Shape‐ and Size‐Controlled Synthesis of Uniform Anatase TiO2 Nanocuboids Enclosed by Active {100} and {001} Facets

Uniform anatase TiO₂ nanocuboids enclosed by active {100} and {001} facets over a wide size range (60–830 nm in length) with controllable aspect ratios were solvothermally synthesized through hydrolysis of titanium tetraisopropoxide (TTIP) using acetic acid (HAc) as the solvent and the ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF₄]) as the capping agent. The size and aspect ratio of the anatase TiO₂ nanocuboids can be readily adjusted by changing the composition parameters including the contents of [bmim][BF₄], water, and HAc in the quaternary solution system. It was revealed that [bmim][BF₄] played an important role in stabilizing both the {100} and {001} facets of the anatase TiO₂ nanocuboids. On the one hand, [bmim][BF₄] acted as a fluoride source to release F^? ions for stabilizing the {001} facets; on the other hand, the [bmim]⁺ ions acted as effective capping ions to preferentially stabilize the {100} facets. The obtained near‐monodisperse anatase TiO₂ nanocuboids exhibited an interesting self‐assembly behavior during deposition. These single‐crystalline anatase nanocuboids showed extremely high crystalline phase stability, retaining the pure phase of anatase as well as the morphology even after being calcined at 900 °C. Moreover, the anatase nanocuboids exhibited considerably enhanced photocatalytic activity owing the wholly exposed active {100} and {001} facets.     

Refining Energy Levels in ReS2 Nanosheets by Low‐Valent Transition‐Metal Doping for Dual‐Boosted Electrochemical Ammonia/Hydrogen Production

Electrocatalytic nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER) are intriguing approaches to nitrogen fixation and hydrogen production under ambient conditions, given the need to discover efficient and stable catalysts to light up the “green chemistry” future. However, bottlenecks are often found during N₂/H₂O activation, the very first step of NRR/HER, due to energetic electron injection from the surface of electrocatalysts. It is reported that the bottlenecks for both NRR and HER can be tackled by engineering the energy level via low‐valent transition‐metal doping, simultaneously, where rhenium disulfide (ReS₂) is employed as a model platform to prove the concept. The doped low‐valent transition‐metal domains (e.g., Fe, Co, Ni, Cu, Zn) in ReS₂ provide more active sites for N₂/H₂O chemisorption and electron transfer, not only weakening the N?N/O? H bonds for easier dissociation through proton coupling, but also elevating d‐band center toward the Fermi level with more electron energy for N₂/H₂O reduction. As a result, it is found that iron‐doped ReS₂ nanosheets wrapped nitrogen‐doped carbon nanofiber (Fe‐ReS₂@N‐CNF) catalyst exhibits superior electrochemical activity with eightfold higher ammonia production yield of 80.4 µg h^?1 mg^?1_cat., and lower onset overpotential of 146 mV and Tafel slope of 63 mV dec^?1, when comparing with the pristine ReS₂.     

Photoelectrochemical Synthesis of Ammonia with Black Phosphorus

Efficient production of ammonia using environmentally friendly techniques under ambient conditions is crucial to renewable energy storage and industrial applications, and catalysts with new reaction pathways are highly desirable. In this work, black phosphorus (BP) is used as a metal‐free 2D catalyst for the photoelectrochemical (PEC) nitrogen reduction reaction (NRR). The electrode is fabricated by layer‐by‐layer assembly of BP nanosheets on an indium tin oxide substrate. The PEC NRR activity in the N₂ saturated aqueous electrolyte without a sacrificial agent is excellent, as exemplified by an ammonia yield rate of 102.4 µg h^?1 mgcat.^?1 and Faradaic efficiency of 23.3% at ?0.4 V, which are the best among nonmetal catalysts for synthesis of ammonia by photocatalysis and electrocatalysis. Furthermore, the BP electrode shows excellent stability after 6 consecutive cycles. The excellent PEC catalytic properties are attributed to the light excitation enhanced electrocatalytic process and that the external bias promoted photocatalytic process improves ammonia production synergistically. The results not only demonstrate the great potential of BP in PEC catalysis, but also identify a promising technique to produce ammonia under ambient conditions using solar energy and electric energy.     

