Rational design of single‐atom catalyst (SAC) presents a promising route to precise heterogeneous catalysis, yet it requires us to understand the catalytic activity that often can be correlated with ...the adsorption energies. Here, we investigate the hydrogen adsorption on a series of 3d transition metal (TM) SACs anchored on the N4‐coordination site of N‐doped graphene (MN4/C), and find that the adsorption energies present a volcano curve that violates the d‐band theory. By decomposing the adsorption energies into two distinctive contributions, i. e., the orbital interaction (ΔEorbit
) and electrostatic interaction (ΔEelstat
), we find that it is the competition between the two that results in the volcano curve. We further identify that the trend of ΔEorbit
is dictated by the TM 4 s orbital that is governed by bonding with the substrate, while ΔEelstat
is regulated by the charge transfer from TM single‐atom to the N4/C substrate, which originates mainly from the bonding between the TM 3dxy orbital and the substrate. Furthermore, we establish the intrinsic dipole moment of active site as a quantitative descriptor for both ΔEorbit
and ΔEelstat
in the adsorption on MN4/C, and apply it to understanding the trends of adsorption energies on 4d and 5d TM‐based MN4/C SACs. Our findings provide deep insights into understanding the adsorption and thus the catalytic activity on TM‐based SACs.
Adsorption on single‐atom catalyst: The adsorption energies of the hydrogen atom on the MN4/C single‐atom catalysts present a volcano curve that violates the d‐band theory, and it arises from the competition between the orbital (ΔEorbit
) and electrostatic (ΔEelstat
) interactions. The intrinsic dipole moment of active site is found to be a quantitative descriptor of the competition and thus the adsorption trend.
MXenes are becoming a worthy contender for boosting the efficacy of semiconductor photocatalysts because of their rich surface and electronic properties, which is exemplified to be a dynamic yet ...open‐ended exploration of the materials space. Herein, the promise that MXenes hold for photocatalytic applications is elucidated by presenting the various roles of MXenes in the preparation of composite photocatalysts and enhancing their activity and stability. A specific focus is put on the key issues that should be taken into account when utilizing the specific function of MXenes and the strategies to deliver the great potential of MXenes into better play. The discussion is based on different aspects closely related to the flexible surface and electronic features of MXenes, including their morphology control, stability issue, and electronic structure mutability with the purpose to present an objective and comprehensive scenario of MXenes for photocatalysis. Finally, some noteworthy research directions for the future development of MXenes‐based photocatalytic systems are outlined and prospected. This review is expected to provide a useful scaffold for the rational design and synthesis of efficient and stable MXenes‐based photocatalysts by objectively understanding and taming the functional vitality of MXenes.
MXenes with tunable surface and electronic properties have aroused ever‐increasing interests in the field of photocatalysis. This review elucidates the promise that MXenes hold for constructing composite photocatalyst with enhanced activity and stability. In addition, some key issues are discussed in detail to provide an objective and comprehensive overview of MXenes for photocatalysis.
Live streaming is conducive to consumers obtaining rich and accurate product information, by displaying products through real-time video technology. Live streaming provides a new type of product ...presentation method, such as showing products from different perspectives, interacting with consumers by trying the products out, and answering consumers' questions in real time. Other than the current research focus on anchors (or influencers) and consumers in live-streaming marketing, this article tried to explore the way of the product presentation and its effect and mechanism on consumers' purchase intention. Three studies were conducted. Study 1 (
= 198, 38.4% male) used a survey to explore the main effect of product presentation on consumers' purchase intention and the mediating effect of the perceived product value. Study 2 (
= 60, 48.3% male) was a survey-based behavioral experiment, and it tested the above effects in the scenario of food consumption. Study 3 (
= 118, 44.1% men) tried to deeply discuss the above relationship in the appeal consumption scenario by priming different levels of the product presentation and time pressure. The results found that the product presentation positively affected consumers' purchase intention. The perceived product value played a mediating role in the relationship between product presentation and purchase intention. In addition, different levels of time pressure in the living room moderated the above mediation effect. When time pressure is high, the positive impact of product presentation on purchase intention is strengthened. This article enriched the theoretical research on product presentation by exploring product presentation in the context of live-streaming marketing. It explained how product presentation could improve consumers' perceived product value and the boundary effect of time pressure on consumers' purchase intention. In practice, this research guided brands and anchors on designing product displays to improve consumers' purchase decisions.
