Vincent Artero

Owing to its large earth crust abundance, long‐term stability, and high intrinsic conductivity, molybdenum sulfide (MoS ₂ ) has emerged as a promising hydrogen evolution reaction (HER) electrocatalyst. However, the key challenge for the HER is to activate the broader inert basal plane of MoS ₂ to increase the density of active sites and maximize catalytic activity. Heteroatom doping can open sulfur vacancies and produce defects that create additional active sites. Herein, we demonstrate for the first time a trimetallic W‐ and V‐doped MoS ₂ nanocatalyst synthesized with different doping ratios by a green synthesis route. W and V dopants induce a synergistic effect on the nanoflower‐shaped MoS ₂ structure, increasing the density of defects in the MoS ₂ 2D layer as well as in layer stacking. We show a correlation between defect density, increased number of exposed edge sites, enhanced active surface area, and better electrocatalytic activity in this series of materials. The best W and V codoped MoS ₂ electrocatalyst exhibits an overpotential of 186 mV at 10 mA·cm ⁻² for HER, which is 1.2 times lower than that of pristine MoS ₂ , and delivers hydrogen production with 100% Faradaic efficiency in continuous operation for over 16 h.

Direct comparisons between homogeneous and heterogeneous electrocatalysis using the same molecular system remain rare, despite their importance for catalyst design and device integration. Here, we investigate the heterogenization of the DuBois–Shaw nickel catalyst [Ni(PCy2NArg2)2]2+ (NiCyArg), a well-characterized molecular electrocatalyst for reversible H2/H+ interconversion, and assess whether its established homogeneous mechanistic framework can be extended to surface-confined conditions. The catalyst was successfully immobilized onto edge-plane graphite electrodes via noncovalent interactions. Cyclic voltammetry over a range of pH values under Ar and H2 demonstrates that the heterogenized catalyst retains its reversibility and bidirectional catalytic activity near the thermodynamic H2/H+ potential, with a pronounced bias toward hydrogen oxidation. Pourbaix analysis reveals redox potentials and pKa values of key intermediates that closely match those obtained under homogeneous conditions, indicating minimal perturbation of the thermodynamic landscape upon immobilization. Kinetic analysis using a simplified ECrECr model shows that the same chemical step remains rate-limiting in both regimes, while internal proton-transfer processes are modestly slowed upon surface confinement. Overall, this work provides a quantitative bridge between homogeneous and heterogeneous systems and demonstrates that solution-phase mechanistic models can in some conditions be applied to surface-immobilized systems.

Direct comparisons between homogeneous and heterogeneous electrocatalysis using the same molecular system remain rare, despite their importance for catalyst design and device integration. Here, we investigate the heterogenization of the DuBois–Shaw nickel catalyst [Ni(P ^Cy ₂N ^Arg ₂) ₂ ] ² ⁺ (NiCyArg), a well-characterized molecular electrocatalyst for reversible H₂/H⁺ interconversion, and assess whether its established homogeneous mechanistic framework can be extended to surface-confined conditions. The catalyst was successfully immobilized onto edge-plane graphite electrodes via noncovalent interactions. Cyclic voltammetry over a range of pH values under Ar and H₂ demonstrates that the heterogenized catalyst retains its reversibility and bidirectional catalytic activity near the thermodynamic H₂/H⁺ potential, with a pronounced bias toward hydrogen oxidation. Pourbaix analysis reveals redox potentials and p K ₐ values of key intermediates that closely match those obtained under homogeneous conditions, indicating minimal perturbation of the thermodynamic landscape upon immobilization. Kinetic analysis using a simplified ECrECr model shows that the same chemical step remains rate-limiting in both regimes, while internal proton transfer processes are modestly slowed upon surface confinement. Overall, this work provides a quantitative bridge between homogeneous and heterogeneous systems and demonstrates that solution phase mechanistic models can in some conditions be applied to surface immobilised systems.

Direct comparisons between homogeneous and heterogeneous electrocatalysis using the same molecular system remain rare, despite their importance for catalyst design and device integration. Here, we investigate the heterogenization of the DuBois–Shaw nickel catalyst [Ni(P ^Cy ₂N ^Arg ₂) ₂ ] ² ⁺ (NiCyArg), a well-characterized molecular electrocatalyst for reversible H₂/H⁺ interconversion, and assess whether its established homogeneous mechanistic framework can be extended to surface-confined conditions. The catalyst was successfully immobilized onto edge-plane graphite electrodes via noncovalent interactions. Cyclic voltammetry over a range of pH values under Ar and H₂ demonstrates that the heterogenized catalyst retains its reversibility and bidirectional catalytic activity near the thermodynamic H₂/H⁺ potential, with a pronounced bias toward hydrogen oxidation. Pourbaix analysis reveals redox potentials and p K ₐ values of key intermediates that closely match those obtained under homogeneous conditions, indicating minimal perturbation of the thermodynamic landscape upon immobilization. Kinetic analysis using a simplified ECrECr model shows that the same chemical step remains rate-limiting in both regimes, while internal proton transfer processes are modestly slowed upon surface confinement. Overall, this work provides a quantitative bridge between homogeneous and heterogeneous systems and demonstrates that solution phase mechanistic models can in some conditions be applied to surface immobilised systems.

