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This article reviews synthesis strategies for the generation of oxygen vacancies in spinel and perovskite electrodes and discusses the consequences and outlook for supercapacitors.

Investigating photoelectrode interfaces is challenging due to complex charge carrier pathways, and photodegradation aggravates this difficulty because interfacial properties are significantly alter...

Metal nanoclusters (NCs) are a recent addition to the family of traditional photosensitizers (e.g., dyes and quantum dots) for TiO2-based photoelectrodes. Despite the resemblance between NC-based a...

The global burden of bone-related diseases is increasing in the aging society; thus, improved bone targeted imaging for their early identification and treatment are needed. In this study, we screened novel peptide ligands for hydroxyapatite, a major inorganic component of teeth and bones, and identified a peptide enabling in vivo bone targeting and real-time fluorescence bone detection. To isolate peptides highly specific for hydroxyapatite, we used negative and positive selection from a randomized 8-mer peptide phage library and identified hydroxyapatite-specific peptides (HA-pep2, HA-pep3, and HA-pep7). Among these three peptides, HA-pep3 showed the highest binding capacity and superior dissociation constant towards hydroxyapatite surfaces over time (~ 88.3% retained on hydroxyapatite after two weeks). Furthermore, HA-pep3 was highly specific for hydroxyapatite compared to other calcium salt-based materials. Using this superior specificity, HA-pep3 showed higher accumulation in skull, spine, and joints in comparison with scrambled control peptide during real-time whole-body imaging. Ex vivo analysis of the major organs and bone from mice demonstrated that the fluorescence intensity in bone was about 3.32 folds higher in the case of HA-pep3 than the one exhibited by the scrambled control peptide. Our study identified a novel approach for targeting ligands for bone specific imaging and can be useful for drug delivery applications.

Metal nanoclusters (NCs) have emerged as feasible alternatives to dyes and quantum dots in light energy conversion applications. Despite the remarkable enhancement in power conversion efficiency (PCE) in recent years and the increase in the number of NCs available as sensitizers, a comprehensive understanding of the various interfacial charge-transfer, transport, and recombination events in NCs is still lacking. This understanding is vital to the establishment of design principles for an efficient photoelectrode that uses NCs. In this work, we carefully design a comparison study of two representative NCs, Au and Ag, based on transient absorption spectroscopy and electrochemical impedance spectroscopy, methods that shed light on the true benefits and limitations of NC sensitizers. Low NC regeneration efficiency is the most critical factor that limits the performance of metal-nanocluster-sensitized solar cells (MCSSCs). The slow regeneration that results from sluggish hole transfer kinetics not only limits photocurrent generation efficiency but also has a profound effect on the stability of MCSSCs. This finding calls for urgent attention to the development of an efficient redox couple that has a great hole-extraction ability and no corrosive nature. This work also reveals different interfacial behaviors of Au and Ag NCs in photoelectrodes, suggesting that utilizing the benefits of both types of NCs simultaneously by cosensitization or using AuAg alloy NCs may be one avenue for further PCE improvement in MCSSCs.

The limited capacity of graphite anodes in high-performance batteries has led to considerable interest in alternative materials in recent years. Due to its high capacity, titanium niobium oxide (TiNb

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The presence of alkali metal ions (AMIs) during the adsorption of thiolated Au nanoclusters (NCs) onto TiO2 plays a critical role in achieving high power conversion efficiency and suppressing anoma...

Despite the successful debut of gold nanoclusters (Au NCs) in solar cell applications, Au NCs, compared to dyes and quantum dots, have several drawbacks, such as lower extinction coefficients. Any modulation of the physical properties of NCs can have a significant influence on the delicate control of absorbance, energy levels, and charge separation, which are essential to ensure high power conversion efficiency. To this end, we systematically alter the optoelectronic structure of Au18(SR)14 by Ag doping and explain its influence on solar cell performance. Our in-depth spectroscopic and electrochemical characterization combined with computational study reveals that the performance-dictating factors respond in different manners to the Ag doping level, and we determine that the best compromise is the incorporation of a single Ag atom into an Au NC. This new insight highlights the unique aspect of NCs—susceptibility to atomic level doping—and helps establish a new design principle for efficient NC-based solar cells.

