Active Surface Research Articles

Developing TiCo2O4 spinel based on rGO nanosheet to enhance electrochemical performance of OER activity

The reduction of fossil fuel reserves and the deterioration of environmental conditions have led to a worldwide concern with producing significant amounts of energy in a sustainable manner. The production of electrocatalysts for the oxygen evolution reaction (OER) is imperative for widespread commercialization of water electrolyzers. The electrocatalysts must exhibit improved electrocatalytic behavior while being cost-effective. This work presents simple hydrothermal route for producing a TiCo2O4 nanostructure with a spherical morphology, which is supported on reduced graphene oxide sheets (rGO). The nanocomposite has been subjected to an investigation of its morphological, structural and electrochemical characteristics. This material exhibits promise for electrochemical water splitting due to its significant electroactive surface area, distinctive morphology and metal ions (M+) synergetic effect on its electrocatalytic performance. The nanostructure of TiCo2O4/rGO-has been observed to exhibit robust electrocatalytic activity, underscoring the significance of the present study. Additionally, presented are the enduring stability of the OER, along with the reduced overpotential (269 mV@10 mA cm−2), decreased Tafel slope (37.56 mV dec-1) with greater electrochemical active surface area. Our finding suggests that the TiCo2O4/rGO nanohybrid exhibited high electrocatalytic efficiency and can be utilized in diverse electrochemical applications.

Hydrogen generation by hydrolysis of alkaline NaBH4 solution doped with amorphous catalyst Co–Y2O3–B/CNTs

This investigation enhances the catalytic efficiency of Co–B/CNTs for hydrogen production via sodium borohydride hydrolysis by doping with 5%Y2O3. Such doping significantly boosts hydrogen evolution rates, with Co–Y2O3–B/CNTs achieving a production rate of 1083.43 ml g−1·min−1—surpassing Co–B/CNTs by 1.5 times and tripling that of Co–B catalysts. SEM and XRD analyses show Y2O3 doping reduces particle aggregation and maintains the catalyst's amorphous state, thereby increasing the active surface area. Furthermore, XPS analysis demonstrates that introducing yttrium into Co–B/CNTs catalysts improves their surface elemental composition and valence states. This improvement boosts catalyst performance and stability by enhancing electron transfer and particle size optimization. Optimal hydrolysis is achieved at an NaOH concentration of 2.5 mol/L, with higher concentrations diminishing hydrogen production due to increased viscosity from by-product formation. Additionally, Co–Y2O3–B/CNTs catalysts exhibit commendable durability, maintaining more than two-thirds of their initial activity after five reuse cycles, outperforming comparable catalysts to a moderate extent. These findings underscore the beneficial role of Y2O3 in the Co–B/CNTs framework, promoting Y2O3-doped catalysts for their enhanced efficiency, sustainability, and hydrogen production capabilities.

Secure Active Intelligent Reflecting Surface Communication against Colluding Eavesdroppers

An active intelligent reflecting surface (IRS)-assisted, secure, multiple-input–single-output communication method is proposed in this paper. In this proposed scheme, a practical and unfavorable propagation environment is considered by assuming that multiple colluding eavesdroppers (Eves) coexist. In this case, we jointly optimize the beamformers of the base station (BS) and the active IRS for the formulated sum secrecy rate (SSR) maximization problem. Because the formulated problem is not convex, we apply the alternating optimization method to optimize the beamformers for maximizing the SSR. Specifically, we use the semi-definite relaxation method to solve the sub-problem of the beamforming vector of the BS, and we use the successive convex approximation method to solve the sub-problem of the power amplification matrix of the active IRS. Based on the solutions obtained using these stated methods, numerical results show that deploying an active IRS is superior compared to the cases of a passive IRS and a non-IRS for improving the physical layer security of wireless communication with multiple colluding Eves under different settings, such as the numbers of users, Eves, reflecting elements, and BS antennas as well as the maximum transmit power budget at the BS.

