bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Modification of Rutile TiO2 with Metal Chalcogenides for Hydrogen Evolution
Authors: Nolan Michael , Niemitz Lorenzo , Rhatigan Stephen 
Published: May 2020

The hydrogen evolution reaction (HER) is a key reaction in water splitting and there is an intensive search for suitable HER catalysts that will promote this reaction and also show good stability, while not using precious metals. We have studied the surface modification of rutile TiO2 with metal chalcogenide nanoclusters for the promotion of the hydrogen evolution reaction (HER) using density functional theory corrected for on-site Coulomb interactions (DFT+U).
Recently, metal chalcogenides have emerged as potential catalysts for the HER due to the favourable interaction of H at chalcogen sites, particularly those that are undercoordinated. In developing materials for HER the key descriptor has been the adsorption energy of hydrogen at the catalysts, with the target free energy being close to 0 eV. Analogous to noble metal loading, surface modification of TiO2 with nanoclusters of potential HER co-catalysts, based on earth-abundant materials, is an emerging strategy. This approach combines the desirable properties of a stable titania photocatalyst with active sites provided by the low-coordinated chalcogen ions of the supported clusters.
Our models consist of M4X4 (M = Sn, Zn; X = S, Se) nanoclusters at the rutile (110) surface and we examine the Gibb’s free energy of H adsorption at the modified surface which is a useful material descriptor in assessing the performance of a HER catalyst. These calculations take into account changes in the entropy and the zero-point energies (ZPEs) of the reactants and products, which our results show are material specific. As expected, the interaction of H is more favourable at the titania surface and forms stable hydroxyls. However, after subsequent adsorption events the surface sites become saturated and H adsorption at chalcogen sites exhibit Gibb’s free energies in the active range, particularly for MS modifiers relative to MSe.
Ir Decorated Fractal Ni Catalysts for the Oxygen Evolution Reaction
Authors: Hao Minghui , Gaudet Julie , Guay Daniel 
Published: May 2020

Porous and fractal Ni electrode synthesized by the Dynamic Hydrogen Bubbling Template (DHBT) method (Ni DHBT electrode) have shown very promising performances for the oxygen evolution reaction (OER) in alkaline electrolyte. This was thought to arise as a result of the extended electrochemical active surface area and its superaerophilic properties that facilitates the release of oxygen bubbles[1]. Herein, we report on a method to decorate the Ni DHBT electrode with Ir atoms via a galvanic replacement (GR) reaction. The resulting electrode has very low loadings of Ir (0.26 atom % as determined by EDX). As shown in Figure 1, micrometer-sized pores are observed at the surface of deposits, with pore walls exhibiting a highly porous cauliflower-like secondary structure, with much smaller pore diameter (typically less than 500 nm). The structure seen in Figure 1 was observed over the entire 0.32 cm2 geometric surface area of the deposits. The morphology of the Ir-modified electrode is not changed with respect to Ni DHBT electrode, indicating that the GR reaction is occurring only at the surface of the deposit. Voltammetry cyclic tests in 1M KOH solution showed hydrogen adsorption/desorption (Hupd) peaks of Ir as well as the redox peaks of Ni(OH)2 which suggested the coexistence of Ir and Ni content at electrode/electrolyte interface. The activity for the OER of Ni DHBT electrode was further improved by decoration with Ir, resulting in an overpotential of 195mV at 10 mA/cm2 and a Tafel slope of 46 mV/dec. To the best of our acknowledgment, this is one of the best performing Ni based OER catalysts reported so far. The interaction of oxygen bubbles with the electrode surface will also be assessed using both optical imaging and acoustic emission characterization.
[1] M. Hao et al., “Hydrogen Bubble Templating of Fractal Ni Catalysts for Water Oxidation in Alkaline Media,” ACS Appl. Energy Mater., vol. 2, no. 8, pp. 5734–5743, Aug. 2019.