Nanostructuring of catalytically active materials has been an important research topic to identify robust yet cost-effective electrocatalysts. Despite the many benefits of nanostructured catalysts, their use in practical systems has not yet been fully realized due to their many technical challenges. A great deal of effort has been made to overcome the hurdles of nanomaterials, but we postulate that the solution to these problems may not necessarily result from technology based on nanomaterials. In this work, we demonstrate this by demonstrating a new thermal route that can produce an electrocatalytically active material for the oxygen evolution reaction from its bulk form that has a very low catalytic activity. In our synthesis protocol, the oxidation and subsequent sulfidation of bulk cobalt sulfide (CoSx) are delicately exploited so that its composition and porous structure are manipulated to make bulk CoSx as active as the state-of-the-art IrO2 catalyst. Given the simplicity and mass productivity, this re-engineering strategy based on sulfur/oxygen exchange reactions will pave a new avenue for designing cost-effective, active electrocatalysts. We also anticipate this method to provide an opportunity to reassess the potential of bulk materials for electrocatalysis.

Despite the successful launch of Au nanoclusters (NCs) in light energy conversion applications, the utilization of Ag NCs has been limited by their instability under continuous illumination. The main cause of photoinduced degradation pathways remains elusive. Hence, understanding the underlying mechanism behind the low stability is an urgent task to provide a new impetus for the development of Ag NCs. The slow regeneration of Ag NCs by a redox couple leads to holes in the NCs, which could result in either the photoetching of NCs or the transformation into plasmonic nanoparticles. Transient absorption spectroscopy reveals that Ag NCs coalesce into plasmonic nanoparticles and begin to experience two conflicting effects (plasmonic enhancement and quenching effect) during this in situ transformation. It also discloses that the quenching effect prevails over the plasmonic enhancement, which eventually leads to photocurrent loss under illumination.

For high performance of electrical double layer capacitors (EDLCs), a high specific surface area (SSA) and N-doping level, and small particle size of carbonaceous materials, have been believed to be crucial factors. However, there have been few reports on simultaneous study of the structure-properties relations of carbons and the electrochemical performances of EDLCs. Herein, we report the relationship between the structural properties of carbons, such as the SSA, N-doping, and particle size, and the electrochemical properties of EDLCs by using a series of well-defined carbons. Monodisperse and size-tunable resorcinol-formaldehyde carbon (RFC) spheres were synthesized and activated by hot CO2 treatment to increase the SSA up to 3958 m2/g (RFC_C390 sample). When the specific capacitances of the RFC spheres were plotted in terms of their SSAs, an almost perfect correlation (R2 = 0.99) was observed, which confirmed the linear relationship between the specific capacitance and the SSA. In addition, N-doped melanin C (MC) spheres were synthesized and subsequently activated for N-doping effect. Activated MC (MC_C130), which exhibited similar SSA (2618 m2/g) and size (301 nm) but a different N-doping level (3.1%) compared with those (2793 m2/g, 312 nm, and 1.3%, respectively) of the activated RFC spheres (RFC_C120), displayed higher specific capacitance (288 F/g), capacitance retention (64%), and long term stability over 5000 cycles (93%) compared with those (260 F/g, 58%, and 90%, respectively) of the RFC counterparts. To observe the particle size effect, different sizes (98, 280, and 579 nm) of RFC spheres with similar SSAs (3981, 3958, and 3898 m2/g, respectively) and pore size distributions were prepared, such that the smallest RFC revealed the best EDLC performance in terms of specific capacitance (360 F/g), capacitance retention (70%), and long term stability over 5000 cycles (98%), all of which could be compared with the values reported in the literature. Furthermore, all of the Carbon samples were analyzed by using electrochemical impedance spectroscopy for confirming the structure-properties relations of carbon spheres with the electrochemical performances of EDLCs.

The presence of oxygen functional groups (OFGs) on a carbon surface is a double-edged sword in electric double-layer capacitors (EDLCs) because of their mixed influences on capacitance. Critical problems of common OFGs are greatly decreased electrical conductivity, steric hindrance limiting the migration of ions, and promoted self-discharge via faradaic reactions. To explore a new breakthrough to these long-standing problems, carbon electrodes selectively functionalized with cyclic ether groups (CEGs) are investigated with in-depth spectroscopic and electrochemical analyses. The in-plane CEGs embedded in the graphene matrix are greatly advantageous over conventional out-of-plane OFGs for EDLC performance because they can boost capacitance via pseudocapacitance while substantially minimizing all of the negative effects of traditional OFGs. This study also reveals that preserving the original sp2 carbon network during surface functionalization is crucial to maximizing the benefits of OFGs. These new insights call for the development of elaborate surface engineering strategies that can introduce functionalities with no significant damage to π-conjugation.

