Competitor-Weighted Centrality and Small-World Clusters in Competition Networks on Firms' Innovation Ambidexterity: Evidence from the Wind Energy Industry.

A firm's embedding structures in a technology competition network can influence its propensity for innovation ambidexterity. Using PCT (patent cooperation treaty) patent data of wind energy companies between 2010 and 2019, we adopted social network analysis and fixed-effects panel negative binomial regression to examine the impacts of network structural features on firm innovation ambidexterity. The results show that competitor-weighted centrality contributes to a firm's propensities for both incremental and radical green innovation. In contrast, a firm's embeddedness in small-world clusters can moderate the effect of the firm's competitor-weighted centrality positively on its incremental innovation but negatively on its radical innovation. The study makes three theoretical contributions. First, it enriches the understanding of how the competition network affects innovation ambidexterity. Second, it provides new insights into the relationship between competition network structures and technology innovation strategy. Finally, it contributes to bridging the research on the social embeddedness perspective and green innovation literature. The findings of this study have important implications for enterprises in the wind energy sector regarding how competitive relationships affect green technology innovation. The study underscores the importance of considering the competitiveness of a firm's rivals and the embedded structural features when devising green innovation strategies.

Preparation of Alkali Activated Cementitious Material by Upgraded Fly Ash from MSW Incineration.

Utilization of municipal solid waste incineration fly ash (MSWI-FA) can avoid land occupation and environmental risks of landfill. In this paper, MSWI-FA was used to prepare alkali activated cementitious materials (AACMs) after two-step pretreatment. The ash calcination at 450 °C removed 93% of dioxins. The alkali washing with 0.2 g NaOH/g ash removed 89% of chlorine and retained almost 100% of calcium. The initial setting time of AACMs was too short to detect for 20% of MSWI-FA addition, and the prepared block had extensive cracks and expansion for CaClOH and CaSO4 inside. Alkaline washing pretreatment increased the initial setting time by longer than 3 min with 30% ash addition and eliminated the cracks and expansion. The significance of the factors for compressive strength followed the modulus of alkali activator > silica fume amount > alkaline washing MSWI fly ash (AW-MSWI-FA) amount. When the activator modulus was 1.2, 1.4 and 1.6, the blocks with 30% of AW-MSWI-FA had a compressive strength of up to 36.73, 32.61 and 16.06 MPa, meeting MU15 grade. The leaching test shows that these AACM blocks were not hazardous waste and almost no Zn, Cu, Cd, Pb, Ba, Ni, Be and Ag were released in the leaching solution.

Cu3P nanoparticle-reduced graphene oxide hybrid: an efficient electrocatalyst to realize N2-to-NH3 conversion under ambient conditions.

Industrial NH3 synthesis mainly relies on the Haber-Bosch process operated under harsh conditions. Ambient electrochemical N2 reduction offers an eco-friendly and sustainable pathway for NH3 synthesis, but its implementation depends on efficient electrocatalysts. Here, we report that a Cu3P nanoparticle-reduced graphene oxide (Cu3P-rGO) hybrid serves as an efficient electrocatalyst toward NH3 synthesis. Tested in 0.1 M HCl, Cu3P-rGO exhibits a large NH3 yield of 26.38 µg h-1 mgcat.-1 and a high faradaic efficiency of 10.11% at -0.45 V vs. the reversible hydrogen electrode, with high electrochemical stability. Theoretical calculations reveal that Cu3P can efficiently catalyze NH3 synthesis.

Electrocatalytic N2-to-NH3 conversion with high faradaic efficiency enabled using a Bi nanosheet array.

Electrocatalytic N2 reduction represents a promising alternative to the conventional Haber-Bosch process for ambient N2-to-NH3 fixation, but it is severely challenged by competitive hydrogen evolution, which limits the current efficiency for NH3 formation. In this work, a nanosheet array of metallic Bi, an environmentally benign elemental substance previously predicted theoretically to have low hydrogen-evolving activity, is proposed as a superior catalyst for N2 reduction electrocatalysis. Electrochemical tests show that the Bi nanosheet array on Cu foil as a stable 3D catalyst electrode achieves a high faradaic efficiency of 10.26% with an NH3 yield rate of 6.89 × 10-11 mol s-1 cm-2 at -0.50 V vs. the reversible hydrogen electrode in 0.1 M HCl, rivalling the performances of most reported noble-metal-free catalysts operating in acids. Density functional theory calculations suggest that Bi effectively activates the N[triple bond, length as m-dash]N bond and the alternating mechanism is energetically favourable.

Boosting electrocatalytic N2 reduction to NH3 on ß-FeOOH by fluorine doping.

As the cheapest and one of the most abundant transition metals, Fe is not only involved in nitrogenases for biological N2 fixation but is also extensively utilized in the Haber-Bosch process for industrial-scale NH3 synthesis. However, the application of Fe-based electrocatalysts for ambient N2-to-NH3 conversion still requires exploration of effective strategies to boost the catalytic performances for simultaneously achieving a large NH3 yield and a high Faradaic efficiency (FE). Here, we report that the ambient electrocatalytic N2 reduction activity of a ß-FeOOH nanorod can be greatly improved by fluorine doping. When tested at -0.60 V vs. reversible hydrogen electrode (RHE) in 0.5 M LiClO4, such a ß-FeO(OH,F) nanorod obtains an optimal NH3 yield (42.38 µg h-1 mgcat.-1) and FE (9.02%), much higher than those of pristine ß-FeOOH (10.01 µg h-1 mgcat.-1, 2.16%). Density functional theory calculations reveal that the enhancement in activity originates from the lower reaction energy barrier (0.24 eV) of the nanorod than that of ß-FeOOH (0.59 eV).