Engineering Facets and Oxygen Vacancies over Hematite Single Crystal for Intensified Electrocatalytic H2O2 Production

Hydrogen peroxide is a highly valuable chemical, and electrocatalytic oxygen reduction towards H₂O₂ offers an alternative method for safe on‐site applications. Generally, low‐cost hematite (α‐Fe₂O₃) is not recognized as an efficient electrocatalyst because of its inert nature, but it is herein reported that α‐Fe₂O₃ can be endowed with high catalytic activity and selectivity via the engineering of facets and oxygen vacancies. Density‐functional theory (DFT)calculations predict that the {001} facet is intrinsically selective for H₂O₂ production, and that oxygen vacancies can trigger the high activity, providing sites for O₂ adsorption and protonation, stabilizing the *OOH intermediate, and preventing cleavage of the O? O bond. The synthesized oxygen‐defective α‐Fe₂O₃ single crystals with exposed {001} facets achieve high selectivities for H₂O₂ of >90%, >88%, and >95% in weakly acidic, neutral, and alkaline electrolytes, respectively, and the H₂O₂ production rate reaches 454 mmol g^?1_cat h^?1 at 0.1 V versus RHE under alkaline conditions. In an anion exchange membrane fuel cell, a maximum H₂O₂ production of 546.8 mmol L^?1 with a high Faradaic efficiency of 80.5% is achieved. Thus, this work details a low‐cost catalyst feasible for H₂O₂ synthesis, and highlights the feasibility of theoretical catalyst design for practical applications.     

Tuning the Catalytic Preference of Ruthenium Catalysts for Nitrogen Reduction by Atomic Dispersion

Developing cost‐effective, high‐performance nitrogen reduction reaction (NRR) electrocatalysts is required for the production of green and low‐cost ammonia under ambient conditions. Here, a strategy is proposed to adjust the reaction preference of noble metals by tuning the size and local chemical environment of the active sites. This proof‐of‐concept model is realized by single ruthenium atoms distributed in a matrix of graphitic carbon nitride (Ru SAs/g‐C₃N₄). This model is compared, in terms of the NRR activity, to bulk Ru. The as‐synthesized Ru SAs/g‐C₃N₄ exhibits excellent catalytic activity and selectivity with an NH₃ yield rate of 23.0 µg mg_cat^?1 h^?1 and a Faradaic efficiency as high as 8.3% at a low overpotential (0.05 V vs the reversible hydrogen electrode), which is far better than that of the bulk Ru counterpart. Moreover, the Ru SAs/g‐C₃N₄ displays a high stability during five recycling tests and a 12 h potentiostatic test. Density functional theory calculations reveal that compared to bulk Ru surfaces, Ru SAs/g‐C₃N₄ has more facile reaction thermodynamics, and the enhanced NRR performance of Ru SAs/g‐C₃N₄ originates from a tuning of the d‐electron energies from that of the bulk to a single‐atom, causing an up‐shift of the d‐band center toward the Fermi level.     

Highly Porous and Preferentially Oriented {100} Platinum Nanowires and Thin Films

Highly {100} oriented Pt deposits were prepared by electrodeposition from a 10 mM HCl, 100 mM KCl and Na₂PtCl₆.xH₂O electrolyte. The deposits were prepared in the form of thin films and array of nanowires. A qualitative assessment of the proportion of {100} oriented Pt surfaces was obtained through X‐ray diffraction measurements and cyclic voltammetry in 0.5 M H₂SO₄. The effect of the deposition potential, E_dep, temperature of the electrolyte, T_dep, platinum salt concentration [Na₂PtCl₆.xH₂O], and nature of the substrate were investigated. It was shown that the proportion of {100} oriented Pt surfaces reaches a maximum for E_dep = ‐0.35 V vs SCE. Moreover, this proportion increases steadily as T_dep and [Na₂PtCl₆.xH₂O] are decreased from 75 to 25 °C and from 2.5 to 0.25 mM, respectively. Scanning electron microscopy and high‐resolution transmission electron microscopy micrographs indicate that the more oriented samples are made of pine tree‐like structures that are effectively single crystals, and that the growth facets appear to be close to the {001} plane. This observation also clearly indicates that the plane exposed during the CV experiment is also {001}. As suggested by these micrographs, the films and nanowires are highly porous and roughness factors as large as 1000 were obtained on highly {100} oriented Pt nanowires. The predominance of {100} facets is attributed to their energetically favoured growth in the presence of hydrogen, and is shown to be significantly enhanced when the mass transport of Pt⁴⁺ is limited. Due to the predominance of {100} facets, the normalized electrocatalytic activity (μA cm^?2_Pt) for the electro‐oxidation of hydrazine and ammonia is higher than non‐oriented polycrystalline Pt by a factor of 4 and 2.7, respectively.     

