Methanol Tolerance Research Articles

Bacillus Subtilis-Derived Carbon Nanorods as Efficient ORR Electrocatalysts

Developing high-performance anion-exchange membrane fuel cells requires stable and highly active oxygen reduction (ORR) catalysts. To fabricate cheap and efficient porous carbon materials for ORR, heteroatom-doped carbon nanorods were synthesized by pyrolyzing Bacillus subtilis. The obtained carbon material maintained the uniformly distributed nanorods as original Bacillus subtilis and had inherent doped heteroatom. The obtained BS-2.0 had the highest specific surface area (209.04 m2 g−1) and the maximum ID/IG (1.0372). Its starting potential (0.93 V vs RHE) and semi-wave potential (0.81 V vs RHE) were close to 20% commercial Pt/C, and its ultimate current density was 3.98 mA cm−2@1600 rpm. Meanwhile, the stability of cycling potentiates polarization, and methanol tolerance of BS-2.0 were all greater than 20% commercial Pt/C. It was the inherent heteroatom, well-distributed nanorods, abundant pore distribution, and large surface area that contributed to its excellent electrochemical performance.

NC Loaded PtM Alloy from M-NC with Ultralow Pt Loading for Oxygen Reduction Reaction

Developing low Pt or non-precious metal catalysts for oxygen reduction reaction (ORR) has becoming necessary in recent years. Herein, PtM alloy anchored on nitrogen-doped carbon (PtM/NC, M=Fe, Co) catalyst with ultralow Pt loading (∼1 wt%) is prepared from the simple two-process pyrolysis, namely from C to M-NC then to PtM/NC. The as-prepared PtM/NC (M=Fe, Co) shows an excellent ORR catalytic performance with the peak potential and half-wave potential of 0.901 and 0.870 V for PtFe/NC, 0.868 and 0.845 V for Pt3Co/NC. The ORR on PtM/NC (M=Fe, Co) is a mainly direct 4-electron reaction pathway (3.75–3.90) in alkaline solution. Moreover, they possess good methanol tolerance and stability. Synergistic effect of Pt and M together with N species result in the excellent ORR catalytic activity of PtM/NC (M=Fe, Co). The negative shift of Pt binding energy caused by both lattice contraction and electron orbital coupling from M is beneficial for reducing the d-band center of Pt, weakening the oxygen binding energy and enhancing the ORR intrinsic activity of Pt. The strong interactions between NC and PtM alloy are beneficial for anchoring PtM nanoparticles, promoting the stability of catalyst. This work provides a new strategy for preparing ultralow Pt loading catalysts.

Chitosan-derived carbon sphere with self-activating behavior for stable oxygen reduction reaction in acid and alkaline media

Utilizing shrimp waste-derived Chitosan as biomass source, we developed metal-free nitrogen and sulfur-doped porous carbon (NSPC) with a high specific surface area of 609.53 m2/g as a remarkable electrocatalyst for oxygen reduction reaction (ORR), surpassing benchmark Pt/C with half-wave (0.8574 V) and onset (0.9573 V) potentials in alkaline (0.1 M KOH) media. Besides high electrocatalytic activity, NSPC-800 showed excellent methanol tolerance ability and significantly low hydrogen peroxide yields (H2O2) of 5 % and 8 % in 0.1 M KOH and 0.5 M H2SO4, which is comparably lower than the previously reported chitosan based non-precious catalysts. Interestingly NSPC-800 displays robust stability in 0.1 M KOH electrolyte, improving the current retention rate from 89.17 % to 95.18 % over an increased operation period, evidencing its self-activating characteristics. This self-activating stability is also mirrored in 0.5 M H2SO4 where both fresh and recycled (after 5000 CV cyles) NSPC-800 catalysts retained more than half of their initial current. Additionally, to identify the nature of the active sites, the ORR measurements were correlated with ex-situ spectroscopy for post-stability of fresh and recycled NSPC-800 catalysts revealed dynamic reconfiguration of nitrogen, sulfur, and oxygen active sites evidenced compared to the pre-stability elemental surface, indicating an adaptive response of the catalyst to the harsh operating environment. In the future, our biomass-derived NSPC-800 will pave the way to develop cost-effective and highly efficient catalysts from waste to energy devices promising a twin-goal approach, contributing to the circular economy and sustainable development goals.