Li4Ti5O12 (LTO) has attracted considerable attention in lithium-ion battery (LIB) applications because of its favorable characteristics as an anode material. Despite its promise, the widespread use of LTO is still limited primarily due to its intrinsically poor electric and ionic conductivities and high surface reactivity. To address these issues, we designed polygonal nanoarchitectures composed of various Li–Ti oxide crystal polymorphs by a facile synthesis route. Depending on the pH condition, this synthesis approach yields multi-polymorphed Li–Ti oxides where the interior is dominantly composed of a Li-rich phase and the exterior is a Li-deficient (or Li-free) phase. As one of these variations, a polygonal LTO-rutile TiO2 structure is formed. The rutile TiO2 on the surface of this LTO composite significantly improves the kinetics of Li+ insertion/extraction because the channel along the c-axis in TiO2 provides a Li+ highway due to the significantly low energy barrier for Li+ diffusion. Moreover, the presence of rutile TiO2, which is less reactive with a carbonate-based electrolyte, ensures long-term stability by suppressing the undesirable interfacial reaction on LTO.

Despite the many benefits of hierarchical nanostructures of oxide-based electrode materials for lithium-ion batteries, it remains a challenging task to fully exploit the advantages of such material...

High nickel layered oxides are attractive cathode materials that can achieve high energy density in lithium-ion batteries (LIBs). Many researchers have strived to improve the cycling stability and energy density of LiNiO2 (LNO) through another metal mixing, dopping, or coating method. However, the particle size effect of pure LNO during the charging/discharging system has not been fully understood yet. Many computing research results revealed that smaller-particle materials with highly connective interfaces and reduced diffusion paths exhibit higher rate performance and good cycling stability than bulk counterparts. However, our study revealed that the different particle size of LNO has a very different trend in contrast to the computation results because they overlooked the influence of primary particles. In this study, we focus on the impact of the particle size distribution of spherical cathode material on positive electrodes in LIBs. We designed four different particle sizes of Ni(OH)2 by controlling pH, time, and agitation speed. When the other conditions were the same except for the particle size, we were able to explore how the grain size, Li off-stoichiometry (Li1-zNi1+zO2), and activation energy affect the battery performance. Through size comparison, a better understanding of the influence of particle size distribution was obtained, which would be an important basis to engineer electrodes for higher C-rate capability, higher performance, and better stability during battery cycling.