Figure 1
Towards Selective Partial Water Oxidation to Form H2O2: An Attractive Substitute for O2 Evolution in Water Splitting
Authors: Mei Bastian Timo , Wenderich Kasper , Nieuweweme Birgit , Mul Guido 
Published: May 2020

Efficient and financially attractive (photo)electrochemical water splitting for the production of hydrogen (H2) is essential to drive a green hydrogen economy. However, techno-economic analysis predicts that the price of H2 obtained through (P)EC water splitting is over $10 000 ton-1 at solar-to-hydrogen (STH) efficiencies of ca. 10 %, whereas the current market value of H2 produced by conventional steam methane reforming is only $1400 ton-1.[1, 2] Co-production of high-value chemicals at the anode is an appealing strategy to increase the financial attractiveness of the production of 'green hydrogen.
In ‘classic’ (P)EC water splitting, oxygen is the main product at the anode, formed at a potential of E0 (O2/H2O) = +1.23 V vs RHE. Though thermodynamically less favorable (E0 (H2O2/H2O) = +1.78 V vs RHE), the selective partial oxidation of water to hydrogen peroxide (H2O2) is of industrial interest.[2] With a market price of $500-1200 ton-1 for H2O2 and given the low market value of O2 (only $35 ton-1), the financial incentive is clearly demonstrated. Considering that the demand for H2O2 is constantly increasing, hydrogen production through a process with concomitant H2O2 has a high potential of becoming competitive with steam methane reforming.
Here, we discuss the techno-economics of a PEC water splitting system producing H2O2 and H2. We will clearly show that an electrochemical process holds great financial promise for industrial development. Not only do we demonstrate at which prices H2 and H2O2 can be sold to make a profit, we also discuss which parameters need to be optimized to decrease the hydrogen price. Interestingly, when the H2O2 price is $0.85 kg-1, an STH of only 9.39% is required to compete with hydrogen production by steam methane reforming.
As the anodic formation of H2O2 is not yet well explored, it will also be shown that continuous electrochemically production of H2O2 at a rate of 0.092 µmol min-1 cm-2 @ 7.08 mA/cm2 through partial water oxidation can easily be achieved in an non-optimized electrochemical cell. Finally, the importance of electrolyte, electrode and reactor engineering to increase the Faradaic efficiency and the rate of H2O2 production will be revealed.

References

1. Shaner, M. R.; Atwater, H. A.; Lewis, N. S.; McFarland, E. W. A Comparative Technoeconomic Analysis of Renewable Hydrogen Production using Solar Energy. Energy Environ. Sci., 2016, 9, 2354-2371.
2. Mei, B.; Mul, G.; Seger, B. Beyond Water Splitting: Efficiencies of Photo-Electrochemical Devices Producing Hydrogen and Valuable Oxidation Products. Adv. Sustainable Syst. 2017, 1, 1600035.
The Controlled Preparation of Ordered Iridium Oxide Nanotubes Arrays for Oxygen Evolution Reaction
Authors: Lu Zhuoxin , Shi Yan , Wang Zhida , Guo Changqing , Tan Hongyi , Yan Changfeng 
Published: May 2020

Ordered electrode is believed to be the next generation of MEA. One-dimensional-arrays material possesses high surface area, oriented electron transfer pathway and facile mass transfer pathway, which shows great potential as electrocatalyst. For OER electrode, IrO2 is still the irreplacable choice at present status. To construct IrOx based nanotube/nanowire arrays could increase the performance of OER electrode with reduced loading amount of Iridium. Titanium oxide nanotube arrays (TNTA) is a promising candidate for the preparation of 1-D arrays electrode as its prominent stability, ordered structure and sufficient conductivity with simple modification. In order to achieve the open-end nanotube structure for the fully utilization of noble metal catalyst, controlled electrochemical deposition is applied.
In our previous work, IrOx nanotube arrays performs similar current density with 1/20 loading amount of commercial IrO2 nanoparticle at the same potential. To achieve the length control of IrOx nanotube arrays, the electrodeposition of IrOx on TNTA with cyclic voltametry method was studied. By altering the scan rate, continuous IrOx nanotube arrays with different length ranged from 500 nm to 1400 nm was achieved. This phenomenon may probably due to that the deposition in the tube is diffusion controlled, while the deposition at the mouth of TNTA keeps constant due to sufficient supplement of precursor form the bulk electrolyte. In a single cycle, as the depositing goes on, the concentration gradient along the tube forms and results in uneven deposition. Different scan rate results in different duration of depositing in a single cycle. And longer duration means more uneven deposition, and leads to shorter nanotube.
At present, to obtain IrOx nanotube arrays with uniform tube wall, control deposition with pulsed potential deposition method is studied. By altering the relaxation and deposition time, IrOx with uniform thickness and tunable length can be achieved. And the thickness of IrOx tube wall can be controlled, too. By achieving uniform and thinner tube wall, the utilization rate of Iridium can be further increased.
First Principles Modelling of Surface Modified TiO2 for Water Activation and Oxygen Evolution
Authors: Nolan Michael , Rhatigan Stephen 
Published: May 2020

