Platinum is an important material with applications in oxygen and hydrogen electrocatalysis. To better understand how its activity can be modulated through electrolyte effects in the double layer microenvironment, herein we investigate the effects of different acid anions on platinum for the oxygen reduction/evolution reaction (ORR/OER) and hydrogen evolution/oxidation reaction (HER/HOR) in pH 1 electrolytes. Experimentally, we see the ORR activity trend of HClO4 > HNO3 > H2SO4, and the OER activity trend of HClO4$$ > $$ > HNO3 ∼ H2SO4. HER/HOR performance is similar across all three electrolytes. Notably, we demonstrate that ORR performance can be improved 4-fold in nitric acid compared to in sulfuric acid. Assessing the potential-dependent role of relative anion competitive adsorption with density functional theory, we calculate unfavorable adsorption on Pt(111) for all the anions at HER/HOR conditions while under ORR/OER conditions $${{{{{\rm{Cl}}}}}}{{{{{{\rm{O}}}}}}}_{4}^{-}$$ Cl O 4 − binds the weakest followed by $${{{{{\rm{N}}}}}}{{{{{{\rm{O}}}}}}}_{3}^{-}$$ N O 3 − and $${{{{{\rm{S}}}}}}{{{{{{\rm{O}}}}}}}_{4}^{2-}$$ S O 4 2 − . Our combined experimental-theoretical work highlights the importance of understanding the role of anions across a large potential range and reveals nitrate-like electrolyte microenvironments as interesting possible sulfonate alternatives to mitigate the catalyst poisoning effects of polymer membranes/ionomers in electrochemical systems. These findings help inform rational design approaches to further enhance catalyst activity via microenvironment engineering.

In this work, we implement a facile microwaveassisted synthesis method to yield three binary Chevrel-Phase chalcogenides (Mo 6 X 8 ; X = S, Se, Te) and investigate the effect of increasing chalcogen electronegativity on hydrogen evolution catalytic activity. Density functional theory predictions indicate that increasing chalcogen electronegativity in these materials will yield a favorable electronic structure for proton reduction. This is confirmed experimentally via X-ray absorption spectroscopy as well as traditional electrochemical analysis. We have identified that increasing the electronegativity of X in Mo 6 X 8 increases the hydrogen adsorption strength owing to a favorable shift in the pband position as well as an increase in the Lewis basicity of the chalcogen, thereby improving hydrogen evolution reaction energetics. We find that Mo 6 S 8 exhibits the highest hydrogen evolution activity of the Mo 6 X 8 series of catalysts, requiring an overpotential of 321 mV to achieve a current density of 10 mA cm −2 ECSA , a Tafel slope of 74 mV per decade, and an exchange current density of 6.01 × 10 −4 mA cm −2 ECSA . Agreement between theory and experiment in this work indicates that the compositionally tunable Chevrel-Phase chalcogenide family is a promising framework for which electronic structure can be predictably modified to improve catalytic small-molecule reduction reactivity.

Presented herein is an investigation of a promising ternary metal sulfide catalyst that is capable of electrochemically converting CO2 to liquid and gas fuels such as methanol and hydrogen.

The Chevrel phase (CP) is a class of molybdenum chalcogenides that exhibit compelling properties for next-generation battery materials, electrocatalysts, and other energy applications. Despite their promise, CPs are underexplored, with only ∼100 compounds synthesized to date due to the challenge of identifying synthesizable phases. We present an interpretable machine-learned descriptor (H δ) that rapidly and accurately estimates decomposition enthalpy (ΔH d) to assess CP stability. To develop H δ, we first used density functional theory to compute ΔH d for 438 CP compositions. We then generated >560 000 descriptors with the new machine learning method SIFT, which provides an easy-to-use approach for developing accurate and interpretable chemical models. From a set of >200 000 compositions, we identified 48 501 CPs that H δ predicts are synthesizable based on the criterion that ΔH d < 65 meV/atom, which was obtained as a statistical boundary from 67 experimentally synthesized CPs. The set of candidate CPs includes 2307 CP tellurides, an underexplored CP subset with a predicted preference for channel site occupation by cation intercalants that is rare among CPs. We successfully synthesized five of five novel CP tellurides attempted from this set and confirmed their preference for channel site occupation. Our joint computational and experimental approach for developing and validating screening tools that enable the rapid identification of synthesizable materials within a sparse class is likely transferable to other materials families to accelerate their discovery.

State-of-the-art high temperature oxide melt solution calorimetry and density functional theory were employed to produce the first systematic study of thermodynamic stability in a series of binary and ternary Chevrel phases. Rapid microwave-assisted solid-state heating methods facilitated the nucleation of pure-phase polycrystalline M y Mo6S8 (M = Fe, Ni, Cu; y = 0, 1, 2) Chevrel phases, and a stability trend was observed wherein intercalation of M y species engenders stability that depends on both the electropositivity and ionic radii of the intercalant species. Ab initio calculations indicate that this stability trend results from competing ionic and covalent contributions, where transition metal intercalation stabilizes the Chevrel structure through increased ionicity but destabilizes the structure through reduced covalency of the Mo6S8 clusters. Our calculations predicted that over intercalation of high-valent M y species leads to slight destabilization of the Mo6 octahedral cores, which we confirm using calorimetry and X-ray absorption spectroscopy. Our combined computational and calorimetric analysis reveals the interplay of the foundational principles of ionic and covalent bonding characteristics that govern the thermodynamic stability of Chevrel and other inorganic phases.

Microwave-assisted solid-state heating has been employed to induce anisotropic nucleation of M2Mo6S6 (M = K, Rb, Cs) nanorods without a template for the first time, and interfacial charge-transport properties of these rods are evaluated.

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Transformative solutions to contemporary energy problems hinge on the successful development of non-noble functional materials. A promising avenue toward sustainable energy conversion and storage is the synthesis and integration of electrocatalyst materials with interfaces that drive small-molecule electroreduction reactions like CO2 and CO conversion to fuels, as well as hydrogen production from water. While research advances in the past several decades have led to deployable technologies on both of these fronts, industrial scalability is undercut by high material cost, lack of catalyst selectivity, and poor long-term operational stability. In this perspective, we highlight the exceptional promise of multinary chalcogenides as an expansive yet underexplored composition space where catalytic functionality and synthesizability can be predicted and finely controlled by leveraging nominal composition, dimensionality, crystallinity, and morphology. We further outline a path forward for chalcogenide material discovery that integrates theory with experiment to rationally inform material design and accelerate the synthesis of functional energy materials.