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1. Sequestration of solid carbon in concrete: A large-scale enabler of lower-carbon intensity hydrogen from natural gas

   https://doi.org/10.1557/s43577-021-00118-z  

   Li, Jiaqi ; Spanu, Leonardo ; Heo, Jeffrey ; Zhang, Wenxin ; Gardner, David W. ; Carraro, Carlo ; Maboudian, Roya ; Monteiro, Paulo J. ( August 2021 , MRS Bulletin)

   Abstract Methane pyrolysis is an emerging technology to produce lower-carbon intensity hydrogen at scale, as long as the co-produced solid carbon is permanently captured. Partially replacing Portland cement with pyrolytic carbon would allow the sequestration at a scale that matches the needs of the H 2 industry. Our results suggest that compressive strength, the most critical mechanical property, of blended cement could even be improved while the cement manufacture, which contributes to ~ 9% global anthropogenic CO 2 emissions, can be decarbonized. A CO 2 abatement up to 10% of cement production could be achieved with the inclusion of selected carbon morphologies, without the need of significant capital investment and radical modification of current production processes. The use of solid carbon could have a higher CO 2 abatement potential than the incorporation of conventional industrial wastes used in concrete at the same replacement level. With this approach, the concrete industry could become an enabler for manufacturing a lower-carbon intensity hydrogen in a win–win solution. Impact Methane pyrolysis is an up-scalable technology that produces hydrogen as a lower carbon-intensity energy carrier and industrial feedstock. This technology can attract more investment for lower-carbon intensity hydrogen if co-produced solid carbon (potentially hundreds of millionmore »tons per year) has value-added applications. The solid carbon can be permanently stored in concrete, the second most used commodity worldwide. To understand the feasibility of this carbon storage strategy, up to 10 wt% of Portland cement is replaced with disk-like or fibrillar carbon in our study. The incorporation of 5% and 10% fibrillar carbons increase the compressive strength of the cement-based materials by at least 20% and 16%, respectively, while disk-like carbons have little beneficial effects on the compressive strength. Our life-cycle assessment in climate change category results suggest that the 10% cement replacement with the solid carbon can lower ~10% of greenhouse gas emissions of cement production, which is currently the second-largest industrial emitter in the world. The use of solid carbon in concrete can supplement the enormous demand for cement substitute for low-carbon concrete and lower the cost of the low-carbon hydrogen production. This massively available low-cost solid carbon would create numerous new opportunities in concrete research and the industrial applications.« less
2. Cement substitution with secondary materials can reduce annual global CO2 emissions by up to 1.3 gigatons

   https://doi.org/10.1038/s41467-022-33289-7  

   Shah, Izhar Hussain ; Miller, Sabbie A. ; Jiang, Daqian ; Myers, Rupert J. ( September 2022 , Nature Communications)

   Population and development megatrends will drive growth in cement production, which is already one of the most challenging-to-mitigate sources of CO₂emissions. However, availabilities of conventional secondary cementitious materials (CMs) like fly ash are declining. Here, we present detailed generation rates of secondary CMs worldwide between 2002 and 2018, showing the potential for 3.5 Gt to be generated in 2018. Maximal substitution of Portland cement clinker with these materials could have avoided up to 1.3 Gt CO₂-eq. emissions (~44% of cement production and ~2.8% of anthropogenic CO₂-eq. emissions) in 2018. We also show that nearly all of the highest cement producing nations can locally generate and use secondary CMs to substitute up to 50% domestic Portland cement clinker, with many countries able to potentially substitute 100% Portland cement clinker. Our results highlight the importance of pursuing regionally optimized CM mix designs and systemic approaches to decarbonizing the global CMs cycle.
3. Transparent InGaZnO-Based Resistive Random Access Memory

   Qin, Fei ; Lee, Sunghwan ( May 2022 , Materials Research Society)