Incorporation of Pd Catalyst into Highly Effective Borophene Nanosheet Co-Catalyst for Electrokinetics and Electrochemical Oxygen Reduction Reactions

AbstractTo improve the performance of the system, it is of great importance to develop efficient catalysts for ethanol (EtOH) electro-oxidation. Pd/B electrocatalyst was synthesized using a sonochemical method. Structural and electrochemical properties of the prepared nanomaterial were investigated using electrochemical and physical techniques such as Raman spectroscopy, electrochemical impedance spectroscopy (EIS), x-ray diffraction (XRD), zetersizer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive x-ray spectroscopy (EDS) and cyclic voltammetry (CV). FTIR confirmed all the functional groups of carbon black, Pd/C, borophene, and Pd/B, and the crystallinity was investigated using XRD. EIS showed that Pd/B has a faster charge transfer and, through investigation using CV, Pd/B showed a more negative onset potential and higher current (−0.76 V vs. Ag|AgCl; 0.07 mA) than Pd/C (−0.65 V vs. Ag|AgCl; 0.05 mA), indicating a more catalytic behavior and tolerance of Pd/B. The active sites could be attributed to the addition of borophene. During the anodic sweeping direction of Pd/B electrocatalyst, it was observed that the ratio of backward peak current (Ibwd) to forward peak current (Ifwd), (Ibwd/Ifwd) of in a 2 M of NaOH + 2 M of EtOH is almost equal to (Ibwd/Ifwd) 1 which shows excellent tolerance of Pd/B to poisoning by ethanol intermediate species. The electron transfer rate (Ks) values for Pd/B at 0.1 M, 0.5 M, 1 M, 1.5 M, and 2 M were estimated to be 4.50 × 10−13 s−1, 1.08 × 10−12 s−1, 4.28 × 10−13 s−1, 5.25 × 10−14 s−1 and 9.35 × 10-14 s−1. At 2 M there is a faster electron transfer than at other concentrations which is also evidenced by the obtained diffusion values (D) of the system which were found to be 2.92 × 10−7 cm2 s−1, 4.72 × 10−8 cm2 s−1, 4.82 × 10−8 cm2 s−1, 1.22 × 10−7 cm2 s−1, and 9.12 × 10−8 cm2 s−1. The electrochemically active surface area (ECSA) is strongly related to intrinsic activity, Pd/B (1.85 cm2/mg × 10−5 cm2/mg) denotes the highest Pd-O stripping charge than Pd/C (1.13 cm2/mg × 10−5 cm2/mg).

Urchin-Like Mesoporous TiN Hollow Sphere Enabling Promoted Electrochemical Kinetics of Bromine-Based Flow Batteries.

Bromine-based flow batteries (BFB) have always suffered from poor kinetics due to the sluggish Br3 -/Br- redox, hindering their practical applications. Developing cathode materials with high catalytic activity is critical to address this challenge. Herein, the in-depth investigation for the free energy of the bromine redox electrode is conducted initially through DFT calculations, establishing the posterior desorption during oxidation as the rate-determining step. An urchin-like titanium nitride hollow sphere (TNHS) composite is designed and synthesized as the catalyst for bromine redox. The large difference in Br- and Br3 - adsorption capability of TNHS promotes rapid desorption of generated Br3 - during the oxidation process, liberating active sites timely to enable smooth ongoing reactions. Besides, the urchin-like microporous/mesoporous structure of TNHS provides abundant active surface for bromine redox reactions, and ample cavities for the bromine accommodation. The inherently high conductivity of TNHS enables facile electron transfer through multiple channels. Consequently, zinc-bromide flow batteries with TNHS catalyst exhibit significantly enhanced kinetics, stably operating at 80mAcm-2 with 82.78% energy efficiency. Overall, this study offers a solving strategy and catalyst design approach to the sluggish kinetics that has plagued bromine-based flow batteries.

Achieving Exceptional Volumetric Desalination Capacity Using Compact MoS2 Nanolaminates.

Capacitive deionization (CDI) has emerged as a promising technology for freshwater recovery from low-salinity brackish water. It is still inapplicable in specific scenarios (e.g., households, islands, or offshore platforms) due to too low volumetric adsorption capacities. In this study, we report a high-density semi-metallic molybdenum disulfide (1T'-MoS2) electrode with compact architecture obtained by restacking of exfoliated nanosheets, which achieved high capacitance up to ∼277.5 F cm-3 under an ultrahigh scan rate of 1000mV s-1 with a lower charge-transfer resistance and nearly ten-fold higher electrochemical active surface area than the 2H-MoS2 electrode. Furthermore, 1T'-MoS2 electrode demonstrates exceptional volumetric desalination capacity of 65.1 mgNaCl cm-3 in CDI experiments. Ex-situ X-ray diffraction (XRD) reveal that the cation storage mechanism with the dynamic expansion of 1T'-MoS2 interlayer to accommodate cations such as Na+, K+, Ca2+, and Mg2+, which in turn enhances the capacity. Theoretical analysis unveils that 1T' phase is thermodynamically preferable over 2H phase, the ion hydration and channel confinement also play critical role in enhancing ion adsorption. Overall, this work provides a new method to design compact two-dimensional layered nanolaminates with high volumetric performance for CDI desalination. This article is protected by copyright. All rights reserved.