Lithium-ion batteries (LIBs) become an essential part of many portable devices and even electric vehicles than ever before. Among the various cathode materials, Ni rich layered cathode material has big attention because it has higher specific capacity and energy density. However, at a delithiated state, unstable Ni4+ leads to oxygen release and structural degradation and as a result, irreversible phase transition from R3m to electrochemical inactive Fm3m is observed. So, various strategy is applying to overcome this limitation like three-component system (NCM) or surface coating. However, NCM still cannot solve that problem perfectly and surface coating makes a problem like reducing specific capacity caused by insulating coating material (Al2O3, MnO2...etc) And also, this day, Co free structure of Ni rich cathode material has received more great attention as an alternative to NCM because of its hazardous toxicity and increasing price of Co. At this perspective, many studies have demonstrated Core-Shell or FCG (Full Concentration Gradient) structure can make better structural stability without Co metal than surface coating, which has insulated coating materials. In addition, core shell structure is easier to control the composition than FCG structure. However, in Core-Shell structure, interdiffusion of shell metal to core deteriorate the stability of Core-Shell material, so it needs very delicate heat treatment. And generally, to prevent interdiffusion from traditional core-shell structure, lower synthesis temperature or high valence metal dopant would be needed and that leads lower initial specific capacity or additional doped metal. So, we prevent the Mn interdiffusion by changing valence state of Mn in precursor through simple convection drying process not vacuum drying without decreasing synthesis temperature and additional dopant. Atomic interdiffusion in layered metal oxide structures follows the atomic migration through octahedral and tetrahedral sites. In case of various stated Mn, higher valence state Mn has higher energy barrier to migrate between each Oh and Td sites. Based on this theory, surface Mn rich shell can be oxidized easily under convection oven drying and highly oxidized Mn will be remained better than lower state Mn during high temperature calcination. These more remained Mn in shell can protect the particle surface from electrolyte attack and also higher valence state Mn makes slightly more Ni2+ due to thermodynamic stability and charge balance of Mn on the surface. And that Ni2+ in Li slab (Cation mixing) acts as a pillar to suppress irreversible phase transition of Ni rich materials. Through this surface passivation, phase transition (layered to rock salt ) propagation surface to bulk can be blocked. Furthermore, mechanical pulverization of secondary particle is also prevented because of less permeating electrolyte into bulk structure. Therefore, Li ion diffusion will not be sluggish after cycling as observed by GITT. In addition, more clear Ni rich core assure high specific capacity and faster electrochemical reaction kinetic without severe capacity fading. And also, in Full cell test (using graphite as anode), convection oven dried sample has better structure stability and that means our strategy for core-shell LiNi0.97Mn0.03O2 sample can be good candidate to alternate conventional cathode active material for Lithium ion battery practically. As prepared materials, atomic distribution was observed by EDS and XPS analysis. This study suggests useless of vacuum drying and more cost effective way to prepare Co free Core Shell LiNi0.97Mn0.03O2 cathode material for Lithium Ion Batteries.

Metal oxide semiconductor/chalcogenide quantum dot (QD) heterostructured photoanodes show photocurrent densities >30 mA/cm2 with ZnO, approaching the theoretical limits in photovoltaic (PV) cells. However, comparative performance has not been achieved with TiO2. Here, we applied a TiO2(B) surface passivation layer (SPL) on TiO2/QD (PbS and CdS) and achieved a photocurrent density of 34.59 mA/cm2 under AM 1.5G illumination for PV cells, the highest recorded to date. The SPL improves electron conductivity by increasing the density of surface states, facilitating multiple trapping/detrapping transport, and increasing the coordination number of TiO2 nanoparticles. This, along with impeded electron recombination, led to enhanced collection efficiency, which is a major factor for performance. Furthermore, SPL-treated TiO2/QD photoanodes were successfully exploited in photoelectrochemical water splitting cells, showing an excellent photocurrent density of 14.43 mA/cm2 at 0.82 V versus the Reversible Hydrogen Electrode (RHE). These results suggest a new promising strategy for the development of high-performance photoelectrochemical devices.

Metal oxide semiconductor/chalcogenide quantum dot (QD) heterostructured photoanodes show photocurrent densities >30 mA/cm2 with ZnO, approaching the theoretical limits in photovoltaic (PV) cells. However, comparative performance has not been achieved with TiO2. Here, we applied a TiO2(B) surface passivation layer (SPL) on TiO2/QD (PbS and CdS) and achieved a photocurrent density of 34.59 mA/cm2 under AM 1.5G illumination for PV cells, the highest recorded to date. The SPL improves electron conductivity by increasing the density of surface states, facilitating multiple trapping/detrapping transport, and increasing the coordination number of TiO2 nanoparticles. This, along with impeded electron recombination, led to enhanced collection efficiency, which is a major factor for performance. Furthermore, SPL-treated TiO2/QD photoanodes were successfully exploited in photoelectrochemical water splitting cells, showing an excellent photocurrent density of 14.43 mA/cm2 at 0.82 V versus the Reversible Hydrogen Electrode (RHE). These results suggest a new promising strategy for the development of high-performance photoelectrochemical devices. Funding for open access charge: CRUE-Universitat Jaume I This work was supported by the Korea Center for Artificial Photosynthesis (KCAP) of Sogang University, funded by the Ministry of Science, ICT, and Future Planning (MSIP) through a National Research Foundation of Korea (Grant no. 2009-0093883). This work also was supported by a grant from the Basic Science Research Program through the National Research Foundation (NRF) of Korea funded by the Ministry of Science and ICT (NRF-2019R1A2C1003429) and by the Ministry of Education (NRF-2018R1A6A1A03024231). Also, this work was supported by the Ministerio de Ciencia, Innovacio′n y Universidades of Spain through the project ENE2017–85087-C3-1-R. Therefore, the authors acknowledge and thank the Korean and Spanish governments for technical and financial support. S. D. G.

