ACS Applied Energy Materials最新文献

BiVO₄ is recognized as a promising water-splitting photoanode candidate; however, the inherent properties of short carrier diffusion length, poor electron mobility, and slow surface reaction still impede its application. In response, an incorporated BiVO₄-based photoelectrode has been designed by oxygen vacancy (O_v) fabrication and organometallic complexes decoration. The O_v produced by photoassisted self-reduction dramatically improves the carrier density and conductivity of BiVO₄ and restrains the photogenerated electron–hole recombination. Furthermore, the organometallic complex coating constructed by tannic acid (TA) and single metal (Fe, Co, or Ni) ions plays a positive role in increasing the electrochemically active surface area and accelerating the reaction kinetics. Particularly, the TA-Co decoration can be treated as both a hole transfer and cocatalyst layer. It can quickly extract carriers to reach the electrode surface, simultaneously reduce interface charge transfer resistance, and provide plentiful active sites for the oxygen evolution reaction (OER). The results show that the photocurrent density of the O_V-BiVO₄/TA-Co photoanode attains 3.8 mA cm^–2 at 1.23 V vs RHE, 5.28 times enhanced than that of bare BiVO₄. It also displays good photocorrosion resistance and stability. This work offers a specific path to design the highly active composite photoanode and enables efficient extraction and utilization of photogenerated holes to optimize PEC water-splitting performance.

A comparative study of Bi-doped Si-rich silicide phases, Mg₂Si_0.8Sn_0.2 and Mg₂Si, is reported, investigating in parallel two different synthetic routes: the solid-state reaction (SSR) and mechanical alloying (MA). Both synthetic routes produce the desired silicide phases. However, powder XRD Rietveld refinements reveal appreciable Mg and Sn losses for the SSR-developed Mg₂Si_0.8Sn₂, while EDS measurements also confirm Sn losses together with a decrease in the Bi content. This has a strong impact in electrical transport properties, indicating a severe electron doping deficiency. In contrast, the EDS results for MA-based phases are in a good agreement with the nominal values, indicating an effective Bi doping. Moreover, considering the Rietveld refinement results and SEM analysis, notable changes in the content of Mg interstitial atoms at the 4b crystallographic site seem to be correlated with the microstructure features of the two MA compounds. Electrical conductivity and Seebeck coefficient measurements confirm the aforementioned results. In addition, a small reduction in lattice thermal conductivity is observed for the two MA systems due to the nanostructuring effect. At 773 K, ZT values of 0.85 and 0.6 are exhibited for Mg₂Si_0.8Sn_0.2 and Mg₂Si, respectively. MA is proven to be an advantageous route for the development of Si-rich phases since it provides a better control of doping and higher precision of produced stoichiometric compositions, while in parallel it is a straightforward and scalable method. The replacement of commercial Si by two types of recycled Si-kerf is also attempted here. The kerf-based materials exhibit small reductions in ZT, giving prominence to the efforts to utilize more effectively recyclable Si.

A comparative study of Bi-doped Si-rich silicide phases, Mg₂Si_0.8Sn_0.2 and Mg₂Si, is reported, investigating in parallel two different synthetic routes: the solid-state reaction (SSR) and mechanical alloying (MA). Both synthetic routes produce the desired silicide phases. However, powder XRD Rietveld refinements reveal appreciable Mg and Sn losses for the SSR-developed Mg₂Si_0.8Sn₂, while EDS measurements also confirm Sn losses together with a decrease in the Bi content. This has a strong impact in electrical transport properties, indicating a severe electron doping deficiency. In contrast, the EDS results for MA-based phases are in a good agreement with the nominal values, indicating an effective Bi doping. Moreover, considering the Rietveld refinement results and SEM analysis, notable changes in the content of Mg interstitial atoms at the 4b crystallographic site seem to be correlated with the microstructure features of the two MA compounds. Electrical conductivity and Seebeck coefficient measurements confirm the aforementioned results. In addition, a small reduction in lattice thermal conductivity is observed for the two MA systems due to the nanostructuring effect. At 773 K, ZT values of 0.85 and 0.6 are exhibited for Mg₂Si_0.8Sn_0.2 and Mg₂Si, respectively. MA is proven to be an advantageous route for the development of Si-rich phases since it provides a better control of doping and higher precision of produced stoichiometric compositions, while in parallel it is a straightforward and scalable method. The replacement of commercial Si by two types of recycled Si-kerf is also attempted here. The kerf-based materials exhibit small reductions in ZT, giving prominence to the efforts to utilize more effectively recyclable Si.