Structurally Tunable Graphitized Mesoporous Carbon for Enhancing the Accessibility and Durability of Cathode Pt‐Based Catalysts for Proton Exchange Membrane Fuel Cells

Low Pt utilization and intense carbon corrosion of cathode catalysts is a crucial issue for high‐efficiency proton exchange membrane fuel cells due to the highly demanded long‐term durability and less acquisition/application cost. Herein, structurally tunable graphitized mesoporous carbon (GMC) is obtained by direct high‐temperature pyrolysis and in situ‐controlled mesopore formation; the structure‐optimized GMC1300‐1800 exhibits a mesopore size of 7.54 nm and enhanced corrosion resistance. Functionalized GMC1300‐1800 is loaded with small‐sized Pt nanoparticles (NPs) (1.5 nm) uniformly by impregnation method to obtain Pt/GMC1300‐1800 and form an “internal platinum structure” to avoid sulfonic acid groups poisoning as well as ensure O2/proton accessibility. Hence, the electrochemically active surface area (ECSA) of Pt/GMC1300‐1800 reaches 106.1 m2 g−1Pt, while mass activity and specific activity at 0.9 V are 2.1 and 1.4 times those of commercial Pt/C, respectively. Notably, the ECSA decay is less than 17% for both 30 000 cycles’ accelerated durability tests (ADTs) of Pt attenuation and carbon attenuation. Accordingly, the optimized mesoporous structure of GMC1300‐1800 significantly decreases the coverage of sulfonic acid groups on Pt NPs, leading to the highest peak power density in the single‐cell test. Density functional theory calculations demonstrate the synergistic effect between graphitization and mesoporosity on enhancing the accessibility and durability of the catalysts.

Construction of structurally engineered NiCo2O4 nanostructures as a bifunctional electrocatalyst for high-performance overall water splitting

The development of low-cost and highly efficient bifunctional electrocatalysts for overall water splitting is a challenging but urgent goal. Herein, nickel cobaltite (NiCo2O4) with different morphologies was developed for electrocatalytic overall water splitting. Encouragingly, the NiCo2O4 nanoneedle arrays required competitive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) overpotentials of 106 and 310 mV to achieve a density of 10 mA cm−2 (j10) in KOH media, respectively. Furthermore, the as-made nanoneedle electrocatalyst employed as both anode and cathode, which displayed a low voltage of 1.67 Vto attain j10, with satisfactory durability for 50 h. The nanoneedle morphology not only improves the electrochemical active surface area, but also helpful to boost the charge transfer ability of NiCo2O4 and control the adsorption of reaction intermediates in water splitting. These results demonstrate the feasibility of the NiCo2O4 nanostructure by altering the active sites using morphology to develop the electrocatalytic activity of the materials.

Improvement of hydrogen production via aqueous phase reforming of glycerol with Ni-Co catalysts synthesized through controlled urea matrix combustion

The effect of synthesis variable control during the combustion of urea in solution to obtain a Ni-Co/γ-Al2O3 catalyst with a low metallic loads for producting hydrogen by reforming glycerol was studied. Catalysts with the same urea/metal molar ratio but synthesized by controlled or uncontrolled urea matrix combustion were compared. It has been observed that adopting a urea/metal molar ratio between 2 and 6 and a heating rate of 10 °C∙min−1 results in a catalyst with an active surface and high Ni-Co interaction. This leads to significant improvements in H2 yield (from 34 to 50%), glycerol conversion (from 35 to 50%), and H2 selectivity (from 96 to 99%), while maintaining stability during 420 min of reaction. The repeatability of controlled synthesis has shown differences in results of less than 2%. Controlled synthesis is an attractive approach for scaling up the process for treating glycerinous waters, effluents in biodiesel plants.

