Concluding remarks: Sustainable nitrogen activation - are we there yet?

The activation of dinitrogen as a fundamental step in reactions to produce nitrogen compounds, including ammonia and nitrates, has a cornerstone role in chemistry. Bringing together research from disparate fields where this can be achieved sustainably, this Faraday Discussion seeks to build connections between approaches that can stimulate further advances. In this paper we set out to provide an overview of these different approaches and their commonalities. We explore experimental aspects including the positive role of increasing nitrogen pressure in some fields, as well as offering perspectives on when 15N2 experiments might, and might not, be necessary. Deconstructing the nitrogen reduction reaction, we attempt to provide a common framework of energetic scales within which all of the different approaches and their components can be understood. On sustainability, we argue that although green ammonia produced from a green-H2-fed Haber-Bosch process seems to fit the bill, there remain many real-world contexts in which other, sustainable, approaches to this vital reaction are urgently needed.

A Survey of Catalytic Materials for Ammonia Electrooxidation to Nitrite and Nitrate.

Studies of the ammonia oxidation reaction (AOR) for the synthesis of nitrite and nitrate (NO2/3 - ) have been limited to a small number of catalytic materials, majorly Pt based. As the demand for nitrate-based products such as fertilisers continues to grow, exploration of alternative catalysts is needed. Herein, 19 metals immobilised as particles on carbon fibre electrodes were tested for their catalytic activity for the ammonia electrooxidation to NO2/3 - under alkaline conditions (0.1 m KOH). Nickel-based electrodes showed the highest overall NO2/3 - yield with a rate of 5.0±1.0 nmol s-1 cm-2 , to which nitrate contributed 62±8 %. Cu was the only catalyst that enabled formation of nitrate, at a rate of 1.0±0.4 nmol s-1 cm-2 , with undetectable amounts of nitrite produced. Previously unexplored in this context, Fe and Ag also showed promise and provided new insights into the mechanisms of the process. Ag-based electrodes showed strong indications of activity towards NH3 oxidation in electrochemical measurements but produced relatively low NO2/3 - yields, suggesting the formation of alternate oxidation products. NO2/3 - production over Fe-based electrodes required the presence of dissolved O2 and was more efficient than with Ni on longer timescales. These results highlight the complexity of the AOR mechanism and provide a broad set of catalytic activity and nitrate versus nitrite yield data, which might guide future development of a practical process for the distributed sustainable production of nitrates and nitrites at low and medium scales.

High-Performance Magnesium Electrochemical Cycling with Hybrid Mg-Li Electrolytes.

Kinetics and coulombic efficiency of the electrochemical magnesium plating and stripping processes are to a significant extent defined by the composition of the electrolyte solution, optimization of which presents a pathway for improved performance. Adopting this strategy, we undertook a systematic investigation of the Mg0/2+ process in different combinations of the Mg2+-Li+-borohydride-bis(trifluoromethylsulfonyl)imide (TFSI-) electrolytes in 1,2-dimethoxyethane (DME) solvent. Results indicate that the presence of BH4- is essential for high coulombic efficiency, which coordination to Mg2+ was confirmed by Raman and NMR spectroscopic analysis. However, the high rates observed also require the presence of Li+ and a supplementary anion such as TFSI-. The Li+ + BH4- + TFSI- combination of ionic species prevents passivation of the magnesium surface and thereby enables efficient Mg0/2+ electrochemical cycling. The best Mg0/2+ performance with the stabilized coulombic efficiency of 88 ± 1% and one of the highest deposition/stripping rates at ambient temperature reported to date are demonstrated at an optimal [Mg(BH4)2]:[LiTFSI] mole ratio of 1:2.

Opening the Pathway: An Example of Universal Design for Learning as a Guide to Inclusive Teaching Practices.

Universal Design for Learning (UDL) provides a flexible framework for supporting a wide variety of learners. We report here on a conference that presented the UDL framework as a way to increase success of deaf and hard-of-hearing (deaf/hh) students in introductory biology courses. The Opening the Pathway conference was an NSF Advanced Technological Education project focusing on raising awareness about careers in biotechnology and student success in introductory biology, a key gateway course for careers in biotechnology. The participants were professionals who work with deaf/hh students at pivotal points in students' educational pathways for raising awareness of biotechnology career options, including community college faculty, high school faculty at schools for the deaf, and American Sign Language (ASL) interpreters. The conference goal was to provide an effective, meaningful professional development experience in biology instruction. The conference explicitly addressed the role of a UDL approach in building accessible, inclusive, productive learning environments, particularly for deaf/hh students, and demonstrated how to make effective pedagogical practices, specifically case-based learning, inclusive and UDL-aligned in an introductory biology context. We describe the conference, conference outcomes for participants, and in particular the application of the UDL framework to create an inclusive experience.