Many bottom-up nanostructuring approaches have benefitted the research field of electrocatalysis by significantly increasing the catalytic activity of electrocatalysts. In general, however, they require tedious wet chemistry steps and delicate control while managing considerable surface energies. In addition, they often suffer from scalability issues. As part of an effort to address these issues, we developed a simple two-step thermal route to produce a nanostructured electrocatalyst with high catalytic activity from its bulk form. In this work, we demonstrate the preparation of core/shell CoO/CoSx from bulk Co3O4 as a case study. Our novel approach uses a low-temperature thermal treatment under NH3 and a subsequent treatment in a H2S atmosphere, judiciously exploiting the unique features of each reaction atmosphere. Hot NH3 treatment reduces Co3O4 to CoO, during which a significant lattice mismatch between the Co3O4 and CoO fractures crystallites, and the coalescence of oxygen vacancies introduces porosity. Subsequent H2S treatment specifically forms electrocatalytically active CoSx species on the surface of CoO. We explore the use of the resulting nanostructured CoO/CoSx as an alternative to state-of-the-art noble metal catalysts in the triiodide reduction and oxygen evolution reactions, finding that its activity is comparable to those of standard catalysts. Given the simplicity and scalability of this innovative low-temperature reaction concept, we anticipate that the present demonstration will open new avenues for the synthesis of highly active electrocatalysts.

A unique decomposition pathway of urea involving gas evolution was exploited as a way to introduce voids and mesopores into one-dimensional carbon nanofibers. While the conventional carbonization of electrospun polyacrylonitrile (PAN) nanofibers produces microporous and solid carbon nanofibers, adding a simple step involving a urea coating over PAN prior to the carbonization drastically changes the porous structure of the resulting carbon nanofibers. Besides its role as a porogen for the creation of voids and mesopores, urea serves as an additional nitrogen source for the carbon nanofibers, and as a consequence, heavily nitrogen-doped carbon fibers are produced. Compared with conventional carbon nanofibers derived from the pyrolysis of electrospun PAN, hollow carbon nanofibers are superior in lithium-ion battery applications because of their larger specific surface area, higher nitrogen doping, and voids combined with mesopores that are beneficial for lithium-ion (de-)intercalation. Due to its versatility and simplicity, this urea-assisted template-less synthesis strategy paves a new way for the production of various porous carbon nanostructures.

Despite many new advances in supercapacitor material design, few have been adopted for industrial use because of a lack of consideration for industrial requirements. This fact has long been overlooked in academia, but the potential impact of the technical gap between laboratory-scale demonstrations and large-scale applications is considerable. To this end, we performed a proof-of-concept study using vanadium pentoxide (V2O5), one of the most promising supercapacitor electrode materials, to narrow this technical gap. We demonstrated a facile thermal approach in which electrochemically poor bulk V2O5 can be transformed into a highly active electrode material, which can be potentially developed for an economical large-scale production process. Two subsequent thermal treatments of bulk V2O5 under NH3 and H2S gas flow yielded a pseudocapacitive nanocomposite composed of vanadium oxynitride and vanadium sulfide. Superior capacitive performance of the bulk V2O5 in terms of capacitance and stability was achieved by this novel electrode material. In-depth characterization and electrochemical analysis revealed that the underlying reason for this enhancement resulted from a synergistic effect induced by the two-step thermal process. We believe that this successful demonstration of our conceptual approach will be an important stepping stone toward the development of practical material design processes that can meet the rigorous demands of the industry.

Ultrathin and conformal ZnS film grown by atomic layer deposition was employed in quantum dot-sensitized solar cells (QDSSCs) as an interfacial layer (IL) between mesoporous TiO2 photoanode and successive ionic layer adsorption and reaction (SILAR)-grown PbS QDs. ZnS IL provided more nucleation sites compared to a bare TiO2 photoanode, which enhanced PbS QDs loading remarkably. As a result, the optical absorbance and thus photocurrent density considerably increased. The power conversion efficiency of QDSSCs increased from 3.4% to 4% by introducing the ZnS IL. However, the β-recombination model obtained from electrochemical impedance spectroscopy revealed the evolution of charge carrier recombination inside QDs as a consequence of enhanced QD loading, which partly dilutes this benefit.