Durability Investigation of Low Pt-Loaded PEM Fuel Cells with Different Catalyst Layer Morphologies

This study investigates the durability of proton exchange membrane fuel cells against the Pt-dissolution degradation mechanism using a triangular accelerated stress test (AST) within the voltage range of 0.6-1 V. The electrochemical active surface area and polarization curves are reported throughout the AST for three different catalyst layers (CL), all featuring 0.1 mg/cm2 Pt loading but with different morphologies, which include the Pt/C weight percentages, dilution ratio, and thickness. In addition, a numerical model is employed to simulate the electrochemical performance of these samples at the beginning and end of life, considering the variations in the oxygen transport resistances and catalyst structure.

Hydrothermally Synthesized Cerium Phosphate with Functionalized Carbon Nanofiber Nanocomposite for Enhanced Electrochemical Detection of Hypoxanthine

This work presents the detection of hypoxanthine (HXA), a purine derivative that is similar to nucleic acids who overconsumption can cause health issues, by using hydrothermally synthesized cerium phosphate (CePO4) followed by a sonochemical approach for CePO4 decorated with a functionalized carbon nanofiber (CePO4@f-CNF) nanocomposite. The formation of the nanocomposite was confirmed with X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). A CePO4@f-CNF nanocomposite is used to modify a glassy carbon electrode (GCE) to analyze the electrochemical detection of HXA. Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), and Differential pulse voltammetry (DPV) were used to examine the electrochemical properties of the composite. As a result, the modified electrode exhibits a larger active surface area (A = 1.39 cm2), a low limit of detection (LOD) at 0.23 µM, a wide linear range (2.05–629 µM), and significant sensitivity. Therefore, the CePO4@f-CNF nanocomposite was used to study the real-time detection in chicken and fish samples, and it depicted significant results.

Accelerating the Screening of Modified MA2Z4 Catalysts for Hydrogen Evolution Reaction by Deep Learning‐Based Local Geometric Analysis

Machine learning (ML) integrated with density functional theory (DFT) calculations have recently been used to accelerate the design and discovery of single‐atom catalysts (SACs) by establishing deep structure–activity relationships. The traditional ML models are always difficult to identify the structural differences among the single‐atom systems with different modification methods, leading to the limitation of the potential application range. Aiming to the structural properties of several typical two‐dimensional MA2Z4‐based single‐atom systems (bare MA2Z4 and metal single‐atom doped/supported MA2Z4), an improved crystal graph convolutional neural network (CGCNN) classification model was employed, instead of the traditional machine learning regression model, to address the challenge of incompatibility in the studied systems. The CGCNN model was optimized using crystal graph representation in which the geometric configuration was divided into active layer, surface layer, and bulk layer (ASB‐GCNN). Through ML and DFT calculations, five potential single‐atom hydrogen evolution reaction (HER) catalysts were screened from chemical space of 600 MA2Z4‐based materials, especially V1/HfSn2N4(S) with high stability and activity (ΔGH* is 0.06 eV). Further projected density of states (pDOS) analysis in combination with the wave function analysis of the SAC‐H bond revealed that the SAC‐dz2 orbital coincided with the H‐s orbital around the energy level of −2.50 eV, and orbital analysis confirmed the formation of σ bonds. This study provides an efficient multistep screening design framework of metal single‐atom catalyst for HER systems with similar two‐dimensional supports but different geometric configurations.

One‐Step Synthesis of Phase‐Controlled Co2P Nanoparticles as an Electrocatalyst for Hydrogen Evolution Reaction

AbstractCobalt phosphides have been investigated as potentially useful electrocatalysts for accelerating hydrogen evolution. Cobalt phosphide electrocatalysts are synthesized in a single step at varied phosphating temperatures (350, 400, 450 °C) via the gas phase approach. Synthesized at a phosphating temperature of 350 °C, Co2P (CP‐350) transforms into a mixed phase that contains both Co2P and CoP (CP‐400 and CP‐450) as the phosphating temperature goes up which is confirmed by XRD. CP‐350, CP‐400, and CP‐450 exhibited overpotentials of 181, 270, and 293 mV respectively with Tafel slopes of 112, 146, and 175 mV/dec. In contrast to CP‐400 and CP‐450, CP‐350 revealed superior hydrogen evolution reaction (HER) performance and stability for up to 12 h due to its pure phase (Co2P), high surface area (151 m2/g), and high electrochemical surface area (7.02 cm2) with low charge transfer resistance. According to our work, changing the phase and active surface area of transition metal phosphide catalysts can greatly increase their HER catalytic efficiency.