Despite remarkable progress in hybrid perovskite solar cells (PSCs), the concern of toxic lead ions remains a major hurdle in the path towards PSC's commercialization; tin (Sn)‐based PSCs outperform ...the reported Pb‐free perovskites in terms of photovoltaic performance. However, it is of a particularly great challenge to develop effective passivation strategies to suppress Sn(II) induced defect densities and oxidation for attaining high‐performance all‐inorganic CsSnI3 PSCs. Herein, a facile yet effective thioamides passivation strategy to modulate defect state density at surfaces and grain boundaries in CsSnI3 perovskites is reported. The thiosemicarbazide (TSC) with SCN functional groups can make strong coordination interaction with charge defects, leading to enhanced electron cloud density around defects and increased vacancy formation energies. Importantly, the surface passivation can reduce the deep level trap state defect density originated from undercoordinated Sn2+ ion and Sn2+ oxidation, significantly restraining nonradiative recombination and elongating the carrier lifetime of TSC treated CsSnI3 PSCs. The surface passivated all‐inorganic CsSnI3 PSCs based on an inverted configuration delivers a champion power conversion efficiency (PCE) of 8.20%, with a prolonged lifetime over 90% of initial PCE, after 500 h of continuous illumination. The present strategy sheds light on surface defect passivation for achieving highly efficient all‐inorganic lead‐free Sn‐based PSCs.
A facile yet effective thioamides passivation strategy is proposed to suppress defects at the surface and grain boundary of CsSnI3 perovskite, which reduces the deep level trap density from undercoordinated Sn2+ and Sn2+ oxidation. The surface passivated CsSnI3 perovskite solar cell (PSC) delivers a efficiency of 8.20% which is the highest among all lead‐free all‐inorganic PSCs.
As low-cost electrocatalysts for oxygen reduction reaction applied to fuel cells and metal-air batteries, atomic-dispersed transition metal-nitrogen-carbon materials are emerging, but the genuine ...mechanism thereof is still arguable. Herein, by rational design and synthesis of dual-metal atomically dispersed Fe,Mn/N-C catalyst as model object, we unravel that the O
reduction preferentially takes place on Fe
in the FeN
/C system with intermediate spin state which possesses one e
electron (t
4e
1) readily penetrating the antibonding π-orbital of oxygen. Both magnetic measurements and theoretical calculation reveal that the adjacent atomically dispersed Mn-N moieties can effectively activate the Fe
sites by both spin-state transition and electronic modulation, rendering the excellent ORR performances of Fe,Mn/N-C in both alkaline and acidic media (halfwave positionals are 0.928 V in 0.1 M KOH, and 0.804 V in 0.1 M HClO
), and good durability, which outperforms and has almost the same activity of commercial Pt/C, respectively. In addition, it presents a superior power density of 160.8 mW cm
and long-term durability in reversible zinc-air batteries. The work brings new insight into the oxygen reduction reaction process on the metal-nitrogen-carbon active sites, undoubtedly leading the exploration towards high effective low-cost non-precious catalysts.
The advancement of a naturally rich and effective bifunctional substance for hydrogen and oxygen evolution reaction is crucial to enhance hydrogen fuel production efficiency via the electrolysis ...process. Herein, facile and scalable hydrothermal synthesis of bifunctional electrocatalyst of polyoxometalate anchored zinc cobalt sulfide nanowire on Ni‐foam (NF) for overall water splitting is reported for the first time. The electrochemical analysis of POM@ZnCoS/NF displays significantly low HER and OER overpotentials of 170/337 and 200/300 mV to attain a current density of 10/40 and 20/50 mA cm−2, respectively, demonstrating the notable performance of POM@ZnCoS/NF toward H2 and O2 evolution reaction in alkaline medium. Additionally, the electrolyzer consisting of the POM@ZnCoS/NF anode and cathode shows an appealing potential of 1.56 V to deliver 10 mA cm−2 current density for overall water splitting. The high electrocatalytic activity of the POM@ZnCoS/NF is attributed to modulation of the electronic and chemical properties, increment of the electroactive sites and electrochemically active surface area of the zinc cobalt sulfide nanowires due to the anchorage of polyoxometalate nanoparticles. These results demonstrate the advantage of the polyoxometalate incorporation strategy for the design of cost‐effective and highly competent bifunctional catalysts for complete water splitting.
The present investigation demonstrates a facile route for the fabrication of POM@ZnCoS nanowires for electrocatalytic water splitting via a hydrothermal process. Impressively, POM@ZnCoS nanowires deliver outstanding electrocatalytic behavior with a large number of electroactive sites, very low overpotential, and high durability for the overall water splitting process.
Lithium‐rich layered oxides with the capability to realize extraordinary capacity through anodic redox as well as classical cationic redox have spurred extensive attention. However, the ...oxygen‐involving process inevitably leads to instability of the oxygen framework and ultimately lattice oxygen release from the surface, which incurs capacity decline, voltage fading, and poor kinetics. Herein, it is identified that this predicament can be diminished by constructing a spinel Li4Mn5O12 coating, which is inherently stable in the lattice framework to prevent oxygen release of the lithium‐rich layered oxides at the deep delithiated state. The controlled KMnO4 oxidation strategy ensures uniform and integrated encapsulation of Li4Mn5O12 with structural compatibility to the layered core. With this layer suppressing oxygen release, the related phase transformation and catalytic side reaction that preferentially start from the surface are consequently hindered, as evidenced by detailed structural evolution during Li+ extraction/insertion. The heterostructure cathode exhibits highly competitive energy‐storage properties including capacity retention of 83.1% after 300 cycles at 0.2 C, good voltage stability, and favorable kinetics. These results highlight the essentiality of oxygen framework stability and effectiveness of this spinel Li4Mn5O12 coating strategy in stabilizing the surface of lithium‐rich layered oxides against lattice oxygen escaping for designing high‐performance cathode materials for high‐energy‐density lithium‐ion batteries.