Cathodes functionalised using molecular catalysts represent a promising approach for the efficient conversion of CO₂ into valuable products, with the potential to meet the performance metrics relevant to industrial applications. However, assessing the intrinsic activity of the metal centre while maintaining stability of the catalysts molecular scaffold during electrolysis still remains a challenge. This work focuses on the in-depth characterisation of a tetraaza-macrocyclic cobalt complex-based molecular cathode, from gaining a more accurate description of the catalysts performance metrics to the investigation of its probable deactivation pathway during electrocatalytic CO2 reduction (CO2RR). Importantly, our findings confirm that lowering the surface concentration of the catalysts allows to reach a catalytic regime where the activity is not anymore limited by mass transport within the porous multiwalled carbon nanotubes film but by the intrinsic activity of the immobilised catalyst, therefore allowing to determine its TOFmax value of 4.9 s-1. We propose that at least two populations of catalysts are present at the electrode surface, with variable contribution to the electrocatalytic process. Post operando studies provide key insights on the deactivation process of the immobilised catalyst via hydrogenation of both imine functions followed by demetallation.

Among the large family of mononuclear bis-diphosphine nickel catalysts with pendant amines, the so-called NiCyArg complex, with a cyclohexyl group at the phosphine and an arginine substituted amine, has attracted attention for catalyzing H₂ oxidation and production reversibly in aqueous solutions, with a significant bias in favor of H₂ oxidation. Here, we analyze the voltammetric responses of this complex and an analogue where the cyclohexyl group was replaced with a phenyl group. Our analysis helps distinguish the molecular and kinetic distinct determinants of rate, directionality and reversibility of NiP₂N₂ redox molecular catalysts of H⁺/H₂ conversion. The NiPhArg complex described in this work is a bidirectional, reversible catalyst over a large range of pH. It is strongly biased in the direction of reductive catalysis, and still active for proton reduction at pH 9. It could become useful in applications where H₂ evolution should be catalyzed in aqueous solutions under mild conditions and at low overpotential.

This study reports the synthesis, electrochemical characterization, and photophysical properties of two novel photoactive polyoxometalate (POM)–Ir photosensitizer hybrid assemblies. Under visible light irradiation in the presence of triethylamine and trifluoroacetic acid, the polyoxomolybdate-based dyad photoaccumulates the electrons via an efficient intramolecular photoinduced electron transfer process.

To solve both the greenhouse effect and energy crisis issues, direct capture and conversion of CO₂ appears as a promising contribution. Artificial photosynthesis is an encouraging and very attractive complementary way to convert CO₂ into high‐value‐added chemicals. Nevertheless, efficient CO₂ conversion remains challenging, mainly due to the poor CO₂ adsorption_, the high activation energy required to break C═O bonds, and the slow dynamics of charge carriers in light‐harvesting materials. In recent years, some Metal‐organic frameworks (MOFs) have emerged in the photocatalysis field, especially due to their huge CO₂ adsorption capability and light‐harvesting properties behavior. In this study, a series of defective NH₂‐UiO‐66 MOF materials, using formic acid (FA) is synthesized as a modulating agent. Then, a series of binary (MOF/TiO₂) catalysts is obtained by varying the defective MOFs content, followed by further deposition of gold (Au) nanoparticles (NPs) to result in three‐component MOF/TiO₂/Au composites. These composites are assessed for gas‐phase CO₂ photoreduction in the presence of water vapor as the only reducing agent. This hybrid ternary photocatalyst not only increases CO₂ adsorption but also promotes CH₄ formation. Among these resulting MOF/TiO₂/Au samples, the optimized photocatalytic activity results in a mean production rate of 17.2 µmol.h⁻¹.g⁻¹_catalyst of CH₄, which is 6‐fold higher than the one observed for the reference TiO₂/Au photocatalyst.

The active sites of metalloenzymes involved in small molecules activation often contain pendant bases that act as proton relay promoting proton‐coupled electron‐transfer processes. Here we focus on hydrogenases and on the reactions they catalyze, i. e. the hydrogen evolution and oxidation reactions. After a short description of these enzymes, we review some of the various biomimetic and bioinspired molecular systems that contain proton relays. We then provide the formal electrochemical framework required to decipher the key role of such proton relay to enhance catalysis in a single direction and discuss the few systems active for H₂ evolution for which quantitative kinetic data are available. We finally highlight key parameters required to reach bidirectional catalysis (both hydrogen evolution and hydrogen oxidation catalyzed) and then transition to reversible catalysis (both reactions catalyzed in a narrow potential range) as well as illustrate these features on few systems from the literature.

The active sites of metalloenzymes involved in small molecules activation often contain pendant bases that act as proton relay promoting proton‐coupled electron‐transfer processes. Here we focus on hydrogenases and on the reactions they catalyze, i. e. the hydrogen evolution and oxidation reactions. After a short description of these enzymes, we review some of the various biomimetic and bioinspired molecular systems that contain proton relays. We then provide the formal electrochemical framework required to decipher the key role of such proton relay to enhance catalysis in a single direction and discuss the few systems active for H ₂ evolution for which quantitative kinetic data are available. We finally highlight key parameters required to reach bidirectional catalysis (both hydrogen evolution and hydrogen oxidation catalyzed) and then transition to reversible catalysis (both reactions catalyzed in a narrow potential range) as well as illustrate these features on few systems from the literature.