Kotaro Takeyasu

Cooperative pyridinic-N (pyri-NH) and pyrrolic-N (pyrr-NH) sites in N-doped nanographene drive selective 2e ⁻ ORR. Carbon adjacent to the –pyri-NH activates O ₂ and proton transfer (pyri-NH → pyrr-NH) for efficient OOH formation and H ₂ O ₂ release.

Acidic oxygen reduction is often discussed as if catalytic activation and mass transport were inseparable. Here, biomass‐derived carbon was used to examine these contributions through oxidation, ammonia annealing, and KOH activation. The onset potential is associated primarily with defect‐derived p _z / π electronic states, whereas the maximum slope in the transport‐influenced region is associated with hierarchical pore accessibility and connectivity. Apparent electrochemically accessible surface area does not correlate significantly with onset potential in the six‐sample series, although it covaries with maximum slope; this covariance is attributed to pore accessibility rather than surface area itself. Multiscale X‐ray tomography of the optimized catalyst visualizes connected pore pathways from macro‐ to submicrometer scales, while the connected framework may be partly inherited from the rice‐husk precursor. The combined results support preferentially separate consideration of electronic activation and pore‐network accessibility for the acidic oxygen reduction reaction.

Designing efficient and durable carbon-based electrocatalysts remains a major challenge for next-generation energy technologies. Here, we introduce a comprehensive nanoarchitectonics approach for constructing metal-organic framework on fullerene (MOFOF) hybrids with diverse dimensionalities spanning 0D nanospheres, 1D nanorods and nanotubes, 2D sheets, and 3D cubic assemblies, and demonstrate their potential for electrocatalyst development through the pyrolysis of a selected hybrid. Through a sequential layer-by-layer (or, step-by-step) growth of a typical MOF (ZIF-67) on self-assembled fullerene supports, we generated a family of MOFOF nanostructures with diverse morphologies. Subsequent high-temperature carbonization and ammonia-assisted nitrogen doping are expected to transform these MOFOF precursors into hierarchical nitrogen-doped Co/C electrocatalysts featuring well-defined Co-N_x active sites embedded within graphitized carbon frameworks. Using quasi-1D fullerene nanotubes (FNTs) as a structural template produced the most efficient catalyst, Co-N@CT-900, which delivered an onset potential of 0.78 V vs RHE and a Tafel slope of 56.6 mV dec^-1, along with excellent electrochemical durability, retaining 95.2% of its initial current over 42,000 s in acidic electrolyte. More importantly, RRDE analysis revealed high H₂O₂ selectivity exceeding 70%, indicating that the catalyst preferentially promotes the two-electron oxygen reduction pathway. Despite efficient peroxide generation, Co-N@CT-900 maintained superior stability compared to reference catalysts, highlighting its resistance to oxidative degradation. The superior performance arises from the synergistic integration of Co-supported active sites and protective graphitic carbon shells, which enable efficient H₂O₂ production while preserving structural integrity under acidic conditions. These findings position Co-N@CT-900 as a promising high-durability catalyst for advanced water treatment technologies based on in situ H₂O₂ generation.

Protonation of pyridinic nitrogen (pyri‐N) sites in nitrogen‐doped carbon catalysts under acidic conditions converts pyri‐N to pyri‐NH ⁺ , leading to severe catalytic deactivation. Restoring activity requires transforming pyri‐NH ⁺ back to pyri‐NH, an energetically demanding process that limits oxygen reduction reaction (ORR) efficiency. To overcome this challenge, we developed an N‐doped porous carbon catalyst (NpC‐7) featuring surface pyri‐N active sites and a subsurface graphitic nitrogen (grap‐N) layer. The 2D growth of cyanuric acid (CA)‐functionalized 2‐hydroxyethyl methacrylate (HEMA) polymer within graphene oxide layers ensures uniform N‐doping which modulates π‐electron and spin states. This engineered architecture delivers ORR activity approaching Pt/C and surpasses conventional nitrogen doped graphene oxide (NrGO) ( E _onset = 0.86 V, E _1/2 = 0.70 V vs. 0.76 and 0.61 V, respectively). Enhanced performance arises from subsurface grap‐N, which donates electron to protonated pyri‐NH ⁺ , generating an active pyri − NH ^{δ +} state that promotes O ₂ adsorption. In situ electrochemical Raman spectroscopy and density functional theory (DFT) calculations confirm efficient O ₂ adsorption and intermediate formation, indicating a (2 + 2)e ⁻ ORR pathway. These findings highlight the critical role of subsurface grap‐N in overcoming acidic deactivation through electronic modulation, offering a blueprint for designing acid‐stable carbon electrocatalysts.