Adsorbing and Activating N2 on Heterogeneous Au–Fe3O4 Nanoparticles for N2 Fixation

Electrochemical nitrogen reduction reaction (NRR) is a promising approach to convert earth‐adundant N₂ into highly value‐added NH₃. Herein, it is demonstrated that the heterogeneous Au–Fe₃O₄ nanoparticles (NPs) can be adopted as highly efficient catalysts for NRR. Due to the synergistic effect of the strong N₂ fixation ability of Fe₃O₄ and the charge transfer capability of Au, the Au–Fe₃O₄ NPs show excellent performance with a high yield (NH₃: 21.42 µg mg_cat^?1 h^?1) and a favorable faradaic efficiency (NH₃: 10.54%) at ?0.2 V (vs reversible hydrogen electrode), both of which are much better than those of the Au NPs, Fe₃O₄ NPs, as well as core@shell Au@Fe₃O₄ NPs. It also exhibits good stability with largely maintained performance after six cycles. The N₂ temperature‐programmed desorption, surface valance band spectra, and X‐ray photoelectron spectroscopy collectively confirm that Au–Fe₃O₄ NPs have a strong adsorption capacity for the reaction species and suitable surface structure for electronic transfer. The theoretical calculations reveal that Fe provides the active site to fix N₂ into *N₂H while introducing Au optimizes the adsorption of NRR intermediates, making the NRR pathway on Au–Fe₃O₄ along an energetic‐favorable process and enhancing the NRR.     

Trifunctional TiO2 Nanoparticles with Exposed {001} Facets as Additives in Cobalt‐Based Porphyrin‐Sensitized Solar Cells

In this study, highly mesoporous TiO₂ composite photoanodes composed of functional {001}‐faceted TiO₂ nanoparticles (NPs) and commercially available 20 nm TiO₂ NPs are employed in efficient porphyrin‐sensitized solar cells together with cobalt polypyridyl‐based mediators. Large TiO₂ NPs (approximately 50 nm) with exposed {001} facets are prepared using a fast microwave‐assisted hydrothermal (FMAH) method. These unique composite photoanodes favorably mitigate the aggregation of porphyrin on the surface of TiO₂ NPs and strongly facilitate the mass transport of cobalt‐polypyridyl‐based electrolytes in the mesoporous structure. Linear sweep voltammetry reveals that the transportation of Co(polypyridyl) redox is a diffusion‐controlled process, which is highly dependent on the porosity of TiO₂ films. Electrochemical impedance spectroscopy confirms that the FMAH TiO₂ NPs effectively suppress the interfacial charge recombination toward [Co(bpy)₃]³⁺ because of their oxidative {001} facets. In an optimal condition of 40 wt% addition of FMAH TiO₂ NPs in the final formula, the power conversion efficiency of the dye‐sensitized cells improves from 8.28% to 9.53% under AM1.5 (1 sun) conditions.     

Exceptional Catalytic Nature of Quantum Dots for Photocatalytic Hydrogen Evolution without External Cocatalysts

The catalytic nature of semiconducting quantum dots (QDs) for photocatalytic hydrogen (H₂) evolution can be thoroughly aroused, not because of coupling with external cocatalysts, but through partially covering controlled amount of ZnS shell on the surface. Specifically, CdSe QDs, with an optimal coverage of ZnS (≈46%), can produce H₂ gas with a constant rate of ≈306.3 ± 21.1 µmol mg^?1 h^?1 during 40 h, thereby giving a turnover number of ≈(4.4 ± 0.3) × 10⁵, which is ≈110‐fold to that of unmodified CdSe QDs under identical conditions. The performance of H₂ evolution is comparable to or even better than the commonly used external cocatalysts, e.g., metal complexes, noble metals assisted photosystems. Mechanistic insights indicate that the dramatically enhanced activity and stability of bare QDs for photocatalytic H₂ production are derived from (i) inhibiting exciton annihilation at trap states, (ii) preventing the photo‐oxidation of core frameworks, and (iii) retaining tunneling efficiencies of photogenerated electrons and holes to reactive sites with partial ZnS coverage.     

