Understanding the high activity of mildly reduced graphene oxide electrocatalysts in oxygen reduction to hydrogen peroxide

The direct electrochemical synthesis of hydrogen peroxide (H2O2) would provide an attractive alternative to the traditional anthraquinone oxidation process for continuous on-site applications. Its industrial viability depends greatly on developing cost-effective catalysts with high activity and selectivity. Recent experiments have demonstrated that mildly reduced graphene oxide (mrGO) electrocatalysts exhibit highly selective and stable H2O2 formation activity [e.g., H. W. Kim, M. B. Ross, N. Kornienko, L. Zhang, J. Guo, P. Yang and B. D. McCloskey, Nat. Catal., 2018, 1, 282-290]. However, the identification of active site structures for this catalytic process on mrGO is doubtful. Herein, by means of first-principles calculations, we examine the H2O2 formation activities of the active site structures proposed in experiments and find that their activities are actually very low. Then, we systematically investigate the H2O2 formation activities of different oxygen functional group structures on mrGO based on experimental observations, and discover two types of oxygen functional group structures (2EP and 1ET + 1EP) that have comparable or even lower overpotentials (<0.10 V) for H2O2 formation compared with the state-of-the-art PtHg4 electrocatalyst. Our theoretical results reveal that the graphene edge and the synergetic effects between different oxygen functional groups are essential for the superior performance of mrGO for H2O2 production. This work not only provides a feasible explanation of the cause of high H2O2 formation activity of mrGO but also offers a guide for the design, synthesis, and mechanistic investigation of advanced carbon-based electrocatalysts for effective H2O2 production.This research was undertaken with the assistance of resources provided by the National Computational Infrastructure (NCI) facility at the Australian National University; allocated through both the National Computational Merit Allocation Scheme supported by the Australian Government and the Australian Research Council grant LE160100051 (Maintaining and enhancing merit-based access to the NCI National Facility, 2016–2018). The study was financed by an ARC Discovery Grant (DP170104853)

Electrocatalytic Reduction of Carbon Dioxide to Methane on Single Transition Metal Atoms Supported on a Defective Boron Nitride Monolayer: First Principle Study

The electrochemical conversion of carbon dioxide (CO2) and water into useful multi‐electron transfer products, such as methanol (CH3OH) and methane (CH4), is a major challenge in facilitating a closed carbon cycle. Here, a systematic first principle study of the potential of single transition metal atoms (Sc to Zn, Mo, Rh, Ru, Pd, Ag, Pt, and Au) supported on experimentally available defective boron nitride monolayers with a boron monovacancy (TM/defective BN) to achieve highly efficient electrocatalytic CO2 reduction (ECR) to CH4 is carried out. Our computations reveal that Fe/defective BN, Co/defective BN, and Pt/defective BN nanosheets possess outstanding ECR activities with quite low (less negative) onset potentials of −0.52, −0.68, and −0.60 V, respectively. Given that Fe and Co are nonprecious metals, Fe/defective BN and Co/defective BN may provide cost‐effective electrocatalysts. The high ECR activities of these TM/defective BN catalyst systems stem from the moderate electrocatalysts’ affinities for C and O, which modulate the free energies of ECR intermediates in the reaction pathways. Moreover, it is found that Fe/defective BN and Pt/defective BN show high selectivity of ECR to CH4. This finding highlights a strategy to design highly active and selective single‐atom electrocatalysts for ECR to CH4.S.S. and H.A. acknowledge the financial support by the Australian Research Council under Discovery Project (DP170104853). This research was undertaken with the assistance of resources provided by the National Computing Infrastructure facility at the Australian National University, allocated through both the National Computational Merit Allocation Scheme supported by the Australian Government and the Australian Research Council grant LE120100181 (Enhanced merit-based access and support at the new NCI petascale supercomputing facility, 2012–2015)

Diffusion of tin in germanium: a GGA+U approach

Density functional theory calculations are used to investigate the formation and diffusion of tin-vacancy pairs (SnV) in germanium (Ge). Depending upon the Fermi energy, SnV pairs can form in neutral, singly negative, or doubly negative charged states. The activation energies of diffusion, also as function of the Fermi energy, are calculated to lie between 2.48-3.65 eV, in agreement with and providing an interpretation of available experimental work

Mobile App Development Through Designing Structural Visual Method for Effective Learning Foreign Language