Although silicon clathrates were discovered about 60 years ago, there has been little research on diverse applications of such materials beyond thermoelectrics. With a direct bandgap of about 1.7 eV and given the advantages of the silicon element such as abundance, nontoxicity and stability, silicon clathrates hold potential for use in photovoltaics and optoelectronics. Additionally, due to their unique cage structure that can store and release sodium atoms with minimal lattice parameter changes, they are promising for battery applications. However, issues like nonhomogeneity, defects, and poor density in clathrate films have hindered such applications. We provide in this work substantial pathways to mitigate such issues with the use of SF₆ etching and thermal press annealing, enabling an improvement of the optoelectronic properties, by a factor of 7 as observed by the surface photovoltage technique. The photovoltage response of above 200 mV at 0.2 sun being above key photovoltaic thin film absorbers such as CIGS and rivaling III–V semiconductors such as GaAs.

Double half-Heusler (DHH) alloys (XY_0.5Y′_0.5Z) stabilized by mixing two unstable HHs (XYZ and XY′Z) have been the subject of extensive research as an alternative to HHs for high-temperature thermoelectric applications because of the former’s low lattice thermal conductivity. In this work, using a combination of density functional theory (DFT)-based calculations and semiclassical Boltzmann transport theory, we elucidate the role of hierarchical bonding, reduction of electronegativity of X, and chemical pressure induced by variation in its atomic size on the electronic properties, transport, and thermoelectric properties, of a family of DHH compounds, namely, XFe_0.5Ni_0.5Sb (where X = Ti, Zr, and Hf). Compared to the parent compounds, we observe a larger variation in the nature of the bonds in the DHH lattice that aids in the reduction of their lattice thermal conductivity. Our calculations show that electronegativity in the X element and chemical pressure influence the band convergence observed in the conduction band of these materials in a reverse way. While reduction of electronegativity favors band convergence, tensile strain induced in the lattice due to the larger size of X is detrimental for the same. However, electronegativity has a much stronger effect. We observe that HfFe_0.5Ni_0.5Sb, which shows the largest band convergence, has the highest value of zT for n-type charge carriers among the three materials considered in our work. Moreover, hole-doped (p-type) HfFe_0.5Ni_0.5Sb also exhibits zT > 1. Therefore, we envisage that HfFe_0.5Ni_0.5Sb can be a good candidate for both the n and p legs of a thermoelectric device.

High Pt-load catalysts can be used to prepare thin catalytic layers and high-energy-density proton-exchange-membrane fuel cell cathodes for practical applications. However, because high Pt loads agglomerate Pt nanoparticles on carrier surfaces, the batch preparation of high Pt-load catalysts possessing both high activity and high Pt nanoparticle dispersibility is important for practical applications. In this study, high Pt-load Pt/C catalysts were prepared using a platinum nitrate precursor and the high specific surface area Ketjenblack EC600JD carbon carrier via impregnation and liquid-phase hydrogenation reduction. In the catalyst, the average Pt nanoparticle size was 2.30 nm. The electrochemically active surface area of the Pt/C_EC600JD catalyst was 63.91 m² g_Pt^–1, and its mass activity (MA) was 0.35 A mg_Pt^–1 at 0.9 V (versus a reversible hydrogen electrode), which is 1.4 times that of commercial 50% Pt/C_TKK, as measured using a rotating disk electrode. After 20 000 accelerated durability test cycles, the MA of the Pt/C_EC600JD catalyst was 1.7 times that of 50% Pt/C_TKK under the same experimental conditions. The catalyst synthesized using platinum nitrate and EC600JD showed excellent activity and can be used for practical electrocatalytic applications.