Improved Photocatalytic Performance of Heterojunction by Controlling the Contact Facet: High Electron Transfer Capacity between TiO2 and the {110} Facet of BiVO4 Caused by Suitable Energy Band Alignment

Charge separation at the interface of heterojunctions is affected by the energy band alignments of the materials that compose the heterojunctions. Controlling the contact crystal facets can lead to different energy band alignments owing to the varied electronic structures of the different crystal facets. Therefore, BiVO₄‐TiO₂ heterojunctions are designed with different BiVO₄ crystal facets at the interface ({110} facet or {010} facet), named BiVO₄‐110‐TiO₂ and BiVO₄‐010‐TiO₂, respectively, to achieve high photocatalytic performance. Higher photocurrent density and lower photoluminescence intensity are observed with the BiVO₄‐110‐TiO₂ heterojunction than those of the BiVO₄‐010‐TiO₂ heterojunction, which confirms that the former possesses higher charge carrier separation capacity than the latter. The photocatalytic degradation results of both Rhodamine B and 4‐nonylphenol demonstrate that better photocatalytic performance is achieved on the BiVO₄‐110‐TiO₂ heterojunction than the BiVO₄‐010‐TiO₂ heterojunction under visible light (≥422 nm) irradiation. The higher electron transfer capacity and better photocatalytic performance of the BiVO₄‐110‐TiO₂ heterojunction are attributed to the more fluent electron transfer from the {110} facet of BiVO₄ to TiO₂ caused by the smaller interfacial energy barrier. This is further confirmed by the selective deposition of Pt on the TiO₂ surface as well as the longer lifetime of Bi⁵⁺ in the BiVO₄‐110‐TiO₂ heterojunction.     

Phase and Composition Tuning of 1D Platinum‐Nickel Nanostructures for Highly Efficient Electrocatalysis

Among various platinum (Pt)‐based nanostructures, porous or hollow ones are of great importance because they exhibit fantastic oxygen reduction reaction (ORR) enhancements and maximize atomic utilization by exposing both exterior and interior surfaces. Here, a new class of porous Pt₃Ni nanowires (NWs) with 1D architecture, an ultrathin Pt‐rich shell, high index facets, and a highly open structure is designed via a selective etching strategy by using the phase and composition segregated Pt‐Ni NWs as the starting material. The porous feature of Pt₃Ni NWs can be readily fulfilled by changing the Pt/Ni atomic ratio of the starting Pt‐Ni NWs. Such porous Pt₃Ni NWs show extraordinary activity and stability enhancements toward methanol oxidation reaction and ORR. The porous Pt₃Ni NWs can deliver ORR mass activity of 5.60 A mg^?1, which is 37.3‐fold higher than that of the Pt/C. They also show outstanding stability with negligible activity loss after 20 000 cycles. This study offers a unique approach for the design of complex nanostructures as efficient catalysts through precisely tailoring.     

Single-Crystalline TiO2(B) Nanobelts with Unusual Large Exposed {100} Facets and Enhanced Li-Storage Capacity

The {100} facet of single-crystalline TiO₂(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single-crystalline TiO₂(B) nanobelts from H₂Ti₃O₇ with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li-storage capacity. The first-principle calculations demonstrate an ab in-plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO₂ formula with specific capacity up to 335 mAh g⁻¹, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), the cut-off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g⁻¹ after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li-ion capacity and cycle stability by tailoring the crystal orientation and nanostructures.     

Efficient Piezoelectric Energy Harvesters Utilizing (001) Textured Bimorph PZT Films on Flexible Metal Foils

Extracting energy from low vibration frequencies (<10 Hz) using piezoelectric energy harvester promises continuous self‐powering for sensors and wearables. The piezoelectric compliant mechanism (PCM) design provides a significantly higher efficiency by fostering a uniform strain for its 1st mode shape, and so is interesting for this application. In this paper, a PCM energy harvester with bimorph Pb(Zr,Ti)O₃ (PZT) films on Ni foil deposited by rf magnetron sputtering is shown to have high efficiency and large power for low frequency mechanical vibration. In particular, {001} textured PZT films are deposited on both sides of polished Ni foils with (100) oriented LaNiO₃ seed layers on HfO₂ buffer layers. The performance of PCM with an active area of 5.2 cm² is explored for various excitation accelerations (0.02–0.16 g [g = 9.8 m s^?2]) around 6 Hz. The PCM device provides a power level of 3.9 mW cm^?2 g² and 65% mode shape efficiencies.     