Silica Confinement for Stable and Magnetic Co−Cu Alloy Nanoparticles in Nitrogen‐Doped Carbon for Enhanced Hydrogen Evolution

AbstractAmmonia borane (AB) with 19.6 wt % H2 content is widely considered a safe and efficient medium for H2 storage and release. Co‐based nanocatalysts present strong contenders for replacing precious metal‐based catalysts in AB hydrolysis due to their high activity and cost‐effectiveness. However, precisely adjusting the active centers and surface properties of Co‐based nanomaterials to enhance their activity, as well as suppressing the migration and loss of metal atoms to improve their stability, presents many challenges. In this study, mesoporous‐silica‐confined bimetallic Co−Cu nanoparticles embedded in nitrogen‐doped carbon (CoxCu1−x@NC@mSiO2) were synthesized using a facile mSiO2‐confined thermal pyrolysis strategy. The obtained product, an optimized Co0.8Cu0.2@NC@mSiO2 catalyst, exhibits enhanced performance with a turnover frequency of 240.9 molH2 ⋅ molmetal ⋅ min−1 for AB hydrolysis at 298 K, surpassing most noble‐metal‐free catalysts. Moreover, Co0.8Cu0.2@NC@mSiO2 demonstrates magnetic recyclability and extraordinary stability, with a negligible decline of only 0.8 % over 30 cycles of use. This enhanced performance was attributed to the synergistic effect between Co and Cu, as well as silica confinement. This work proposes a promising method for constructing noble‐metal‐free catalysts for AB hydrolysis.

Silica Confinement for Stable and Magnetic Co-Cu Alloy Nanoparticles in Nitrogen-Doped Carbon for Enhanced Hydrogen Evolution.

Ammonia borane (AB) with 19.6 wt % H2 content is widely considered a safe and efficient medium for H2 storage and release. Co-based nanocatalysts present strong contenders for replacing precious metal-based catalysts in AB hydrolysis due to their high activity and cost-effectiveness. However, precisely adjusting the active centers and surface properties of Co-based nanomaterials to enhance their activity, as well as suppressing the migration and loss of metal atoms to improve their stability, presents many challenges. In this study, mesoporous-silica-confined bimetallic Co-Cu nanoparticles embedded in nitrogen-doped carbon (CoxCu1-x@NC@mSiO2) were synthesized using a facile mSiO2-confined thermal pyrolysis strategy. The obtained product, an optimized Co0.8Cu0.2@NC@mSiO2 catalyst, exhibits enhanced performance with a turnover frequency of 240.9 molH2 ⋅ molmetal ⋅ min-1 for AB hydrolysis at 298 K, surpassing most noble-metal-free catalysts. Moreover, Co0.8Cu0.2@NC@mSiO2 demonstrates magnetic recyclability and extraordinary stability, with a negligible decline of only 0.8 % over 30 cycles of use. This enhanced performance was attributed to the synergistic effect between Co and Cu, as well as silica confinement. This work proposes a promising method for constructing noble-metal-free catalysts for AB hydrolysis.

Polarity-driven three-dimensional spontaneous rotation of a cell doublet

AbstractMechanical interactions between cells play a fundamental role in the self-organization of organisms. How these interactions drive coordinated cell movement in three dimensions remains unclear. Here we report that cell doublets embedded in a three-dimensional extracellular matrix undergo spontaneous rotations. We investigate the rotation mechanism and find that it is driven by a polarized distribution of myosin within cell cortices. The mismatched orientation of this polarized distribution breaks the doublet mirror symmetry. In addition, cells adhere at their interface through adherens junctions and with the extracellular matrix through focal contacts near myosin clusters. We use a physical theory describing the doublet as two interacting active surfaces to show that rotation is driven by myosin-generated gradients of active tension whose profiles are dictated by interacting cell polarity axes. We also show that three-dimensional shape symmetries are related to broken symmetries of the myosin distribution in cortices. To test for the rotation mechanism, we suppress myosin clusters using laser ablation and generate new myosin clusters by optogenetics. Our work clarifies how polarity-oriented active mechanical forces drive collective cell motion in three dimensions.