Superior Catalytic Performance and Methanol Tolerance of Co@Mesoporous Graphene Nanocomposites toward Oxygen Reduction Reaction

AbstractThe global energy crisis and growing concerns about environmental pollution have spurred researchers to explore eco‐friendly methods of generating clean energy. Previous studies have often relied on noble metal catalysts to facilitate oxygen reduction reactions (ORR) in energy production reactions. However, their high cost has limited their widespread adoption, making the development of highly active and affordable ORR catalysts a significant challenge. In this study, a vacuum heat treatment technique was employed to fabricate a cobalt‐loaded mesoporous graphene (Co−Gs) nanocomposite. The inclusion of cobalt in graphene enhances the reaction, while the presence of mesoporous graphene provides a larger surface area to accommodate the active sites of Co. This synergistic effect promotes the improvement of catalytic performance. Additionally, the stability and methanol tolerance of Co−Gs nanocomposites is also superior than that of Pt−C. The excellent catalytic performance of the Co−Gs nanocomposite is attributed to a four‐electron pathway within the nanocomposite, as demonstrated by electrocatalytic kinetics investigations. Additionally, the interface interaction between the Co nanoparticles and Gs enhances the efficiency of electron transfer, effectively improving the catalytic performance. These findings highlight the potential of Co‐loaded graphene nanocomposites as highly efficient and cost‐effective electrocatalysts for clean energy application.

Co-NC catalyst with rich coordinated nitrogen and hierarchical porous structure for oxygen reduction reaction

Cobalt nitrogen-doped carbon (Co-NC) catalysts are synthesized for oxygen reduction reaction (ORR) via the pyrolysis of zinc-mediated and SiO2-templated 2,6-diaminopyridine (DAP) composites. The resulting Co-NC(Zn12-SiO2[20])-900 demonstrates exceptional ORR activities, with half-wave and onset potentials of 0.835 V and 0.875 V, respectively, which is similar to Pt/C catalyst. In long-term durability test, the Co-NC(Zn12-SiO2[20])-900 catalyst exhibits a negligible E1/2 shift, and in methanol tolerance tests, it displays significantly better performance than commercial Pt/C catalyst. The superior performance can be attributed to the hierarchical porous structure, dense and highly accessible Co-N4 and graphitic nitrogen (g-N) sites. The high content of Co-N4 and g-N sites enhances 3d-orbital filling and reduces the Co centers' on-site magnetic moment, as calculated by density functional theory. This may lead to a decrease in the energy barrier of the rate-determining step (RDS), which in turn enhances the intrinsic activity of the ORR.

The manipulation of rectifying contact of Co and nitrogen‐doped carbon hierarchical superstructures toward high‐performance oxygen reduction reaction

AbstractRational design and construction of oxygen reduction reaction (ORR) electrocatalysts with high activity, good stability, and low price are essential for the practical applications of renewable energy conversion devices, such as metal‐air batteries. Electronic modification through constructing metal/semiconductor Schottky heterointerface represents a powerful strategy to enhance the electrochemical performance. Herein, we demonstrate a concept of Schottky electrocatalyst composed of uniform Co nanoparticles in situ anchored on the carbon nanotubes aligned on the carbon nanosheets (denoted as Co@N‐CNTs/NSs hereafter) toward ORR. Both experimental findings and theoretical simulation testify that the rectifying contact could impel the voluntary electron flow from Co to N‐CNTs/NSs and create an internal electric field, thereby boosting the electron transfer rate and improving the intrinsic activity. As a consequence, the Co@N‐CNTs/NSs deliver outstanding ORR activity, impressive long‐term durability, excellent methanol tolerance, and good performance as the air‐cathode in the Zn‐air batteries. The design concept of Schottky contact may provide the innovational inspirations for the synthesis of advanced catalysts in sustainable energy conversion fields.

Bimetallic Organic Frameworks via In Situ Solvothermal Sol-Gel-Crystal and Sol-Crystal Transformation as Durable Electrocatalysts for Oxygen Reduction Reaction.