Few-atom gold nanoclusters (NCs) exhibit molecule-like properties due to a discrete electronic structure driven by the quantum confinement effect. Unlike plasmonic Au particles, these nonplasmonic particles of diameter less than 2 nm, commonly referred to as nanoclusters, possess a distinct excited-state behavior that can offer a new opportunity to employ them as a photosensitizer. Their size-dependent excited-state behavior enables establishing logical designing principles to build up efficient light energy conversion systems. The photodynamics of thiolated Au NCs and efforts to exploit the Au NCs in light energy conversion applications discussed in this Review show new opportunities to utilize them as photosensitizers. Current bottlenecks in implementing thiolated Au NCs in light conversion applications and new strategies and future directions to address these limitations are also discussed.

Infection with dengue virus (DENV) is a serious health issue that causes severe dengue fever and occasionally lethal complications, such as dengue hemorrhagic fever. Therefore, rapid and sensitive DENV detection is important to reduce morbidity and mortality. Here, we screened dengue NS1-specific affibodies and developed highly stable anti-NS1 affibody-functionalized AuNPs to improve the detection sensitivity of the NS1 antigen in ELISA. First, we screened NS1 antigen-specific affibody molecules (ZNS112, ZNS116, and ZNS146) from an affibody phage library. The affibodies were then expressed and purified from Escherichia coli. Among them, the ZNS112 affibody showed the highest equilibrium binding constant (Kd) of 1 μM and was sufficiently stable at high temperatures. This affibody was functionalized on AuNPs measuring 20 nm in diameter, which were used as carriers to achieve amplification of the signal in ELISA. The developed anti-NS1 affibody-functionalized AuNPs ((ZNS112)2–AuNP) showed good properties, such as easy synthesis, a high number of affibody conjugations on the AuNPs, and excellent stability under harsh conditions with high salt concentrations and temperature. In addition, this nanoparticle-based enhanced ELISA resulted in a 14.2-fold signal amplification performance for dengue NS1 detection in comparison with the affibody-based ELISA. This novel and sensitive method using (ZNS112)2–AuNPs may have applications in the detection of DENV in infected patients at an early stage and for the detection of other pathogens in clinical diagnostics.

Nanostructuring is an essential step in synthesizing highly active electrocatalysts. Unfortunately, it has not been widely adopted in the electrodes of commercial electrolyzers because of difficulties associated with scalability and process complexity. As a remedy to this long-standing problem, we demonstrate a facile thermal route to transform poor oxide electrocatalysts into highly active ones by utilizing hot H2S gas as a dual functional agent. Using bulk cobalt oxide as a model system, we reveal that H2S that would otherwise be stable up to 1000 °C can be catalytically decomposed on the surface of Co3O4 into H2 and sulfur species at a moderately high temperature. The produced H2 and sulfur react with Co3O4 and transform it into nanostructured Co3O4/CoO@CoSx particles that are highly active towards the oxygen evolution reaction. The optimum sample can be produced after only 10 min of H2S treatment, highlighting the simplicity and scalability of our process.

The electrocatalytic activity of carbon materials for triiodide (I3–) reduction has spurred the development of low-cost electrocatalysts as an alternative to platinum in dye-sensitized solar cells. While many catalytic aspects of nitrogen-doped carbons have been unveiled in recent years, not all underlying factors that dictate their electrocatalytic activity have been fully considered; the current understanding of the electrocatalytic activity of nitrogen-doped carbons is limited. In addition, the synergistic effect of metal nanoparticles embedded in nitrogen-doped carbon, which was recently demonstrated as a facile way to boost the electrocatalytic activity of carbon, remains elusive. This work sheds light on these unknown aspects of carbon’s electrocatalytic activity by carrying out a systematic investigation of nitrogen-doped carbon with incorporated cobalt nanoparticles. Furthermore, the generally accepted mechanism of the I3– reduction reaction (IRR) is re-evaluated in this work with the aid of densi...