Bifunctional Strontium Cobalt Molybdenum Oxide (Sr2CoMoO6) Perovskite as an Efficient Catalyst for Electrochemical Water Splitting Reactions in Alkaline Media

Developing earth‐abundant low‐cost electrocatalysts is of prime research interest towards the need for clean energy technology, such as water‐splitting reactions. Herein, we have explored the electrocatalytic activity of the double perovskite‐based strontium cobalt molybdenum oxide (SCMO) towards water‐splitting reactions, both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Prepared by scalable autocombustion synthesis, the as‐synthesised bulk SCMO perovskite exhibited impressive electrocatalytic performance attributed to its substantial electrochemical active surface area. For the OER, it exhibited an overpotential of 350 mV with a Tafel slope value of 76 mV/dec. Concurrently, it showed proficient activity in the HER, revealing an overpotential of 270 mV and a Tafel slope of 112 mV/dec. Further, this perovskite material was stable during continuous electrocatalysis over a 24 h period with a negligible increase in observed overpotential value. The electronic density of states confirmed that the Co plays a pivotal role in enhancing electrocatalytic activities. This is achieved by a substantial reduction in the band gap and enhancement of the d‐band centre to an optimal level, rendering the system more favourable for electrocatalytic reactions. Our study contributes insights to the advancement of the design and utilization of perovskite‐based catalysts in the realm of sustainable energy technologies.

Electrocatalytic Oxygen Reduction Using Metastable Zirconium Suboxide

Strategies for discovery of high‐performance electrocatalysts are important to advance clean energy technologies. Metastable phases such as low temperature or interfacial structures that are difficult to access in bulk may offer such catalytically active surfaces. We report here that the suboxide Zr3O, which is formed at Zr‐ZrO2 interfaces but does not appear in the experimental Zr‐O phase diagram exhibits outstanding oxygen reduction reaction (ORR) performance surpassing that of benchmark Pt/C and most transition metal‐based catalysts. Addition of Fe3C nanoparticles to give a Zr‐Zr3O‐Fe3C/NC catalyst (NC = nitrogen‐doped carbon) gives a half‐wave potential (E1/2) of 0.914 V, outperforming Pt/C and showing only a 3 mV decrease after 20,000 electrochemical cycles. A zinc‐air battery (ZAB) using this cathode material has a high power density of 241.1 mW cm‐2 and remains stable for over 50 days of continuous cycling, demonstrating potential for practical applications. Zr3O demonstrates that interfacial or other phases that are difficult to stabilize may offer new directions for the discovery of high‐performance electrocatalysts.

Electrocatalytic Oxygen Reduction Using Metastable Zirconium Suboxide.

Strategies for discovery of high-performance electrocatalysts are important to advance clean energy technologies. Metastable phases such as low temperature or interfacial structures that are difficult to access in bulk may offer such catalytically active surfaces. We report here that the suboxide Zr3O, which is formed at Zr-ZrO2 interfaces but does not appear in the experimental Zr-O phase diagram exhibits outstanding oxygen reduction reaction (ORR) performance surpassing that of benchmark Pt/C and most transition metal-based catalysts. Addition of Fe3C nanoparticles to give a Zr-Zr3O-Fe3C/NC catalyst (NC = nitrogen-doped carbon) gives a half-wave potential (E1/2) of 0.914 V, outperforming Pt/C and showing only a 3 mV decrease after 20,000 electrochemical cycles. A zinc-air battery (ZAB) using this cathode material has a high power density of 241.1 mW cm-2 and remains stable for over 50 days of continuous cycling, demonstrating potential for practical applications. Zr3O demonstrates that interfacial or other phases that are difficult to stabilize may offer new directions for the discovery of high-performance electrocatalysts.

Self-diffusiophoretic propulsion of a spheroidal particle in a shear-thinning fluid

Shear-thinning viscosity is a non-Newtonian behaviour that active particles often encounter in biological fluids such as blood and mucus. The fundamental question of how this ubiquitous non-Newtonian rheology affects the propulsion of active particles has attracted substantial interest. In particular, spherical Janus particles driven by self-diffusiophoresis, a major physico-chemical propulsion mechanism of synthetic active particles, were shown to always swim slower in a shear-thinning fluid than in a Newtonian fluid. In this work, we move beyond the spherical limit to examine the effect of particle eccentricity on self-diffusiophoretic propulsion in a shear-thinning fluid. We use a combination of asymptotic analysis and numerical simulations to show that shear-thinning rheology can enhance self-diffusiophoretic propulsion of a spheroidal particle, in stark contrast to previous findings for the spherical case. A systematic characterization of the dependence of the propulsion speed on the particle's active surface coverage has also uncovered an intriguing feature associated with the propulsion speeds of a pair of complementarily coated particles not previously reported. Symmetry arguments are presented to elucidate how this new feature emerges as a combined effect of anisotropy of the spheroidal geometry and nonlinearity in fluid rheology.