The in situ solvothermal conversion of metal-organic gels (MOGs) to crystalline metal-organic frameworks (MOFs) represents a versatile and ingenious strategy that has been employed for the synthesis of MOF materials with specific morphologies, high yield, and improved functional properties. Herein, we have adopted an in situ solvothermal conversion of bimetallic MOGs to crystalline bimetallic MOFs with the aim of introducing a redox-active metal heterogeneity into the monometallic counterpart. The formation of bimetallic NiZn-MOF and CoZn-MOF via in situ solvothermal sol-gel-crystal and sol-crystal transformation is found to depend on the solvent systems used. The sol-to-gel-to-crystal transformation of NiZn-MOF via the formation of NiZn-MOG is found to occur through the gradual disruption of gel fibers leading to subsequent formation of microcrystals and single crystals of NiZn-MOF. These bimetallic MOFs and MOGs serve as promising electrocatalysts for oxygen reduction reaction (ORR) with an excellent methanol tolerance property, which can be attributed to the enhanced mass and charge transfer, higher oxygen vacancies, and bimetallic synergistic interactions among the heterometals. This work demonstrates a convenient strategy for producing bimetallic MOGs to MOFs through the introduction of a redox-active metal heterogeneity in the inorganic hybrid functional materials for fundamental and applied research. Our results connect MOGs and MOFs which have been regarded as having opposite physical states, that is, soft vs hard, and provide promising structural correlation between MOGs and MOFs at the molecular level.

Ligin-derived graphene-like ultrathin carbon materials for ORR catalysis

Low-cost nitrogen-doped carbon materials with graphene-like structures were designed and prepared from extensive renewable biomass waste lignin. The obtained carbon materials exhibited well-designed ultrathin two-dimensional structures with high specific area and mesoporous characteristics. Benefiting from the well-designed structures with extensive catalytic active sites and efficient mass transfer and diffusion, as well as the modified electronic characteristics from nitrogen doping, the lignin-derived carbon materials exhibited pronounced ORR catalytic activity and methanol tolerance. Considering these, the lignin-derived carbon materials hold great application potentials as ORR catalysts and catalyst supports.

A hybrid cathode catalytic layer composed of M–N–C and Pt/C for direct methanol fuel cells with high methanol tolerance

Pt/C based direct methanol fuel cells (DMFCs) always suffer from a serious methanol crossover under a high concentration of methanol solution. In this paper, we report a novel hybrid cathode catalytic layer (CCL) consisting of a physical blend of Pt/C and Fe-N-C. DMFC based on the hybrid CCL with an optimized loadings (0.25 mg cm−2 Fe-N-C and 2 mgPt cm-2Pt/C) outputs a high power density of 28.87 mW cm−2 at 10 M methanol, and the single Pt/C based cell only shows a low power density of 12.04 mW cm−2 in comparison. Such a large improvement attributes to the increasing amount of reactive oxygen species (ROS), which is produced by Fe-N-C via an incomplete four-electron transfer process in oxygen reduction reaction (ORR). Inspired by this strategy, several M−N−C catalysts were synthesized, among which Cu-N-C shows the most brilliant performance to enhance the methanol tolerance of Pt/C. The peak power density of DMFC with Cu-N-C based hybrid CCL exceeds 31 mW cm−2 at 10 M methanol, which is superior to that of cells with Fe-N-C based hybrid CCL. This work provides a new approach for designing DMFCs with high energy density, which is practical for applications of portable power devices.

Enhancing methanol tolerance of Thermomyces lanuginosus lipase by rational design and biodiesel production through one-step feeding of methanol

The addition of a significant quantity of methanol solution during the biodiesel production results in the denaturation of lipase. To address this issue, this study proposed a novel approach to the preparation process by designing a methanol-tolerant Thermomyces lanuginosus lipase (TLL) using a computer-aided strategy. In silico prediction yielded seven mutants, out of which two mutants, E129Y and E134W, exhibited varying degrees of improved methanol tolerance and catalytic efficiency. The methanol tolerance and stability of E129Y and E134W were observed to increase by 10–30 % and 17–35 %, respectively. Additionally, E134W exhibited a 1.13-fold increase in catalytic efficiency compared to the wild type TLL, while E129Y showed a reduction of 12.05 %. Following a one-shot addition of methanol (molar ratio of 3:1 methanol to Cornus wilsoniana oil) for 72 h in the transesterification reaction, the yields of fatty acid methyl ester (FAME) for E129Y and E134W were 69 % and 85 %, respectively, with the yield of E134W increasing by 22 %. Structural analysis indicated that the E129Y mutation formed a single hydrogen bonding interaction, while E134W produced hydrophobic interactions with neighboring amino acids, thereby augmenting the structural stability of the mutations under high methanol concentration. This study has the potential to advance the commercialization of lipases in the biodiesel production industry.

