Janis Timoshenko

Cu( i ) mobility in chabazite is tracked by combining XAS and DFT.

Integrating cobalt nitrogen heterojunctions in cobalt phosphide as an enhanced bifunctional electrocatalyst.

Here supervised machine learning guides the disentanglement of contributions of multiple coexisting species to the sample-averaged spectroscopic data, by recognizing common patterns in large datasets of spectra for a broad range of compounds.

The electrosynthesis of amino acids represents a fascinating and promising frontier in green chemistry, offering a sustainable alternative to conventional industrial processes such as the energy-intensive Strecker synthesis through the adoption of efficient, electricity-driven methods. Herein, Sn is identified as an effective catalyst for glycine electrosynthesis using concentrated nitric acid and oxalic acid as feedstocks, and we investigate the reaction mechanism at industrial-level current rate (1 A cm ^-2 ). In-situ characterization reveals that the Sn undergoes dynamic valence cycle and reconstructs into amorphous-Sn under acidic conditions. At high current, the change in local pH promotes the anionic states of oxalic acid and C-intermediates, which enhances the adsorption of key intermediates such as glyoxalic acid and acid oxime. This switches the mechanism from a chain reaction to an interfacial hydrogenation, thereby increasing the rate of glycine formation. By increasing the dominance of interfacial reaction versus the chain reaction, we achieve a glycine Faradaic efficiency of 93%, and industrial-level partial current density of 0.9 A cm ⁻² in a flow cell.

Electrosynthesis of amino acids is a novel and promising green synthetic strategy. However, the lack of efficient catalysts limits catalytic performance, in terms of reaction rate and Faradaic efficiency. Here, Sn is identified as an effective catalyst for glycine electrosynthesis using concentrated nitric acid and oxalic acid as feedstocks, and we investigated the reaction mechanism at industrial-level cur-rent rate (1 A cm-2). In-situ characterization (XRD, Raman spectroscopy, XAS, etc.) revealed that the Sn undergoes dynamic valence cycle and reconstructs into amorphous-Sn under acidic conditions. At high current, the change in local pH promotes the anionic states of oxalic acid and C-intermediates, which enhances the adsorption of key intermediates such as glyoxalic acid and acid oxime. This switches the mechanism from a chain reaction to an interfacial hydrogenation, thereby increasing the rate of glycine formation. By increasing the dominance of interfacial reaction versus the chain reac-tion, we achieved a glycine FE of 93%, and industrial-level patrial current density of 0.9 A cm−2 in a flow cell.

Growing environmental concerns have led to a need for the reduction of CO₂ emissions and the search for alternative fuels. The synthesis of methanol via the CO₂ hydrogenation reaction provides a promising approach for these tasks. Promoting the existing Cu-based catalysts with Ga might be an option to create more effective catalysts. Here, size-controlled bimetallic CuGa nanoparticles (NPs) supported on either SiO₂ or ZnO were synthesized to study the nature of the interaction of Cu and Ga. Operando spectroscopy and diffraction characterization methods (XPS, XAS, XRD) were employed to establish structure, chemical composition, and reactivity correlations. We find that Ga stays oxidized under the reaction conditions and segregates to the surface. For the CuGa NPs/ZnO, the dominating interaction of Cu with ZnO inhibits the promoting effect of Ga. Only on the inert SiO₂ support, the beneficial influence of Ga is visible. Furthermore, high pretreatment temperatures were found to result in a favorable Cu–Ga interaction by partially reducing Ga, which is beneficial for methanol selectivity.

The sluggish kinetics of the oxygen evolution reaction are an energetic bottleneck for green hydrogen production via water electrolysis. The reaction proceeds over a surface that undergoes (frustrated) phase transitions to accommodate bias-dependent excess charge. Here we perform Arrhenius analysis of common catalysts and correlate the activation energy and pre-exponential factor with the oxide’s structural adaptation via operando X-ray absorption spectroscopy and high-energy X-ray diffraction. We observe that the kinetics switch from a regime that is probably dominated by interfacial solvation to one where the surface energetics take over. This happens right at a transition potential between the α or β phases into the γ-crystal structure of Ni (oxy)hydroxides and when spectroscopic fingerprints of key intermediates emerge. Importantly, this turning potential is independent of the loading or the surface area and informs on the intrinsic catalyst activity. These results suggest that the catalyst activity is intrinsically linked to the initial interfacial solvation (pre-)step.

Subjecting copper to short anodic pulses during the electrocatalytic reduction of carbon dioxide (CO₂RR) has been shown to improve the activity and selectivity towards hydrocarbons and alcohols. Nonetheless, the nature of the active sites is still unclear. Here the evolution of the morphology, chemical state and crystal structure of Cu(100) exposed to potential pulses during the CO₂RR was resolved by a combination of spectroscopy, microscopy and diffraction methods applied concurrently. Under anodic potential pulses, (n10) facets were formed. Moreover, alternating anodic to cathodic potential pulses during the CO₂RR also lead to the stabilization of copper oxide species located either at the surface or directly underneath ultrathin metallic copper layers, depending on the specific pulse potential treatment applied. Both findings are key for the enhanced ethylene and ethanol production reported during pulsed CO₂RR.

Pulsed electrolysis attracts attention as a simple tool for tuning the structure and properties in many electrocatalytic systems. Here, pulsed reaction protocols are used to control the structure and selectivity of copper and nitrogen co‐doped carbon (Cu‐N‐C) catalysts, employed for electrocatalytic CO ₂ reduction reaction (CO ₂ RR). Specifically, while this catalyst is mostly selective for hydrogen during potentiostatic reduction, as high as 82% Faradaic efficiency for CO ₂ RR products is reached by optimizing the pulse parameters. It is found that the product distribution depends strongly on the values of both the anodic and cathodic potentials, and the pulse parameter ranges for preferential CO, CH ₄ , and C ₂ H ₄ formation were identified. By performing detailed in situ and operando spectroscopic analysis, it is found that i) pulsing creates a favorable microenvironment for CO ₂ RR by reducing the surface H‐coverage on the N‐doped carbon support, and ii) the dynamic evolution of the Cu active sites directs the selectivity toward hydrocarbons (CH ₄ , C ₂ H ₄ ). The periodic application of increasingly more anodic potentials results in more efficient redispersion of the metallic Cu clusters that are formed under cathodic potential. The C ₁ /C ₂₊ selectivity ratio depends on the fraction of the stabilized Cu single atoms and the size of the Cu particles formed under working conditions.