Copper-Catalyzed Electrosynthesis of Nitrite and Nitrate from Ammonia: Tuning the Selectivity via an Interplay Between Homogeneous and Heterogeneous Catalysis.

Electrocatalytic oxidation of ammonia is an appealing, low-temperature process for the sustainable production of nitrites and nitrates that avoids the formation of pernicious N2 O and can be fully powered by renewable electricity. Currently, however, the number of known efficient catalysts for such a reaction is limited. The present work demonstrates that copper-based electrodes exhibit high electrocatalytic activity and selectivity for the NH3 oxidation to NO2 - and NO3 - in alkaline solutions. Systematic investigation of the effects of pH and potential on the kinetics of the reaction using voltammetric analysis andin situ Raman spectroscopy suggest that ammonia electrooxidation on copper occurrs via two primary catalytic mechanisms. In the first pathway, NH3 is converted to NO2 - via a homogeneous electrocatalytic process mediated by redox transformations of aqueous [Cu(OH)4 ]-/2- species, which dissolve from the electrode. The second pathway is the heterogeneous catalytic oxidation of NH3 on the electrode surface favoring the formation of NO3 - . By virtue of its nature, the homogeneous-mediated pathway enables higher selectivity and was less affected by electrode poisoning with the strongly adsorbed "N" intermediates that have plagued the electrocatalytic ammonia oxidation field. Thus, the selectivity of the Cu-catalyzed NH3 oxidation towards either nitrite or nitrate can be achieved through balancing the kinetics of the two mechanisms by adjusting the pH of the electrolyte medium and potential.

Opportunities and challenges for savanna burning emissions abatement in southern Africa.

Savanna fires occurring in sub-Saharan Africa account for over 60% of global fire extent, of which more than half occurs in the Southern Hemisphere contributing ~29% of global fire emissions. Building on experience in reducing savanna fire emissions in fire-prone north Australian savannas through implementation of an internationally accredited 'savanna burning' emissions abatement methodology, we explore opportunities and challenges associated with the application of a similar approach to incentivise emissions reduction in fire-prone southern African savannas. We first show that for a focal region covering seven contiguous countries, at least 80% of annual savanna large fire (>250 ha) extent and emissions occur under relatively severe late dry season (LDS) fire-weather conditions, predominantly in sparsely inhabited areas. We then assess the feasibility of adapting the Australian emissions abatement methodology through exploratory field studies at the Tsodilo Hills World Heritage site in north-west Botswana, and the Niassa Special Reserve in northern Mozambique. Our assessment demonstrates that application of a savanna burning emissions abatement method focused on the undertaking of strategically located early dry season (EDS) burning to reduce LDS wildfire extent and resultant emissions meets key technical criteria, including: LDS fine fuels tend to be markedly greater than EDS fuels given seasonal leaf litter inputs; LDS fires tend to be significantly more severe and combust more fuels; methane and nitrous oxide emission factors are essentially equivalent in EDS and LDS periods under cured fuel conditions. In discussion we consider associated key implementation challenges and caveats that need to be addressed for progressing development of savanna burning methods that incentivise sustainable fire management, reduce emissions, and support community livelihoods in wildfire-dominated southern African savannas.

Antarctica and the strategic plan for biodiversity.

The Strategic Plan for Biodiversity, adopted under the auspices of the Convention on Biological Diversity, provides the basis for taking effective action to curb biodiversity loss across the planet by 2020-an urgent imperative. Yet, Antarctica and the Southern Ocean, which encompass 10% of the planet's surface, are excluded from assessments of progress against the Strategic Plan. The situation is a lost opportunity for biodiversity conservation globally. We provide such an assessment. Our evidence suggests, surprisingly, that for a region so remote and apparently pristine as the Antarctic, the biodiversity outlook is similar to that for the rest of the planet. Promisingly, however, much scope for remedial action exists.