By using the ab initio computational methods, this study delves into the feasibility of utilizing graphene–polythiophene (G/PTh) nanocomposites as electrode materials for magnesium-ion (Mg-ion) batteries. The research employs the DMol³ and CASTEP modules within Materials Studio software to systematically analyze the electronic and structural characteristics of G/PTh nanocomposites, shedding light on their potential to enhance energy storage in Mg-ion batteries. The investigation encompasses an in-depth exploration of the interaction between Mg adatoms and the nanocomposites, focusing on the electronic properties, specific capacity, Mg adatom diffusion kinetics, structural and thermal stability, and the underlying mechanisms that govern energy storage. The loading of Mg atoms onto the G/PTh nanocomposite yields a notable maximum specific capacity of 815 mAh/g, indicative of weak adsorption energy (−1.51 eV) and highlighting the potential of the resulting battery as an efficient energy storage device. The nanocomposite exhibits a remarkably low Mg diffusion barrier of 5 meV, facilitating a rapid Mg ions diffusion across its surface. A bandgap of 0.019 eV suggests the promising potential of G/PTh nanocomposites as suitable electrode materials for Mg-ion batteries.

Organic materials offer many advantages as electrodes for lithium-ion batteries (LIBs), including environmental friendliness, flexibility in design, and lightweight. Herein, we demonstrate the successful design and fabrication of pyrene-tethered telluroviologen (Py₂TeV)/single-walled carbon nanotubes (SWCNTs) composite (denoted as Py₂TeV/SWCNTs), in which the Py₂TeV is stably adsorbed onto SWCNTs via π–π interactions. The conjunction of Py₂TeV/SWCNTs effectively suppresses the solubility and improves the stability of the organic materials, thus endowing Py₂TeV/SWCNTs with excellent electronic properties, as compared to the pyrene-tethered parent viologen Py₂V/SWCNTs mixture. When examined as electrode materials for LIBs, the Py₂TeV/SWCNTs display superior electrochemical performance, displaying an initial capacity of 68.5 mAh g^–1 and a long-life cycling performance up to 23 mAh g^–1 after 500 cycles. Due to the characteristic electrochemical properties of Py₂TeV/SWCNTs, they can be used as both cathode and anode electrodes to fabricate all-organic symmetrical LIBs, which show a reversible capacity (27.6 mAh g^–1) after 100 cycles, indicating their potential for the exploration of organic LIBs in the future.

Separator membranes with thermal regulation properties have been developed for battery systems by the addition of phase change material (PCM) microspheres within the polymer separator. Separator membranes based on PCM microspheres (acrylic core–shell particle) and polymer (poly(vinylidene fluoride-co-hexafluoropropylene)), PVDF-HFP, composites were obtained by thermally induced phase separation (TIPS) with different amounts of PCM microspheres (4, 8, and 16 wt %). It is demonstrated that PCM content impacts the morphology of the separator membrane, leading to a decrease in the degree of porosity from 76 to 47%, the β-phase content from 86 to 78%, and the degree of crystallinity from 22 to 13%, with increasing PCM content, leading to variations in electrolyte uptake and electrochemical characteristics of the membranes. Li/C-LiFePO₄ half-cells were produced, and the best cycling behavior was achieved for the membrane with 16 wt % of PCM microspheres, showing 87 mAh.g^–1 after 200 cycles and 2C-rate without capacity fade. Consequently, this work demonstrates a separator membrane with PCM materials with low thermal shrinkage and consequently robust mechanical characteristics, showing thermal regulation properties that can be used in the next generation of safer lithium-ion batteries.

The commercialization of silicon anodes requires polymer binders that are both mechanically robust and electrochemically stable in order to ensure that they can accommodate the volume expansion experienced during cycling. In this study, we examine the use of both low and high molecular weight (MW) polyacrylic acids (PAAs), and sodium polyacrylates (Na-PAAs), at different degrees of partial neutralization, as a possible binder candidate for use in silicon graphite anodes. High MW PAAs were found to have stable capacity retentions of 672 mAh g^-1 for over 100 cycles, whereas with the low MW PAAs the capacity was found to already have declined to 373 mAh g^-1 after the first 30 cycles. Furthermore, the partial neutralization of Na-PAA binder system was found to provide superior cycling performances, as compared to non-neutralized or fully neutralized PAA systems. The high MW and partially neutralized PAAs were also found to provide the electrode coatings with higher cohesion strengths, which allow for the electrodes' microstructure to be more effectively maintained over several cycles. Overall, these findings suggest that partially neutralized and higher MW PAAs are the more suitable polymer binder candidates for use within silicon-graphite anodes.