The photocatalytic oxidation of water to molecular oxygen is a key step in the water splitting reaction. The development of robust catalysts with high efficiency in this half-reaction is crucial for achieving technological application of water splitting. Density Functional Theory simulations can provide key insights into potential catalysts for this reaction. In this contribution we describe our work on modelling of surface modified TiO2 focusing on water activation and the oxygen evolution mechanism on these heterostructures. Rutile and anatase TiO2 are modified with nanostructures of metal oxides, namely alkaline earth oxides, cerium oxide and manganese oxides; these are also being prepared and characterised at collaborators laboratories in the framework of an EU H2020 M-ERA.net 2 project RATOCAT.
We find that nanoclusters of these oxides with different compositions and adsorption modes are strongly adsorbed and can induce a red shift in light absorption towards the visible region of the electromagnetic spectrum. A simple model of the photoexcited state allows the localisation of electrons and holes produce by excitation to be determined and understood. Typically, DFT studies neglect key issues issues such as reducibility of the oxide or the role of adsorbed hydroxyls on the properties and the water activation processes in OER. We include a detailed analysis of reduction of the heterostructures, in which we find that loss of oxygen is generally favourable. In addition, the surface hydroxylation (through adsorption and dissociation of water) and the cluster hydroxylation are examined. We find that a single water molecule will dissociate at the supported oxide nanocluster, with large energy gain that indicates hydroxyl groups will be present and must be accounted for.
With a suitable model of a hydroxylated oxide heterostructure, including oxygen vacancies, we explore water activation and find for those structures with hydroxyls and single oxygen vacancies, the water adsorption is dissociative but with moderate energy gains. Too high an energy gain and the subsequent OER steps are not favourable. We determine the step with the highest free energy cost and use this to estimate an overpotential for these heterostructures as well as determining key aspects of these structures that drive favourable OER.
Support for this work from Science Foundation Ireland through the H2020 M-ERA.net 2 co-fund program, Grant Number 16/M-ERA/3418 is acknowledged. We also acknowledge access to computing resources through the SFI funded Irish Centre for High End Computing, ICHEC.
Oxygen Evolution Reaction/Oygen Reduction Reaction Properties of Massively Synthesized a NiMoS with Solvothermal Method
Authors: Choi Yusong , Ahn Tae-Young , Yu Heryeon , Kim Jiyoun , Cho Jang-hyeon 
Published: May 2020

The oxygen electrode is the most important component in lithium-air batteries for oxygen reduction and evolution reaction (OER/ORR) to get closer to the theoretical energy density of 11,238 Wh/kg, which is the best among the batteries ever developed. Many carbon materials have been researched as a candidate oxygen electrode for lithium-air batteries such as a carbon black, CNTs and graphene. Compared to the many research results, there are still many controversies on the optimum oxygen electrode for lithium-air batteries. Besides that, carbon and binder have been known to deteriorate OER/ORR properties for lithium-air batteries by generating Li2CO3 and other bi-product. Recently, HER and OER properties of heterogeneous MoS2/Ni3S2 have been reported for water splitting. The heterogeneous HER and OER performances of MoS2/Ni3S2 were better than the commercial HER and OER catalysts. Up till now, to my best knowledge, there's no report on ORR properties for homogeneous NiMoS. Therefore, to investigate the ORR properties of homogeneous NiMoS, the homogeneous NiMoS has been synthesized on Ni-foam as well as Ni-powder by various solvothermal methods such as applying to stir during solvothermal synthesis, increasing the pressure or applying the both. Finally, we successfully synthesized NiMoS massively with stirring at the pressure of 15 bar. Characterization for NiMOSs variously synthesized were conducted with SEM, TEM as well as OER/ORR properties using RRDE (Ring Rotating Disk Electrode).
As a result, homogeneous NiMoSs massively synthesized with stirring as well as high pressure of over 15 bar shows a unique homogeneous structure with sub-micron size. However, NiMoS synthesized under 2~3bar pressure with no stirring shows the tens of micron size as well as heterogeneous structure. Intriguingly, OER/ORR properties of massively synthesized NiMoS shows much better OER/ORR properties compared to the solvothermal synthesized NiMoS with no-stirring and at the pressure of 2~3 bar. These results show a very optimistic result for non-precious electrode material for the next generation Li-air battery as well as the fuel cell field.
Highly Active and Durable Transition Metal Oxide-Based Oxygen Electrode Catalysts for Unitized Reversible Fuel Cells
Authors: Choi Sung Ryul , Choi Sungyong , Kim Dongyeong , Park Jun-Young 
Published: May 2020