Understanding how chemical energy dissipates as heat in non-equilibrium redox systems is a fundamental problem in physical chemistry.

Understanding how chirality emerges from assemblies of achiral molecules is central to the study of symmetry breaking at surfaces. Here we show that achiral 1,10‐phenanthroline adsorbed on Au(111) generates chirality through a pairing‐driven hierarchical self‐assembly pathway. Upon adsorption, molecules selectively form hydrogen‐bonded pairs via weak but directional C─H···N interactions. Steric and electrostatic constraints restrict this interaction to two molecules, forcing a choice between two symmetry‐equivalent nitrogen sites and thereby producing left‐ or right‐handed molecular pairs that act as local chiral motifs. These motifs organize through attractive intermolecular interactions into homochiral one‐dimensional chains, which further assemble into two‐dimensional chiral domains governed by repulsive interchain interactions. Scanning tunneling microscopy directly visualizes mirror‐related left‐ and right‐handed domains. Density functional theory calculations confirm that the face‐to‐face paired configuration is energetically preferred and stabilized by adsorption on Au(111). This work reveals a distinct route to surface chirality in which chirality originates at the level of a hydrogen‐bonded molecular pair and is amplified into organized chiral architectures through weak intermolecular interactions.

The valence state and 3D structure of vacuum-deposited Cu species on α-Al ₂ O ₃ (0001) surface have been determined using the PTRF-XAFS technique and DFT calculations.

Designing oxygen evolution reaction (OER) electrocatalysts that can reversibly operate as both oxidation and reduction electrodes is key to developing efficient and rechargeable electrochemical energy systems. However, the evolution of nickel active sites between hydroxide and oxyhydroxide phases, and how such transformations can be made reversible under dynamic operating conditions, remains poorly understood. Here, we report a sulfuric‐acid‐induced surface oxidation strategy that enables both the controlled formation and reversible regeneration of β‐NiOOH active sites on free‐standing nickel foam electrodes. Moderate H ₂ SO ₄ treatment (1 M) produces an optimized electrode (1.0‐Ni) exhibiting superior OER performance, requiring overpotentials ( η ) of only 218, 348, and 458 mV at 10, 500, and 1000 mA cm ^{− 2} , respectively. The enhanced activity originates from sulfuric‐acid‐induced modulation of Ni sites, which promotes β‐NiOOH formation as the catalytically active phase while maintaining structural integrity. Moreover, a buried β‐NiOOH‐rich layer serves as a structural‐memory reservoir, allowing reversible reconstruction of surface β‐NiOOH during redox cycling. This reversible behavior enables the same electrode to function as both anode and cathode, relevant to rechargeable zinc–air battery and other bifunctional electrochemical systems. The dual mechanism acid‐induced active‐site formation and electrochemical regeneration thus provides a scalable strategy for constructing reversible, heteroatom‐free nickel electrodes for sustainable energy conversion.

Ethanol synthesis from CO ₂ and H ₂ is currently a hot topic of research in heterogeneous catalysis. However, the underlying mechanism has not yet been clearly elucidated. We propose that the synthesis involves several other reactions on the electrode surface, as evident by the formation of a mixed potential. In this study, we prepared solid catalysts, Ru/CoO _x and CuPd/C, as the nano‐anode and nano‐cathode components and carried out CO ₂ hydrogenation in the presence of small amounts of water to facilitate ion conduction. Ethanol was produced along with CO, CH ₄ , and methanol at reaction temperatures below 473 K in the presence of both the catalysts. The activation energy for ethanol formation with Ru/CoO _x was found to be 25 ± 5 kJ mol ⁻¹ , which was much lower than those for the formations of CO (44 ± 4 kJ mol ⁻¹ ), CH ₄ (77 ± 7 kJ mol ⁻¹ ), and methanol (81 ± 9 kJ mol ⁻¹ ). In addition, the production of CO was promoted by the encapsulated water. These results also suggest a mixed‐potential‐driven mechanism for the synthesis of ethanol.