Near Neutral pH Redox Flow Battery with Low Permeability and Long‐Lifetime Phosphonated Viologen Active Species

A highly stable phosphonate‐functionalized viologen is introduced as the redox‐active material in a negative potential electrolyte for aqueous redox flow batteries (ARFBs) operating at nearly neutral pH. The solubility is 1.23 m and the reduction potential is the lowest of any substituted viologen utilized in a flow battery, reaching ?0.462 V versus SHE at pH = 9. The negative charges in both the oxidized and the reduced states of 1,1′‐bis(3‐phosphonopropyl)‐[4,4′‐bipyridine]‐1,1′‐diium dibromide ( BPP?Vi ) effect low permeability in cation exchange membranes and suppress a bimolecular mechanism of viologen decomposition. A flow battery pairing BPP?Vi with a ferrocyanide‐based positive potential electrolyte across an inexpensive, non‐fluorinated cation exchange membrane at pH = 9 exhibits an open‐circuit voltage of 0.9 V and a capacity fade rate of 0.016% per day or 0.00069% per cycle. Overcharging leads to viologen decomposition, causing irreversible capacity fade. This work introduces extremely stable, extremely low‐permeating and low reduction potential redox active materials into near neutral ARFBs.     

Spontaneous Exciton Dissociation at Organic Semiconductor Interfaces Facilitated by the Orientation of the Delocalized Electron–Hole Wavefunction

In organic semiconductors, optical excitation does not necessarily produce free carriers. Very often, electron and hole are bound together to form an exciton. Releasing free carriers from the exciton is essential for the functioning of photovoltaics and optoelectronic devices, but it is a bottleneck process because of the high exciton binding energy. Inefficient exciton dissociation can limit the efficiency of organic photovoltaics. Here, nanoscale features that can allow the free carrier generation to occur spontaneously despite being an energy uphill process are determined. Specifically, by comparing the dissociation dynamics of the charge transfer (CT) exciton at two donor–acceptor interfaces, it is found that the relative orientation of the electron and hole wavefunction within a CT exciton plays an important role in determining whether the CT exciton will decompose into the higher energy free electron–hole pair or relax to the lower energy tightly‐bound CT exciton. The concept of the entropic driving force is combined with the structural anisotropy of typical organic crystals to devise a framework that can describe how the orientation of the delocalized electronic wavefunction can be manipulated to favor the energy‐uphill spontaneous dissociation of CT excitons over the energy‐downhill CT exciton cooling.     

Perovskite Solar Cells go Outdoors: Field Testing and Temperature Effects on Energy Yield

Perovskite solar cells (PSC) have shown that under laboratory conditions they can compete with established photovoltaic technologies. However, controlled laboratory measurements usually performed do not fully resemble operational conditions and field testing outdoors, with day‐night cycles, changing irradiance and temperature. In this contribution, the performance of PSCs in the rooftop field test, exposed to real weather conditions is evaluated. The 1 cm² single‐junction devices, with an initial average power conversion efficiency of 18.5% are tracked outdoors in maximum power point over several weeks. In parallel, irradiance and air temperature are recorded, allowing us to correlate outside factors with generated power. To get more insight into outdoor device performance, a comprehensive set of laboratory measurements under different light intensities (10% to 120% of AM1.5) and temperatures is performed. From these results, a low power temperature coefficient of ?0.17% K^?1 is extracted in the temperature range between 25 and 85 °C. By incorporating these temperature‐ and light‐dependent PV parameters into the energy yield model, it is possible to correctly predict the generated energy of the devices, thus validating the energy yield model. In addition, degradation of the tested devices can be tracked precisely from the difference between measured and modelled power.     

Indoor Thin‐Film Photovoltaics: Progress and Challenges

Energy generation and consumption have always been an important component of social development. Interests in this field are beginning to shift to indoor photovoltaics (IPV) which can serve as power sources under low light conditions to meet the energy needs of rapidly growing fields, such as intelligence gathering and information processing which usually operate via the Internet‐of‐things (IoT). Since the power requirements for this purpose continue to decrease, IPV systems under low light may facilitate the realization of self‐powered high‐tech electronic devices connected through the IoT. This review discusses and compares the characteristics of different types of IPV devices such as those based on silicon, dye, III‐V semiconductors, organic compounds, and halide perovskites. Among them, specific attention is paid to perovskite photovoltaics which may potentially become a high performing IPV system due to the fascinating photophysics of the halide perovskite active layer. The limitations of such indoor application as they relate to the toxicity, stability, and electronic structure of halide perovskites are also discussed. Finally, strategies which could produce highly functional, nontoxic, and stable perovskite photovoltaics devices for indoor applications are proposed.     