Regulating the Electronic Synergy of Asymmetric Atomic Fe Sites with Adjacent Defects for Boosting Activity and Durability toward Oxygen Reduction

AbstractThe oxygen reduction reaction (ORR) plays a fundamental role in sustainable energy technologies. However, the creation of non‐precious metal electrocatalysts with high ORR activity and durability under all pH conditions is of great significance but remains challenging. Herein, the aim is to overcome this challenge by creating a Fe single atom catalyst on a 2D defect‐containing nitrogen‐doped carbon support (Fe1/DNC) via a microenvironment engineering strategy. Microkinetic modeling reveals that FeN4(OH) moieties are the real active sites under reaction conditions. Due to the synergistic promotion effect of denser accessible FeN4(OH) moieties and defect‐induced electronic properties, Fe1/DNC catalyst achieves extraordinary ORR activity under alkaline, acidic, and neutral conditions, with half‐wave potentials of 0.95, 0.82, and 0.70 V, respectively. Moreover, a negligible performance decay is observed with this Fe catalyst in stability and methanol tolerance tests. Zn‐air battery employing Fe1/DNC delivers remarkable peak power density and long‐term operational durability. Theoretical analysis provides compelling evidence that the defects adjacent to FeN4(OH) moieties can endow an inductive effect to reshape electronic properties to balance the OOH* formation and OH* reduction. This work offers insight into the regulation of asymmetric coordination structure and electronic properties of metal sites for boosting electrocatalytic activity and stability.

Renewable lignin-derived heteroatom-doped porous carbon nanosheets as an efficient oxygen reduction catalyst for rechargeable zinc-air batteries

Lignin upgrading to various functional products is promising to realize high-value utilization of low-cost and renewable biomass waste, but is still in its infancy. Herein, using industry waste lignosulfonate as the biomass-based carbon source and urea as the dopant, we constructed a heteroatom-doped porous carbon nanosheet structure by a simple NaCl template-assisted pyrolytic strategy. Through the synergistic effect of the NaCl template and urea, the optimized lignin-derived porous carbon catalyst with high content of active nitrogen species and large specific surface area can be obtained. As a result, the fabricated catalysts exhibited excellent electrocatalytic oxygen reduction activity, as well as good methanol tolerance and stability, comparable to that of commercial Pt/C. Moreover, rechargeable Zn-air batteries assembled with this electrocatalyst have a peak power density of up to 150 mW cm-2 and prominent long-term cycling stability. This study offers an inexpensive and efficient way for the massive production of highly active metal-free catalysts from the plentiful, inexpensive and environmentally friendly lignin, offering a good direction for biomass waste recycling and utilization.

Chitosan-covered spherical natural graphite: A perfect carbon source for efficient non-PGM catalysts for electrocatalysis

Developing non-precious metal catalysts to replace Pt-based catalysts for oxygen reduction reaction (ORR) is a hotspot presently, and transition metal-nitrogen co-doped carbon (TMNC) materials have been deemed as the most promising candidates. In this work, chitosan-derived-curved-carbon covered natural spherical graphite (SG) with a well-defined core-shell structure were prepared via hydrothermal carbonization (HTC) process followed by activation under NH3 atmosphere. A series of active transition metals (M=Fe, Co, Mn) and nitrogen atom were embedded into the curved carbon to form various MNC moieties on SG surface as active sites for ORR. Among the atomic precise MNC@NSG hybrid catalysts, the FeNC@NSG shows the best ORR performance and the half-wave potential is 0.95 V (vs. RHE), which are 108 % as high as that obtained by commercial Pt/C in alkaline environment. Besides, the electrochemical stability and methanol tolerance of the catalyst is also superior to commercial Pt/C. DFT calculations reveals that the high-performance stems from the curved FeNC units in the shell and high electrical conductivity of natural SG in the core for the typical core-shell structures. Moreover, the sluggish ORR kinetics can be efficiently accelerated by the increased FeN bond length, more positive-shifted d-band center and more positive surface charge of active Fe atoms in the curved FeNC units on spherical SG. This provides an enlightenment for developing efficient non-platinum group metal (PGM) catalysts using cheap and volume natural spherical graphite as building brick for energy storage and conversion devices.

