group revealed that PVDF/TiO2 hybrid hollow fiber membrane through a phase inversion method to improve filtration efficiencies and antifouling properties.
In the present work, SiO2 as inorganic material into PVDF membrane matrix increases the membrane permeability. SiO2 modified PVDF/TiO2 hybrid hollow fiber membrane is prepared by similar strategy. The membranes performances are evaluated based on the water permeability, humic acid (HA) rejection and antifouling properties. And this work focuses on the long-term stability and antifouling performance, especially under visible light.
(Invited) Aqueous Thermal-Electrochemical Catalysis for Light Alkane Upgrading
Authors: Kronawitter Coleman X 
Published: February 2020

The recent dramatic increase in supply of natural gas in the United States, largely enabled by rises in shale gas production, presents a unique opportunity to develop new catalytic processes that utilize abundant light alkanes for chemical manufacturing and transportation fuel synthesis. Alkenes as well as alcohols and other oxygenates are attractive target product molecules because they are either commodity chemicals or serve as precursors for production of commodity synthetic materials. This presentation will describe several approaches for designing new catalysts and reaction schemes for light alkane upgrading. These approaches include thermal catalytic, electrocatalytic, and hybrid thermal-electrocatalytic reactions in both batch and flow conditions.
The presented work shows that oxidative functionalization of C-H bonds is possible using only air, water, and electricity as inputs when suitable catalysts and reaction conditions are utilized. Results demonstrate conversion of methane and ethane into a number of oxygenates and hydrocarbons at temperatures below 60 ºC in aqueous conditions, and quantify the associated catalytic performance. These efforts are supplemented by ex situ materials characterization and operando FTIR spectroscopy measurements, which provide new insights into the nature of these aqueous thermal and thermal-electrocatalytic reactions. The use of reactive oxidizing species generated from air and water for low temperature hydrocarbon catalysis has enormous potential to open new avenues of research. Additionally, the fundamental insights gained on the role of water in driving product selectivity in these reactions will be of interest to the broader catalysis community, which often encounter water in the gas phase as a side reactant.
Strongly Coupled Ni-Molybdenum Carbide Grafted N-Doped Carbon Architectures for Efficient Electrocatalysis
Authors: Das Debanjan 
Published: February 2020

Despite the recent promise of transition metal carbides as non-precious catalysts for hydrogen evolution reaction (HER), their extension to oxygen evolution reaction (OER) in order to achieve the goal of overall water splitting remains a significant challenge. Herein, a new Ni/MoxC (MoC, Mo2C) nanoparticles supported N-doped graphene/CNT hybrid (NC) catalyst is developed via a facile, one-step integrated strategy which can catalyze both the HER and OER in an efficient and robust manner. The catalyst affords low overpotentials of 162 and 328 mV to achieve a current density of 10 mA/cm2 for HER and OER, respectively, in an alkaline medium which either compares favourably or exceeds most of the Mo-based catalysts documented in the literature. The electronic synergistic effect between MoxC, Ni and NC are responsible for the higher electrocatalytic activity wherein, a tandem electron transfer process yields both excellent HER and OER activity. [1] Unfortunately, however, the synergy among the components was curtailed on account of large spatial separation. To mitigate this problem, we pyrolyzed a PANI/NiMoO4 nanowire@rGO hybrid which brought the individual components closer as compared to the previously adopted method resulting in improved catalytic activity. To further enhance the intimacy in these multi-component catalysts, a MOF-confined synthesis method was developed which resulted in the best activity among all the catalysts developed in the series. Moreover, we further extended this strategy to other MOFs resulting in Co/Mo2C/NC architecture which points to the versatility of this method.
[1] D.Das, S.Santra and K.K Nanda, ACS Appl. Mater. Interfaces, 2018, 10, 35025−35038
High Efficiency PEM Water Electrolysis Enabled By Advanced Catalysts, Membranes and Processes
Authors: Capuano Christopher B , Ayers Kathy , Manco Judith , Wiles Luke , Zenyuk Iryna V. , Leonard Emily , Kusoglu Ahmet , Weber Adam Z. , Danilovic Nemanja , Alia Shaun M , Ulsh Michael , Mauger Scott A , Pfeilsticker Jason , More Karren L. 
Published: February 2020

Commercial water electrolysis technologies, including proton exchange membrane electrolysis (PEMWE), are the only renewable hydrogen generation technologies that can achieve the U.S. Department of Energy (DOE) cost targets within the next ten years at the required scale, based on the supply chain maturity and materials performance. In particular, membrane and electrode modifications have enabled the use of advanced electrolysis membranes to achieve the efficiency targets, while nanoengineered alloy catalyst layers (CLs) have been pursued to meet the cost and efficiency targets. These advancements have been achieved by building the basic understanding to allow the successful technical development and include: (1) Mechanical and chemical understanding of membranes in liquid water below 90oC; (2) Characterization of as-deposited electrodes and MEAs after operation; (3) Water management in the anode catalyst layer, dependence on catalyst loading and porous transport layer form factor; and (4) Long-term degradation rate and stability of engineered alloy Ru-Ir alloy nanocatalysts in well-defined anode catalyst layers.
Nel Hydrogen’s pathway to meet these DOE goals is through the i) use of 50-75% thinner membranes that operate at 80-90 oC, while controlling mechanical creep and gas crossover; ii) reducing the catalyst loading to 1/10th the current value on both electrodes, while controlling water distribution and the porous transport layer/catalyst layer (PTL/CL) electrochemical interface; iii) incorporation of a less stable but more active Ru containing catalyst managed on the anode side of the cell, which is achievable with lower voltage operation (accomplished via low ohmic drop in the anode catalyst layer, thinner membranes, and higher temperature operation); and iv) fabricating a membrane electrode assembly (MEA) integrating all of these characteristics.
In this talk, some of the advancements achieved and how these have impacted the cost of hydrogen will be discussed, as well as the longer-term targets that need to be reached to provide the robustness required for commercial applications. Additionally, cost models will be compared along with sensitivity analysis to show how the impact of operating parameters, with regard to the capital and operational expense for the PEM electrolysis technology cost, show the critical areas to focus on to provide the largest impact towards meeting cost target goals and what is required to go beyond.

Figure 1