The world of the latest information technologies is taking an ever-increasing place in our life. Mobile technologies are becoming an integral part of modern culture, including in the field of education. It is thanks to mobile technologies that student's interest in the subject increases significantly, and their thinking activity is activated. Therefore, we need to create a fast and efficient automated system that allows increased interest of students to learn foreign language. With such a system, the learner controls the learning process and progress in his own space based on his cognitive state and learners can speak the target language without effort and psychological barriers. The Purpose of the research is to create interactive speech trainer system based on a structural and visual approach, will ensure the formation of stable foreign language skills of trainees on the background of the active use of visual representation of language and interactive speech technology, this system use a technique for applying the visual Approach and structural-visual method in the educational environment by transforming grammatical information from verbal to graphic form. In this article we will describe the ideas that will guide the design of this system and our steps to develop our proposed architecture based on a visual model as a platform in mobile application to provide the process of controlling the formation of speech skills and allowing the transition from foreign language learning to its improvement and acceleration

Diffusion of E centers in germanium predicted using GGA+U approach

Density functional theory calculations (based on GGA+U approach) are used to investigate the formation and diffusion of donor-vacancy pairs (E centers) in germanium. We conclude that depending upon the Fermi energy, E centers that incorporate for phosphorous and arsenic can form in their neutral, singly negatively or doubly negatively charged states whereas with antimony only the neutral or doubly negatively charged states are predicted. The activation energies of diffusion are compared with recent experimental work and support the idea that smaller donor atoms exhibit higher diffusion activation energies

Thermoelectric transport in strained Si and Si/Ge heterostructures

The anisotropic thermoelectric transport properties of bulk silicon strained in [111]-direction were studied by detailed first-principles calculations focussing on a possible enhancement of the power factor. Electron as well as hole doping were examined in a broad doping and temperature range. At low temperature and low doping an enhancement of the power factor was obtained for compressive and tensile strain in the electron-doped case and for compressive strain in the hole-doped case. For the thermoelectrically more important high temperature and high doping regime a slight enhancement of the power factor was only found under small compressive strain with the power factor overall being robust against applied strain. To extend our findings the anisotropic thermoelectric transport of an [111]-oriented Si/Ge superlattice was investigated. Here, the cross-plane power factor under hole-doping was drastically suppressed due to quantum-well effects, while under electron-doping an enhanced power factor was found. With that, we state a figure of merit of ZT$=0.2$ and ZT$=1.4$ at T=\unit[300]{K} and T=\unit[900]{K} for the electron-doped [111]-oriented Si/Ge superlattice. All results are discussed in terms of band structure features

Implementation Mobile App for Foreign Language Acquisition Based on Structural Visual Method

Among all modern communication devices, mobile phones are the most powerful means of communication even richer than e-mail or chat, as it can act as a teaching device despite its technical limitations. Therefore, we need to create a fast and efficient automated system that allow increased interest of students to learn foreign language, which provides the cognitive activity of students, stimulates and develops cognitive processes: thinking, perception, and memory. With such a system, the learner controls the learning process and progress in his own space based on his cognitive state, and learners can speak the target language without effort and psychological barriers. The purpose of the research is to create interactive speech trainer system based on a structural and visual approach and to ensure the formation of stable foreign language skills of trainees on the background of the active use of visual representation of language and interactive speech technology, and this system uses a technique for applying the visual approach and structural visual method in the educational environment by transforming grammatical information from verbal to graphic form and replacing complex text rules with appropriate visual structures in the form of pictures, schemes, and diagrams. We present our steps to implement our proposed architecture based on a visual model as a platform in mobile application with the establishment of content management system to provide the process of controlling the formation of speech skills and allowing the transition from foreign language learning to its improvement and acceleration. We also describe the ideas that will guide the design of this system

Implementation Mobile App for Foreign Language Acquisition Based on Structural Visual Method

Among all modern communication devices, mobile phones are the most powerful means of communication even richer than e-mail or chat, as it can act as a teaching device despite its technical limitations. Therefore, we need to create a fast and efficient automated system that allow increased interest of students to learn foreign language, which provides the cognitive activity of students, stimulates and develops cognitive processes: thinking, perception, and memory. With such a system, the learner controls the learning process and progress in his own space based on his cognitive state, and learners can speak the target language without effort and psychological barriers. The purpose of the research is to create interactive speech trainer system based on a structural and visual approach and to ensure the formation of stable foreign language skills of trainees on the background of the active use of visual representation of language and interactive speech technology, and this system uses a technique for applying the visual approach and structural visual method in the educational environment by transforming grammatical information from verbal to graphic form and replacing complex text rules with appropriate visual structures in the form of pictures, schemes, and diagrams. We present our steps to implement our proposed architecture based on a visual model as a platform in mobile application with the establishment of content management system to provide the process of controlling the formation of speech skills and allowing the transition from foreign language learning to its improvement and acceleration. We also describe the ideas that will guide the design of this system