Exploring the Potential of α-MnO<sub>2</sub>/ Carbon Nanotubes for Improved Oxygen Reduction Reaction Performance at the Cathode of Alkaline Fuel Cells

In the field of fuel cell technology, the development of cost-effective catalysts is crucial for the commercialization of Alkaline Membrane Fuel Cells (AMFCs). Platinum (Pt) has traditionally been employed as the catalyst in AMFCs, but its high cost poses a major barrier to widespread adoption. In this study, a new catalyst material was developed by incorporating Manganese Dioxide (α-MnO2) into Carbon Nanotubes (CNTs) using hydrothermal synthesis techniques. The synthesized catalyst was characterized using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD), and its electrocatalytic activity was evaluated through Linear Sweep Voltammetry (LSV) and CV through Rotating Disc Electrode (RDE) experiments. The results showed that the α-MnO2-CNT composite displayed strong durability in the alkaline environment and high electrocatalytic activity for oxygen reduction reaction (ORR). The LSV measurements revealed a current density of -4.1 mA/cm2 and an overpotential of -0.3V relative to Standard Calomel Electrode (SCE) in a 0.1M KOH electrolyte. Additionally, the α-MnO2-CNT composite displayed high methanol tolerance and long-term stability compared to commercial Pt/C catalysts. This study demonstrates that the use of α-MnO2-CNT as a cost-effective alternative to Pt has the potential to facilitate the commercialization of AMFC technology.

Quasi‐in situ Observation of MnO2Nanorods by Electrochemical Transmission Electron Microscopy for Oxygen Reduction Reaction Process

Understanding the electrode materials’ surface is of fundamental importance for catalytic studies as most electrochemical reactions take place there. Although several operando techniques have been used to monitor the electrocatalytic process, real‐time imaging techniques for observing the surface change on electrode materials are still a challenge and limited to a few stable catalytic systems. Herein, the quasi‐in situ electrochemical transmission electron microscopy (TEM) was carried out to track the morphological and local structure evolution during the oxygen reduction reaction (ORR) on manganese dioxide (MnO2) for the first time. The α‐MnO2nanorods exhibit comparable ORR electrocatalytic activity (half‐wave potential,E1/2: 0.83 vs. 0.85 V vs. RHE; diffusion‐limiting current density,Jd: −5.46 vs. −5.52 mA cm−2) and better methanol tolerance than Pt/C. An electrochemical TEM chip assembled with a three‐electrode system was used to perform the electrochemical experiments similar to typical testing procedures. The ex situ and quasi‐in situ TEM images consistently showed that MnO2nanorods had undergone surface roughening, and lattice expansion with 0.97% and 1.97% in theaandc‐axis, respectively as ORR proceeded. The quasi‐in situ electrochemical TEM fills the gap between ex situ characterization and operando spectroscopies and deepens the mechanistic understanding of electrocatalytic processes.

Biomass-derived nitrogen-doped carbons activated by zinc halides for electrocatalytic oxygen reduction reaction

Biomass-derived carbon materials are certified to be excellent catalysts for oxygen reduction reaction (ORR) and their ORR activity is severely affected by activators. For this reason, three zinc halides (ZnF2, ZnBr2, and ZnI2) and ZnCl2 used as activators for the formation of pea pod-derived carbon materials are systematically investigated for the first time. The presence of ZnX2 significantly changes the morphology of biomass-derived carbon materials and effectively increases the specific surface area, surface defect and doping content of N. These factors effectively promote the ORR activity of the product, especially PPBrNC. The four resulted carbons show high onset potential, half-wave potential and limiting current density that is comparable with Pt/C, and the obvious 4-electron reduction pathway is displayed in ORR process. Meanwhile, the ultra-high stability and methanol tolerance make it a potential non-precious metal catalyst. Therefore, ZnX2 is a class of low-cost and excellent chemical activators for the preparation of biomass-derived carbon materials and can provide a new idea for exploring low-cost, efficient and stable ORR catalysts.

Development of Dual N, S‐Heteroatom Doped Hollow Carbon Spheres as an Alternative Electrocatalyst for Oxygen Reduction Reaction in Alkaline Medium

AbstractHollow heteroatom‐doped mesoporous carbons were found to be an efficient non‐noble metal catalyst to enhance the oxygen reduction reaction (ORR) in fuel cells. Here, we use dopamine hydrochloride (DHC) and dibenzyl disulfide (DBS) as the nitrogen and sulfur precursors to infiltrate N and S into the HCS in a single‐step process. Dibenzyl disulfide is less explored in literature as a sulfur dopant. Due to its high sulfur content and high boiling point, dibenzyl disulfide acts as an excellent sulfur dopant and can withstand the carbonization process. Among them, NSMHCS‐0.2 obtained by adding 0.2 g of dibenzyl disulfide at 31 h intervals to the polydopamine (PDA) loaded silica leads to the ideal N, S dual hetero‐atom doping in NSMHCS. Notably, it has a high shell thickness (45 nm), high BET surface area (637 m2 g−1), high pyridinic nitrogen (13.54 %), and thiophene sulfur (89.8 %) concentration. Such property tuning paved the way to reach a high positive onset potential (0.86 V vs RHE) and a limiting current density of 3.64 mA cm−2 at 0.4 V vs RHE. Additionally, NSMHCS‐0.2 has shown superior methanol tolerance and strong electrochemical stability when compared to Pt/C 20 %.