A new nanoarchitecture of cobalt sulfide (CoSx) is designed by exploiting a Prussian blue analogue. Depending on the sulfidation temperatures, CoSx materials with different compositions and morphologies are obtained. This investigation of the composition-dependent electrocatalytic activity of CoSx for triiodide reduction reaction (IRR) reveals that sulfur-deficient CoSx is more active than sulfur-rich CoSx. When utilized in dye-sensitized solar cells (DSSCs), sulfur-deficient CoSx with a hollow nanocube morphology outperforms platinum (Pt), showing great promise as a Pt alternative. This composition dependency on IRR is attributed to different surface characteristics and electrical properties that vary with CoSx composition. This work highlights the importance of understanding the surface properties of sulfide-based electrocatalysts that are intimately dictated by their compositions as part of a new design principle for a highly active electrocatalyst.

One way to revolutionize solar energy production and expand it to a large scale is to reduce the manufacturing cost and complexity of the fabrication process. The ability to make solar cells on the surface of any shape would further transform this technology. Quantum dot-sensitized solar cells (QDSSCs) are an ideal candidate to push solar cell technology in this direction. In this regard, making a paint that can be applied by a paint brush to any transparent conductive surface to turn it into the photoanode of QDSSCs is the ultimate goal. We herein demonstrate the feasibility of one-coat fabrication of QDSSCs from a lead sulfide (PbS)-based solar paint. This is possible because of its unique ability to regenerate after oxidation occurred during heat treatment in air. Hence, the whole fabrication process can be carried out in air unlike a first-generation solar paint based on cadmium sulfide (CdS) and cadmium selenide (CdSe). Two solar paints using a commercially available titanium dioxide (TiO2) and a p-t...

Macroporous titanium dioxide (TiO2) layer was formed through selective etching of silica (SiO2) microspheres incorporated in TiO2/SiO2 composite layer, resulting in a significant increase in the photovoltaic performance of PbS quantum-dot-sensitized solar cells (QDSSCs). Strategic incorporation of macroporous TiO2 layer on top of a mesoporous layer improved the light absorption characteristics, which is concurrently attributed to light scattering behaviour of macropores and increased loading of quantum dots (QDs) via successive ionic layer adsorption and reaction process. Thereby, a direct increase in the photocurrent density of PbS-QDSSC was ensued. Open-circuit voltage decay analysis combined with in-depth electrochemical impedance spectroscopy revealed a significant improvement in the electron life time and recombination resistance of QDSSC which was credited to the barrier effect of more uniformly loaded PbS QDs inside macroporous TiO2 photoanode.

Intrinsic low stability and short excited lifetimes associated with Ag nanoclusters (NCs) are major hurdles that have prevented the full utilization of the many advantages of Ag NCs over their longtime contender, Au NCs, in light energy conversion systems. In this report, we diagnosed the problems of conventional thiolated Ag NCs used for solar cell applications and developed a new synthesis route to form aggregation-induced emission (AIE)-type Ag NCs that can significantly overcome these limitations. A series of Ag(0)/Ag(I)-thiolate core/shell-structured NCs with different core sizes were explored for photoelectrodes, and the nature of the two important interfacial events occurring in Ag NC-sensitized solar cells (photoinduced electron transfer and charge recombination) were unveiled by in-depth spectroscopic and electrochemical analyses. This work reveals that the subtle interplay between the light absorbing capability, charge separation dynamics, and charge recombination kinetics in the photoelectrode dictates the solar cell performance. In addition, we demonstrate significant improvement in the photocurrent stability and light conversion efficiency that have not been achieved previously. Our comprehensive understanding of the critical parameters that limit the light conversion efficiency lays a foundation on which new principles for designing Ag NCs for efficient light energy conversion can be built.

The synthesis of a one-dimensional (1D) array of cobalt disulfide (CoS2) integrated on carbon fiber paper (CFP) was used to prepare an efficient CoS2 electrocatalyst for the hydrogen evolution reaction (HER). The combination of benefits from the unique nano-pine-tree morphology of CoS2 and interwoven carbon network in the CFP offers high electrocatalytic activity and durability, which make this newly nanostructured catalyst suitable as an alternative to platinum (Pt). We also demonstrated the generalization of this synthesis approach to various metal disulfide arrays, which make it of interest in nanoarchitecture.