Facing with the increasing environmental concerns for global warming and environmental pollutions, it is essential to develop renewable and sustainable energy sources to substitute traditional fossil fuel-based technologies. As a major candidate technology, unitized reversible fuel cells (URFCs) are recognized as a promising electrochemical energy conversion device due to their high energy efficiency and negligible carbon emissions [1]. However, the low electrocatalytic activity related to the large overpotential loss for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the key technical issue for the development of URFCs [2]. Until now, precious metal-based catalysts (e.g., Pt/C, Ir/C, and IrO2) have been used for OER and ORR in URFCs due to high electrocatalytic activity [3]. Nevertheless, making commercialization of URFCs has hampered by the scarcity and limited durability of these materials [4, 5]. In order to solve these technical barriers, non-precious transition metal oxide based materials have considered as promising alternatives for bifunctional OER and ORR electrocatalysts because of their low cost, earth-abundance, and long-term stability [6]. However, transition metal-based oxygen catalysts have several issues such as low electrical conductivity, small surface area, and low electroactivity. Herein, as main strategies to improve bifunctional electrocatalytic activity for OER and ORR, other transition metals are doped to increase intrinsic property of oxide materials with hybridizing with highly conductive carbonaceous materials as supporting material. The synthesized catalysts are analyzed by various physicochemical and electrochemical analysis tools [7. 8].

References

1. Landon, E. Demeter, N. Inoglu, C. Keturakis, I. Wachs, R. Vasic, A. Frenkel, and J. Kitchin, ACS. Catal.
8, 1793 (2012).
2. Fominykh, P. Chernev, I. Zaharieva, J. Sicklinger, G. Stefanic, M. Doblinger, A. Muller, A. Pokharel, S. Bocklein, C. Scheu, T. Bein, and D. F. Rohifing, ACS. Nano. 5, 5180 (2015).
3. Ren, Z. Ma, and P. G. Bruce, Chem. Soc. Rev. 41, 4909 (2012).
4. Han, N. Chen, J. Zhang and L. Qu, Mater. Horiz. 4, 832 (2017)
5. W. Louie, and A.T. Bell, J. Am. Chem. Soc. 33, 12329 (2013).
6. -F. Li, and A. Selloni, ACS Catal. 4, 1148 (2014).
7. -I. Kim, Y.J. Sa, S.-H. Cho, I. So, K. Kwon, S.H. Joo, and J.-Y. Park, J. Electrochem. Soc.
163, F3020 (2016).
8. -S. So, N.-I. Kim, S.-H. Cho, Y.-R. Kim, J. Yoo, Y. Seo, Y.-S. Seo, B. Park, K. Kwon, and J.-Y. Park, J. Electrochem. Soc.
163, F3041 (2016).

Keywords: Oxygen evolution reaction; Oxygen reduction reaction; Bifunctional electrocatalyst; Unitized reversible fuel cell; Transition metal oxide.
Gold-Ruthenium Alloy Nanofibers As a Bifunctional Electrocatalyst for Overall Water Splitting in Acidic Environments
Authors: Kwon Taehui , Yu Areum , Lee Chongmok , Lee Youngmi 
Published: May 2020

Hydrogen is widely regarded as an environmentally-friendly and practical alternative energy to reduce reliance on fossil fuels. Also, hydrogen has the outstanding advantages of high energy storage density and sustainable reaction products. The most promising technology to produce hydrogen from abundant renewable sources is water electrolysis. Electrochemical water splitting involves two reaction systems, namely, an anodic oxygen evolution reaction (OER) and a cathodic hydrogen evolution reaction (HER). In general, typical HER catalysts with good activity in acidic solutions, such as Pt, exhibit poor activity in OER. Therefore, it is important to study bifunctional catalyst with high activity, efficiency and stability in acidic solutions.
In this presentation, we demonstrate the synthesis of AuRu alloy nanofibers as bifunctional electrocatalysts for water splitting. The Au/RuO2 nanocomposites are synthesized via electrospinning and calcination. After the subsequent reduction process, the AuRu alloy nanofibers are formed. The reduction process of Au/RuO2 nanocomposites to AuRu alloy nanofibers are investigated and the physical properties of AuRu alloy nanofibers in comparison to those of pure Au and Ru are analyzed with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The morphologies of the Au/RuO2 nanocomposites and AuRu alloy nanofibers are confirmed with field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The electrocatalytic activity of AuRu alloy nanofibers are studied toward both OER and HER in Ar-saturated 0.5 M H2SO4 aqueous solution with rotating disk electrode (RDE) voltammetry. The Tafel slopes which represent kinetics of the reaction for OER and HER are obtained based on the corresponding RDE curves. In summary, this study presents the AuRu alloy nanofibers as a better bifunctional electrocatalyst for overall water splitting than Au/RuO2, RuO2, Ru, Pt/C, Ir/C, Au/C and Ru/C.
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT& Future Planning (NRF-2017R1A2A2A14001137).
La, Ni-Based Metal Oxides As Bifunctional Catalysts for the Oxygen Reduction and Evolution Reactions in Alkaline Medium
Authors: Chen Jiyun 
Published: May 2020