Preparation of Co[sbnd]N co-doped carbon nanosheets electrocatalyst for efficient oxygen reduction reaction in zinc-air battery

It is very vital that there be a high-activity and serviceable catalyst for the oxygen reduction reaction (ORR) in the Zn-air Battery. Herein, utilizing g-C3N4 as a self-sacrifice template and Cobalt-His framework as the precursor, a simple strategy was developed to synthesize Co/N co-doped carbon nanosheets (CoNC 800) as a metal electrocatalyst for ORR. Due to the Co/N co-doped CoNX site and large specific surface area, the acquired materials show a preeminent ORR catalytic activity with an initial potential (~0.96 V) and half-wave potential (E1/2) of 0.85 V (vs. RHE) in an alkaline medium. Most importantly, the material has superior long-term stability and methanol tolerance than Pt/C. Furthermore, we assembled the Zn-air battery employing catalyst as an air cathode catalyst, demonstrating maximum power densities of 144 mWcm−2, a specific capacity of 821.50 Wh·kg−1, and charge/discharge cycle stability of more than 140 h. The nanosheet structure electrocatalysts derived from the Cobalt-His framework and g-C3N4 provide an innovative and instructive approach to the design of diverse nanomaterials.

Metal-organic-framework-derived Fe, Co, N-tri-dopped porous carbon as oxygen electrocatalysts for Zn-air batteries

To commercialize the rechargeable zinc-air (Zn-air) battery, it is desirable but challenging to design highly active, low-cost, stable, and earth-rich bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) to replace rare, expensive, and unstable noble-metal electrocatalysts. Herein, two MOFs are combined under electrostatic interaction and pressure by the way of Ball milling. Then, after post-processing including calcination, acid pickling, and N doping, the bimetal (Fe and Co) and N triple-doped porous carbon electrocatalyst (MIL/ZIF-4-700 °C-NH3) is prepared. Noteworthily, the MIL/ZIF-4-700 °C-NH3 has bimetallic active sites, high contents of pyridine N and graphite N, large surface area, mesoporous structure, and conductive carbon skeletons, which decide the excellent ORR performance. For ORR, the half-wave potential (E1/2 = 0.902 V vs. RHE) of MIL/ZIF-4-700 °C-NH3 is 27 mV higher than that of 20 wt% Pt/C (E1/2 = 0.875 vs. RHE). And the catalyst has also excellent methanol tolerance and stability. The Zn-air battery with MIL/ZIF-4-700 °C-NH3 as cathode catalyst has higher peak power density (176.5 mW cm−2) than that with 20 wt% Pt/C (141.8 mW cm−2) and 20 wt% Pt/C + RuO2 (94.4 mW cm−2) as cathode catalyst. Meanwhile, the Zn-air battery with MIL/ZIF-4-700 °C-NH3 as cathode catalyst exhibits perfect charge-discharge stability (longer than 540 h).

Substituent effect in determining the total structure of an all-alkynyl-protected Ag98 nanocluster for methanol tolerant oxygen reduction reaction.

Metal nanoclusters (NCs) with atomically precise structures are desirable models for truly understanding their structure-property relationship. This study reports the synthesis and structural anatomy of a Ag98 NC protected solely by an alkynyl ligand, 2-(trifluoromethyl)phenylacetylene (2-CF3PhC[triple bond, length as m-dash]CH), which features a -CF3 substituent at the ortho position (ortho-CF3). 2-CF3PhC[triple bond, length as m-dash]CH ligands are so exquisitely arranged on the surface of Ag98 that the steric hindrance caused by ortho-CF3 is minimized but its function as a hydrogen-bond (H-bond) acceptor (H⋯F) is maximized. Such a rule also applies to inter-cluster interactions which define the stacking sequence of Ag98 NCs. When supported on carbon black, Ag98 NCs demonstrate desirable oxygen reduction activity with robust long-term durability and excellent methanol tolerance, outperforming the commercial Pt/C catalyst.