Sulfur-doped graphene for efficient electrocatalytic N2-to-NH3 fixation.

Industrial NH3 synthesis mainly relies on the carbon-emitting Haber-Bosch process operating under severe conditions. Electrocatalytic N2-to-NH3 fixation under ambient conditions is an attractive approach to reduce energy consumption and avoid direct carbon emission. In this communication, sulfur-doped graphene (S-G) is proposed as an efficient and stable electrocatalyst to drive the nitrogen reduction reaction (NRR) under ambient conditions. In 0.1 M HCl, this S-G attains a remarkably large NH3 yield of 27.3 µg h-1 mgcat.-1 and a high Faradaic efficiency of 11.5% at -0.6 and -0.5 V vs. a reversible hydrogen electrode, respectively, much higher than those of undoped G (6.25 µg h-1 mgcat.-1; 0.52%). Density functional theory calculations reveal that carbon atoms close to substituted sulfur atoms are the underlying catalytic active sites for the NRR on S-G, and the related NRR mechanism is also explored.

Recent Advances in the Development of Water Oxidation Electrocatalysts at Mild pH.

Developing anodic oxygen evolution reaction (OER) electrocatalysts with high catalytic activities is of great importance for effective water splitting. Compared with the water-oxidation electrocatalysts that are commonly utilized in alkaline conditions, the ones operating efficiently under neutral or near neutral conditions are more environmentally friendly with less corrosion issues. This review starts with a brief introduction of OER, the importance of OER in mild-pH media, as well as the fundamentals and performance parameters of OER electrocatalysts. Then, recent progress of the rational design of electrocatalysts for OER in mild-pH conditions is discussed. The chemical structures or components, synthetic approaches, and catalytic performances of the OER catalysts will be reviewed. Some interesting insights into the catalytic mechanism are also included and discussed. It concludes with a brief outlook on the possible remaining challenges and future trends of neutral or near-neutral OER electrocatalysts. It hopefully provides the readers with a distinct perspective of the history, present, and future of OER electrocatalysts at mild conditions.

Sulfur dots-graphene nanohybrid: a metal-free electrocatalyst for efficient N2-to-NH3 fixation under ambient conditions.

NH3 is an important chemical with a wide range of applications, but its synthesis mainly relies upon the harsh Haber-Bosch process with huge CO2 emission. Electrochemical N2 reduction offers a carbon-neutral process to convert N2 to NH3 under ambient conditions, but it requires efficient and stable catalysts to drive the N2 reduction reaction. Herein, we report that a sulfur dots-graphene nanohybrid acts as a metal-free electrocatalyst for ambient N2-to-NH3 conversion with excellent selectivity. When operated in 0.5 M LiClO4, this electrocatalyst achieves a large NH3 yield of 28.56 µg h-1 mgcat.-1 and a high Faradaic efficiency of 7.07% at -0.85 V vs. reversible hydrogen electrode. Notably, it also shows good electrochemical stability.

Biomass-derived oxygen-doped hollow carbon microtubes for electrocatalytic N2-to-NH3 fixation under ambient conditions.

Electrocatalytic N2 reduction as an alternative approach to the energy-intensive and large CO2-producing Haber-Bosch process for NH3 synthesis under mild conditions has attracted extensive attention. Current research efforts on N2 reduction have mainly focused on metal-based catalysts, but metal-free alternatives can avoid the issue of metal ion release. In this work, oxygen-doped hollow carbon microtubes (O-KFCNTs) derived from natural kapok fibers are reported as a metal-free NRR electrocatalyst for N2-to-NH3 conversion with excellent selectivity. In 0.1 M HCl, the O-KFCNTs achieve a high faradaic efficiency of 9.1% at -0.80 V vs. a reversible hydrogen electrode (RHE) and a NH3 yield rate of 25.12 µg h-1 mgcat.-1 at -0.85 V vs. RHE under ambient conditions. Notably, this catalyst also demonstrates high stability.

Mid-infrared Plasmonic Circular Dichroism Generated by Graphene Nanodisk Assemblies.

It is very interesting to bring plasmonic circular dichroism spectroscopy to the mid-infrared spectral interval, and there are two reasons for this. This spectral interval is very important for thermal bioimaging, and simultaneously, this spectral range includes vibrational lines of many chiral biomolecules. Here we demonstrate that graphene plasmons indeed offer such opportunity. In particular, we show that chiral graphene assemblies consisting of a few graphene nanodisks can generate strong circular dichroism (CD) in the mid-infrared interval. The CD signal is generated due to the plasmon-plasmon coupling between adjacent nanodisks in the specially designed chiral graphene assemblies. Because of the large dimension mismatch between the thickness of a graphene layer and the incoming light's wavelength, three-dimensional configurations with a total height of a few hundred nanometers are necessary to obtain a strong CD signal in the mid-infrared range. The mid-infrared CD strength is mainly governed by the total dimensions (total height and helix scaffold radius) of the graphene nanodisk assembly and by the plasmon-plasmon interaction strength between its constitutive nanodisks. Both positive and negative CD bands can be observed in the graphene assembly array. The frequency interval of the plasmonic CD spectra overlaps with the vibrational modes of some important biomolecules, such as DNA and many different peptides, giving rise to the possibility of enhancing the vibrational optical activity of these molecular species by attaching them to the graphene assemblies. Simultaneously the spectral range of chiral mid-infrared plasmons in our structures appears near the typical wavelength of the human-body thermal radiation, and therefore, our chiral metastructures can be potentially utilized as optical components in thermal imaging devices.