A heterostructured spinel Li4Mn5O12 encapulated lithium‐rich layered oxide cathode is designed by the controlled KMnO4 oxidiation strategy. Spinel Li4Mn5O12 is chosen due to its lattice stability against oxygen release as well as a 3D lithium diffusion framework with minimal Jahn–Teller distortion. Such uniform coating can suppress lattice oxygen release, associated phase transformation, and catalytic side reactions, consequently ensuring improved electrochemical performance.
The development of high‐voltage LiCoO2 is essential for achieving lithium‐ion batteries with high volumetric energy density, however, it faces a great deal of challenges owing to the materials, ...structure and interfacial instability issues. In this work, a strategy is developed, through heat annealing a precoated surface layer to in situ form a high‐voltage‐stable surface coating layer, which is demonstrated to be highly effective to improve the high‐voltage performance of LiCoO2. It is discovered that LiCoO2 reacts with Li1.5Al0.5Ti1.5(PO4)3 (LATP) at 700 °C to form exclusively spinel phases in addition to Li3PO4, which are structurally coherent to the layered lattice of LiCoO2. The heat annealing of the precoated thin layer of LATP enables the formation of a high‐quality surface layer. Spinel phases possess high‐voltage‐stable structures with much weaker oxidizing ability of lattice oxygen than layered structure. In addition, the Li3PO4 is a good lithium‐ion conductor with excellent chemical stability at high voltages. All these benefits contribute to the construction of a uniform and conformal high‐voltage‐stable surface layer with favorable lithium conducting kinetics at the LiCoO2 surface. The modified LiCoO2 shows excellent 4.6 V high‐voltage cycle performance at both room temperature and 45 °C. The thermal stability is greatly enhanced as well.
In situ construction of a high‐voltage‐stable surface coating layer on the LiCoO2 surface is achieved by heat annealing the precoated Li1.5Al0.5Ti1.5(PO4)3 surface layer. The surface‐modified LiCoO2 shows superior 4.6 V high‐voltage cycle performances at both room temperature and 45 °C. The thermal stability of the modified sample is enhanced as well.
Production of ammonia is currently realized by the Haber-Bosch process, while electrochemical N
fixation under ambient conditions is recognized as a promising green substitution in the near future. A ...lack of efficient electrocatalysts remains the primary hurdle for the initiation of potential electrocatalytic synthesis of ammonia. For cheaper metals, such as copper, limited progress has been made to date. In this work, we boost the N
reduction reaction catalytic activity of Cu nanoparticles, which originally exhibited negligible N
reduction reaction activity, via a local electron depletion effect. The electron-deficient Cu nanoparticles are brought in a Schottky rectifying contact with a polyimide support which retards the hydrogen evolution reaction process in basic electrolytes and facilitates the electrochemical N
reduction reaction process under ambient aqueous conditions. This strategy of inducing electron deficiency provides new insight into the rational design of inexpensive N
reduction reaction catalysts with high selectivity and activity.
The paper develops a needs–affordances–features (NAF) perspective on social media use which posits that individuals’ psychological needs motivate their use of social media applications to the extent ...to which these applications provide affordances that satisfy these needs. Our theoretical development builds upon two psychological theories, namely self-determination and psychological ownership, to identify five psychological needs (needs for autonomy, relatedness, competence, having a place, and self-identity), that we posit are particularly pertinent to social media use. According to NAF, these psychological needs will motivate use of those social media applications that provide salient affordances to fulfill these needs. We identify such affordances through a comprehensive review of the literature and of social media applications and put forth propositions that map the affordances to the psychological needs that they fulfill. Our theory development generates important implications. First, it has implications for social media research in that it provides an overarching comprehensive framework for the affordances of social media as a whole and the related psychological needs that motivate their use. Future studies can leverage NAF to identify psychological needs motivating the use of specific social media sites based on the affordances the sites provide, and design science research can leverage NAF in the design and bundling of specific social media features to engage users. Second, it has implications for technology acceptance research in that NAF can enrich existing models by opening up the mechanisms through which psychological needs influence user perceptions of social media and their use patterns and behaviors. Finally, NAF provides a new lens and common vocabulary for future studies, which we hope can stimulate cumulative research endeavors to develop a comprehensive framework of information systems affordances in general and the psychological needs that information systems satisfy.
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