Orienting Active Crystal Planes of New Class Lacunaris Fe2PO5 Polyhedrons for Robust Water Oxidation in Alkaline and Neutral Media

Developing efficient and stable oxygen evolution reaction (OER) electrocatalysts is essential for realizing sustainable energy conversion, such as solar fuels. Although modulating active sites and electron transfer is of great significance to boost electrocatalysis activity, it still remains a big challenge to desirably actualize this goal. Herein, engineering of active sites and electronic framework is implemented via oriented modulation of crystal planes and construction of lacunaris architecture supported by ammonification‐elicited simultaneous incorporation of nitrogen and oxygen‐defect strategy. The new class porous nitrogen‐incorporated Fe₂PO₅ with oxygen‐defect (N‐Fe₂PO_5–x) polyhedron with dominantly exposed {110} reactive facets exhibits superior performance toward water oxidation, achieving current densities of 10 mA cm^?2 at quite low overpotentials of 235 and 315 mV in alkaline and neutral media, respectively. Furthermore, density functional theoretical calculations reveal the energetically favorable {110} planes of lower absorption energy of intermediates and remolding of electronic density framework arising from the ammoniated elicitation process, contributing to excellent OER performance of lacunaris N‐Fe₂PO_5–x polyhedrons. This work may offer a feasible guideline for regulating active sites and electron transfer to develop low‐cost and highly efficient OER electrocatalysts in energy conversion systems.     

Ultrahigh Mass Activity for the Hydrogen Evolution Reaction by Anchoring Platinum Single Atoms on Active {100} Facets of TiC via Cation Defect Engineering

Improving the platinum (Pt) mass activity for low-cost electrochemical hydrogen evolution is an important and arduous task. Here, a selective etching-reducing fluidized bed reactor technique is reported to create Ti vacancies and firmly anchor single Pt atoms on the active {100} facets of titanium carbide (TiC) to increase the Pt utilization efficiency and improve catalytic activity significantly by a synergistic effect between Ti vacancies and Pt atoms. The generated Ti vacancies are negatively charged and stabilize Pt atoms by forming covalent Pt C bonds, showing excellent long-term durability. Pt single atoms (ultralow load of 1.2 µg cm⁻²) on the defective TiC {100} show remarkable activity (24.9 mV at 10 mA cm⁻²) and a mass activity (49.69 A mg⁻¹) ≈190 times that of the state-of-the-art Pt C catalyst and nearly double the previously reported best values. The developed cation defect engineering exhibits excellent potential for fabricating next-generation advanced single-atom catalysts for large-scale hydrogen evolution at a low cost.     

Controllable hydrothermal synthesis of BiOCl nanoplates with high exposed {001} facets

Square-like bismuth oxychloride (BiOCl) nanoplates with high exposed {001} facets were successfully synthesized through a facile hydrothermal process in the presence of sodium citrate. Citric anions reduce BiOCl nanoplate size and lead to high intensity ratio of (001)–(102) by selectively absorbing on the {001} facets of BiOCl nanoparticles or nanoplates. Size of BiOCl nanoplates decrease to about 200 nm when 1.5 mmol sodium citrate was added. Thickness of BiOCl nanoplates also decreases from 100 nm to about 45 nm with increasing sodium citrate amounts. Diffraction peak intensity ratio of (001)–(102) of BiOCl nanopaltes is up to 0.93 with the adding of 1.5 mmol sodium citrate. As-obtained BiOCl nanoplates show a higher photocatalytic activity for degrading methyl orange (MO) than that prepared without sodium citrate under simulated sunlight irradiation.     

Pre-Adsorbed H-Assisted N2 Activation on Single-Atom Cadmium-O5 Decorated In2O3 for Efficient NH3 Electrosynthesis

The electrocatalytic nitrogen reduction reaction (NRR) provides a promising avenue for sustainable and decentralized green ammonia (NH₃) synthesis. To promote the NRR, the design and synthesis of efficient electrocatalysts with an elucidated reaction mechanism is critically important. Here, surface hydrogenation-facilitated NRR is demonstrated to yield NH₃ at low overpotentials on oxygen-deficient In₂O₃ plates decorated with single atom CdO₅ that have a weak N₂-binding capability. Adsorbed ^*H is calculated to be first produced via the Volmer reaction (H₂O + e⁻ → ^*H + OH⁻) and then reacts with dissolved N₂ to generate ^*N₂H₂, which is likely the rate determining step (RDS) of the whole process. Cd atoms and oxygen vacancies in In₂O₃ jointly enhance the activation of N₂ and accelerate the RDS, boosting the NRR. An NH₃ production rate of as high as 57.5 µg h⁻¹ mg_cat⁻¹ is attained at a mild potential, which is retained to a large extent even after 44 h of continuous polarization.     