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the fundamental processes occurring at the air electrode of metal-air batteries and reversible fuel cells. [1,2] However, the performance of those devices is hindered by the sluggish kinetics of both OER and ORR, and by the low stability and high cost of the catalysts. Here, we will present our recent studies on the one-dimensional (1D) La, Ni-based metal oxide [3] bifunctional catalysts which are characterized by excellent OER and ORR electrocatalytic activity and outstanding stability.
The catalysts were prepared by hydrothermal method and, by controlling the KOH concentration, 1D hydroxide precursors with different aspect ratios were synthesized. By using graphene (G) as the supporting material, a variety of La, Ni-based metal oxides such as Ni+La2O3/G, LaNiO3, and La2NiO4+NiO/G were synthesized, Figure 1. Electrochemical characterization of the catalysts showed that the aspect ratio of the materials has a significant effect on their electrocatalytic activity. Namely, Ni+La2O3/G nanorods have proven to be electrochemically active for ORR with a half-wave potential (E1/2) of 0.715 V vs RHE, and for OER with 1. 574 V vs RHE at 10.0 mA cm−2 (E10) in 0.1 M KOH. The performance of Ni+La2O3/G is close to that of commercial Pt/C (E1/2=0.830V) which is the most efficient catalyst of ORR, and significantly higher than commercial RuO2 (E10=1.633 V) and IrO2 (E10=1.663 V) for OER. The unique structural, morphological and electrocatalytic properties of the Ni+La2O3/G catalysts will be presented and discussed.
1. Sui, S.; Wang, X.; Zhou, X.; Su, Y.; Riffat, S.; Liu, C.-j., A comprehensive review of Pt electrocatalysts for the oxygen reduction reaction: Nanostructure, activity, mechanism and carbon support in PEM fuel cells. Journal of Materials Chemistry A 2017, 5 (5), 1808-1825.
2. Cheng, F.; Shen, J.; Peng, B.; Pan, Y.; Tao, Z.; Chen, J., Rapid room-temperature synthesis of nanocrystalline spinels as oxygen reduction and evolution electrocatalysts. Nature chemistry
2011,
3 (1), 79.
3. Singh, Sarika, Daria Zubenko, and Brian A. Rosen. "Influence of LaNiO3 shape on its solid-phase crystallization into coke-free reforming catalysts." ACS Catalysis 2016, 7 4199-4205.

Figure 1
The Path to Active and Stable Anion Exchange Membrane Water Electrolyzer
Authors: Faid Alaa Y , Barnett Alejandro Oyarce , Seland Frode , Sunde Svein 
Published: May 2020

Renewable hydrogen generation is a crucial step to reach a sustainable society. Water electrolysis represents a cheap and effective method for hydrogen production. Anion-exchange membranes (AEM) water electrolysis utilizes inexpensive transition metal electrocatalysts, membranes, ionomers, and construction materials.1
,
2 In this work we report characterization of NiMo and NiCoFe catalysts that have been optimized as hydrogen and oxygen evolution reaction (HER and OER) catalysts. The characterization includes studies of ionomer-electrolyte-catalyst interaction as a basis for optimizing HER and OER performance under real operating conditions. With these optimized catalysts in an AEM electrolyzer we have achieved 1 A cm-2 at 1.95 V in 1 M KOH at 50 oC. The AEM electrolyzer was stable for 65 hours at 0.5 A cm-2 in 0.1 M KOH. The catalysts developed here will be significant in supporting the pursuit of cheap hydrogen fuel.
References
1 A. Faid, A. Oyarce Barnett, F. Seland, S. Sunde, A. Y. Faid, A. Oyarce Barnett, F. Seland, and S. Sunde, Catalysts, 2018, 8, 614.
2 A. Y. Faid, A. O. Barnett, F. Seland, and S. Sunde, J. Electrochem. Soc., 2019, 166, F519–F533.

Figure 1