PVP Treatment Induced Gradient Oxygen Doping in In2S3 Nanosheet to Boost Solar Water Oxidation of WO3 Nanoarray Photoanode

The photoelectrochemical performance of the WO₃ photoanode is limited by the severe charge recombination in the bulk phase and at the WO₃/electrolyte interface. Herein, In₂S₃ nanosheets are integrated onto the surface of the WO₃ nanowall array photoanode, followed by a facile polyvinylpyrrolidone (PVP) solution treatment. The PVP treatment results in sulfur vacancies and a gradient oxygen doping into In₂S₃ from surface to interior, which induces the formation of a gradient energy band distribution. The gradient band structured In₂S₃ and type II band alignment at the WO₃/In₂S₃ interface simultaneously create a channel that favors photogenerated electrons to migrate from the surface to the conductive substrate, thereby suppressing bulk carrier recombination. Meanwhile, the sulfur vacancies and oxygen doping contribute to increased charge carrier concentration, prolonged carrier lifetime, more active sites, and small interfacial transfer impedance. As a consequence, the PVP treated WO₃/In₂S₃ heterostructure photoanode exhibits a significantly enhanced photocurrent of 1.61 mA cm^?2 at 1.23 V versus reversible hydrogen electrode (RHE) and negative onset potential of 0.02 V versus RHE.     

Accelerating Atomic Catalyst Discovery by Theoretical Calculations‐Machine Learning Strategy

Atomic catalysts (AC) are emerging as a highly attractive research topic, especially in sustainable energy fields. Lack of a full picture of the hydrogen evolution reaction (HER) impedes the future development of potential electrocatalysts. In this work, the systematic investigation of the HER process in graphdyine (GDY) based AC is presented in terms of the adsorption energies, adsorption trend, electronic structures, reaction pathway, and active sites. This comprehensive work innovatively reveals GDY based AC for HER covering all the transition metals (TM) and lanthanide (Ln) metals, enabling the screening of potential catalysts. The density functional theory (DFT) calculations carefully explore the HER performance beyond the comparison of sole H adsorption. Therefore, the screened catalysts candidates not only match with experimental results but also provide significant references for novel catalysts. Moreover, the machine learning (ML) technique bag‐tree approach is innovatively utilized based on the fuzzy model for data separation and converse prediction of the HER performance, which indicates a similar result to the theoretical calculations. From two independent theoretical perspectives (DFT and ML), this work proposes pivotal guidelines for experimental catalyst design and synthesis. The proposed advanced research strategy shows great potential as a general approach in other energy‐related areas.     

New Lithium Salt Forms Interphases Suppressing Both Li Dendrite and Polysulfide Shuttling

Lithium–sulfur batteries (LSBs) are considered promising candidates for the next‐generation energy‐storage systems due to their high theoretical capacity and prevalent abundance of sulfur. Their reversible operation, however, encounters challenges from both the anode, where dendritic and dead Li‐metal form, and the cathode, where polysulfides dissolve and become parasitic shuttles. Both issues arise from the imperfection of interphases between electrolyte and electrode. Herein, a new lithium salt based on an imide anion with fluorination and unsaturation in its structure is reported, whose interphasial chemistries resolve these issues simultaneously. Lithium 1, 1, 2, 2, 3, 3‐hexafluoropropane‐1, 3‐disulfonimide (LiHFDF) forms highly fluorinated interphases at both anode and cathode surfaces, which effectively suppress formation of Li‐dendrites and dissolution/shuttling of polysulfides, and significantly improves the electrochemical reversibility of LSBs. In a broader context, this new Li salt offers a new perspective for diversified beyond Li‐ion chemistries that rely on a Li‐metal anode and active cathode materials.     

Improved power generation using nitrogen-doped 3D graphite foam anodes in microbial fuel cells

Bioprocess and Biosystems Engineering - The properties of the anode material and structure are critical to the microbial growth and interfacial electron transfer between the biofilm and the anode....     

Industrial attributes of β-glucanase produced by Bacillus sp. CSB55 and its potential application as bio-industrial catalyst

Bioprocess and Biosystems Engineering - The β-glucanase produced from Bacillus sp. CSB55 not only depicts the potent industrial characteristics but also relates as bio-industrial catalyst...