Nitrogen doped anatase TiO2 sheets with dominant {001} facets for enhancing visible-light photocatalytic activity

The photocatalytic activity of TiO₂ can be mainly improved from three approaches: (1) enhancing surface energy; (2) increasing availability of visible light and (3) improving the separation efficiency of photo-induced electrons and holes. Here, we report a one-step route to obtain nitrogen (N) doped TiO₂ sheets with dominant {001} facets by a hydrothermal process. The XRD patterns confirm the better crystallinity. XPS spectrums show nitrogen acting as interstitial N or an O–Ti–N structure in TiO₂ sheets. Compared with that of TiO₂ sheets, the N doped TiO₂ sheets not only absorb visible light, but also have a large percentage of high reactive {001} facets, so the photocatalytic activities are greatly enhanced, as confirmed by the decomposition of methylene orange.     

Coupling Piezocatalysis and Photocatalysis in Bi4NbO8X (X = Cl,Br) Polar Single Crystals

Reactive oxygen species (ROS) as green oxidants are of great importance for environmental and biological applications. Photocatalysis is one of the major routes for ROS evolution, which is seriously restricted by rapid charge recombination. Herein, piezocatalysis and photocatalysis (i.e., piezo–photocatalysis) are coupled to efficiently produce superoxide radicals (?O₂^?), hydrogen peroxide (H₂O₂), and hydroxyl radicals (?OH) via oxygen reduction reaction (ORR), by using Bi₄NbO₈X (X = Cl, Br) single crystalline nanoplates. Significantly, the piezo‐photocatalytic process leads to the highest ORR performance of the Bi₄NbO₈Br nanoplates, exhibiting ?O₂^?, H₂O₂, and ?OH evolution rates of 98.7, 792, and 33.2 µmol g^?1 h^?1, respectively. The formation of a polarized electric field and band bending allows directional separation of charge carriers, promoting the catalytic activity. Furthermore, the reductive active sites are found enriched on all the facets in the piezo–photocatalytic process, also contributing to the ORR. By piezo–photodeposition of Pt to artificially plant reductive reactive sites, the Bi₄NbO₈Br plates demonstrate largely enhanced photocatalytic H₂ production activity with a rate of 203.7 µmol g^?1 h^?1. The present work advances piezo–photocatalysis as a new route for ROS generation, but also discloses the potential of piezo–photocatalytic active sites enriching for H₂ evolution.     

An Alternative Approach to Improve the Thermoelectric Properties of Half-Heusler Compounds

In this report an alternative approach for optimization of the thermoelectric properties of half-Heusler compounds is presented. The common approaches are partial substitution of elements by elements of nearby groups and substitution with homologs. In this approach we substitute one element by one neighboring element with fewer valence electrons and by one with more electrons. The amounts of the substitutions are chosen such that the amount of deficiency and excess electrons are compensated. In the solid solution TiCo_x(Ni_0.5Fe_0.5)_1-xSb\hbox{TiCo}_{x}(\hbox{Ni}_{0.5}\hbox{Fe}_{0.5})_{1-x}\hbox{Sb}, Co was substituted equally by Fe and Ni. The aim of the substitution was to improve the figure of merit by a reduction of the thermal conductivity accompanied by an unchanged high Seebeck coefficient. The solid solution TiCo_x(Ni_0.5Fe_0.5)_1-xSb\hbox{TiCo}_{x}(\hbox{Ni}_{0.5}\hbox{Fe}_{0.5})_{1-x}\hbox{Sb} was synthesized by arc-melting. The structure of the as-cast samples was analyzed by x-ray diffraction. Rietveld refinements yielded the C1_bC1_b structure type with a small amount of antisite disorder between Co and Sb. The thermoelectric properties of the solid solution were investigated in the temperature range from 2 K to 400 K. A Seebeck coefficient of -260 mV K^-1-260\,\mu\hbox{V\,K}^{-1} at 400 K and a reduction of the thermal conductivity to 3 Wm^-1 K^-13\,\hbox{Wm}^{-1}\,\hbox{K}^{-1} were measured. The figure of merit was enhanced by a factor of about seven to a value of 0.04 at 400 K for TiCo_0.8(Ni_0.1Fe_0.1)Sb\hbox{TiCo}_{0.8}(\hbox{Ni}_{0.1}\hbox{Fe}_{0.1})\hbox{Sb}.