   The major focus of artificial intelligence (AI) research is made on biomimetic synaptic processes that are mimicked by functional memory devices in the computer industry [1]. It is urgent to find a memory technology for suiting with Brain-Inspired Computing to break the von Neumann bottleneck which limits the efficiency of conventional computer architectures [2]. Silicon-based flash memory, which currently dominates the market for data storage devices, is facing challenging issues to meet the needs of future data storage device development due to the limitations, such as high-power consumption, high operation voltage, and low retention capacity [1]. The emerging resistive random-access memory (RRAM) has elicited intense research as its simple sandwiched structure, including top electrode (TE) layer, bottom electrode (BE) layer, and an intermediate resistive switching (RS) layer, can store data using RS phenomenon between the high resistance state (HRS) and the low resistance state (LRS). This class of emerging devices is expected to outperform conventional memory devices [3]. Specifically, the advantages of RRAM include low-voltage operation, short programming time, great cyclic stability, and good scalability [4]. Among the materials for RS layer, indium gallium zinc oxide (IGZO) has attracted attention because of its abundance and high atomic diffusion property ofmore »oxygen atoms, transparency, and its easily modulated electrical properties by controlling the stoichiometric ratio of indium and gallium as well as oxygen potential in the sputter gas [5, 6]. Moreover, since the IGZO can be applied to both the thin-film transistor (TFT) channel and RS layer, the IGZO-based fully integrated transparent electronics are very promising [5]. In this work, we proposed transparent IGZO-based RRAMs. First, we chose ITO to serve as both TE and BE to achieve high transmittance in the visible regime of light. All three layers (TE, RS, BE layers) were deposited using a multi-target magnetron sputtering system on glass substrates to demonstrate fully transparent oxide-based devices. I-V characteristics were evaluated by a semiconductor parameter analyzer, and our devices showed typical butterfly curves indicating the bipolar RS property. And the IGZO-based RRAM can survive more than 50 continuous sweeping cycles. The optical transmission analysis was carried out via an UV-Vis spectrometer and the average transmittance around 80% out of entire devices in the visible-light wavelength range, implying high transparency. To investigate the thickness dependence on the properties of RS layer, 50nm, 100nm and 150nm RS layer of IGZO RRAM were fabricated. Also, the oxygen partial pressure during the sputtering of IGZO was varied to optimize the property because the oxygen vacancy concentration governs the RS and RRAM performance. Electrode selection is crucial and can impact the performance of the whole device [7]. Thus, Cu TE was chosen for our second type of device because the diffusion of Cu ions can be beneficial for the formation the conductive filament (CF). Finally, a ~5 nm SiO2 barrier layer was employed between TE and RS layers to confine the diffusion of Cu into the RS layer. At the same time, this SiO2 inserting layer can provide an additional interfacial series resistance in the device to lower the off current, consequently, improve the on/off ratio and whole performance. In conclusion, the transparent IGZO-based RRAMs were established. To tune the property of RS layer, the thickness layer and sputtering conditions of RS were adjusted. In order to engineer the diffusion capability of the TE material to the RS layer and the BE, a set of TE materials and a barrier layer were integrated in IGZO-based RRAM and the performance was compared. Our encouraging results clearly demonstrate that IGZO is a promising material in RRAM applications and overcoming the bottleneck of current memory technologies.« less
4. Enzymatic synthesis of supported CdS quantum dot/reduced graphene oxide photocatalysts

   https://doi.org/10.1039/C9GC00097F  

   Spangler, Leah C. ; Cline, Joseph P. ; Sakizadeh, John D. ; Kiely, Christopher J. ; McIntosh, Steven ( July 2019 , Green Chemistry)

   Photocatalysis is an attractive, sustainable, and potentially low-cost route to capture solar energy as fuel. However, current photocatalytic materials synthesis routes are not easily scaled-up to the magnitude required to impact our energy consumption due to both economic and environmental concerns. While the elements utilized are often earth abundant, typical synthetic routes utilize organic solvents at elevated temperatures with relatively expensive precursors. Herein, we demonstrate the fully biomineralized synthesis of a quantum confined CdS/reduced graphene oxide (CdS/rGO) photocatalyst catalyzed by the single enzyme cystathionine γ-lyase (CSE). The synthesis is performed at pH 9 in a buffered aqueous solution, under ambient conditions, and utilizes the low-cost precursors Cd acetate, l -cysteine, graphene oxide, and a poly- l -lysine linker molecule. CSE actively decomposes l -cysteine to generate reactive HS − in aqueous solution at pH 9. Careful selection and control of the synthesis conditions enable both reduction of graphene oxide to rGO, and control over the mean CdS nanocrystal size. The CdS is conjugated to the rGO via a poly- l -lysine crosslinker molecule introduced during rGO formation. The completed CdS/rGO photocatalyst is capable of producing H 2 , without the aid of a noble metal co-catalyst, at a rate ofmore »550 μmol h −1 g −1 for an optimized CdS/rGO ratio. This rate is double that measured for unsupported CdS and is comparable to CdS/rGO photocatalysts produced using more typical chemical synthesis routes. Single enzyme biomineralization by CSE can produce a range of metal chalcogenides without altering the enzyme or benign approach, making this an easily adaptable procedure for the sustainable production of a wide variety of important photocatalyst systems.« less
5. Avian Coloration Genetics: Recent Advances and Emerging Questions

   https://doi.org/10.1093/jhered/esab015  

   Price-Waldman, Rosalyn ; Stoddard, Mary Caswell ( May 2021 , Journal of Heredity)

   vonHoldt, Bridgett (Ed.)

   Abstract The colorful phenotypes of birds have long provided rich source material for evolutionary biologists. Avian plumage, beaks, skin, and eggs—which exhibit a stunning range of cryptic and conspicuous forms—inspired early work on adaptive coloration. More recently, avian color has fueled discoveries on the physiological, developmental, and—increasingly—genetic mechanisms responsible for phenotypic variation. The relative ease with which avian color traits can be quantified has made birds an attractive system for uncovering links between phenotype and genotype. Accordingly, the field of avian coloration genetics is burgeoning. In this review, we highlight recent advances and emerging questions associated with the genetic underpinnings of bird color. We start by describing breakthroughs related to 2 pigment classes: carotenoids that produce red, yellow, and orange in most birds and psittacofulvins that produce similar colors in parrots. We then discuss structural colors, which are produced by the interaction of light with nanoscale materials and greatly extend the plumage palette. Structural color genetics remain understudied—but this paradigm is changing. We next explore how colors that arise from interactions among pigmentary and structural mechanisms may be controlled by genes that are co-expressed or co-regulated. We also identify opportunities to investigate genes mediating within-feather micropatterning and the coloration ofmore »bare parts and eggs. We conclude by spotlighting 2 research areas—mechanistic links between color vision and color production, and speciation—that have been invigorated by genetic insights, a trend likely to continue as new genomic approaches are applied to non-model species.« less