Metal-mediated nitrogen reduction offers a route to decentralised, low-carbon ammonia synthesis, but its selectivity is poorly understood and often attributed to the formation of a solid-electrolyte interphase (SEI). Here we show that ammonia selectivity in lithium-mediated nitrogen reduction is governed by the relative chemical potentials of lithium and proton carriers in the electrolyte, rather than by SEI composition. By independently tuning lithium-ion and proton-carrier chemical potentials across a range of salts, solvents and proton sources, we find that ammonia, hydrogen and unreacted lithium yields collapse onto a single descriptor defined by the difference between the Li + /Li and H + /H 2 potentials. Post-mortem analysis of electrode deposits shows that SEI formation correlates with lithium chemical potential but does not determine selectivity; instead, SEI growth primarily suppresses both N 2 reduction and H 2 evolution rates through passivation. These results explain previously observed bell-shaped selectivity trends and provide a thermodynamic framework for designing electrolytes and redox mediators for selective and energy-efficient ammonia synthesis.

In aqueous electrocatalytic environments, the protonation of stable *CO and *N2 to *COH/*CHO and *NNH is fundamentally challenged by the competing hydrogen evolution reaction (HER). In this context, direct dissociation of these molecules offers an alternative pathway, forming reactive *C or *N fragments that can be reduced further if surface bonding is not too strong. However, the strong C≡O and N≡N bonds make dissociation challenging under ambient electrochemical conditions, and the extent to which solvent, local field, and electrolyte ions can promote bond dissociation remains unclear. In this work, we quantify these dissociation path at a Co(B5) step site using density functional theory, implicit-solvent calculations, and explicit-solvent enhanced sampling with a machine-learned interatomic potential (MLIP). Implicitsolvent calculations reveal only weak sensitivity to dielectric constant, dipole moment and solvent radius, with barrier variations typically within ≤ 0.1 eV. In contrast, the local H-bonding network in explicit-solvent simulations lowers the dissociation barrier by ∼ 0.3 eV relative to vacuum by stabilising the dissociating atoms. Across different solvents and aqueous solutes, the barrier correlates qualitatively with hydrogen-bond donor strength, pKa, and the local H-coordination number near the transition-state region. Interfacial cations (Li+ and Cs+) modify the work function but do not significantly change the dissociation barrier compared with pure water, suggesting that solvent-mediated interactions dominate under the studied conditions.

The electrochemical reduction of carbon dioxide (eCO2RR) offers a promising fossil-free route for producing valuable carbon-based fuels. However, its large scale implementation is limited by the lack of a catalyst with adequate performance to economically compete with fossil-based methods. Copper, although neither sufficiently active nor selective, is widely regarded as the state-of-the-art catalyst capable of reducing CO2 into valuable multi-carbon products. In this work, we explore alternative materials to copper through applying resource-efficient and straightforward computational screening. By considering thermodynamic stability, binding energies, and work functions, we narrow down the ∼150,000 materials available on the Materials Project database to a shortlist of ten potential catalysts. Our approach avoids the need for resource-intensive DFT calculations across thousands of materials. At the same time, our analysis reveals that the theoretical design space for eCO2RR catalysts is vast, indicating substantial opportunities for further exploration beyond our current screening. This is particularly relevant given that materials resembling our candidates have thus far failed to outperform copper.

The electrochemical reduction of nitrate (NO3-) to ammonia (NH3) offers a sustainable route for nitrogen cycle remediation and decentralized NH3 production. In this work, we systematically investigated the impact of electronic structure and wettability in regulating the catalytic performance of molecular catalysts using functionalized iron phthalocyanines (FePc-R, R = NH2, COOH, CN, and t-Bu) supported on carbon nanotubes. The strongly hydrophilic FePc-NH2/CNT (electron-donating functional group-containing) catalyst achieved a maximum Faradaic efficiency of 94.1% at -0.6 VRHE and a partial current density of 83.9 mA cm-2 toward NH3 at -0.9 VRHE. In contrast, strongly hydrophilic FePc-COOH/CNT and weakly hydrophilic FePc-CN/CNT, containing electron-withdrawing functional groups, delivered a lower performance across all potentials. Density functional theory (DFT) calculations revealed that electron-donating functional groups elevate the Fe-center HOMO level, facilitating hydrogenation of NHx intermediates and enhancing turnover frequency. In situ X-ray absorption spectroscopy (XAS) confirmed that Fe-N4 coordination in FePc-NH2/CNT remains stable across all tested potentials, while electron-withdrawing functional group-containing catalysts (FePc-COOH/CNT and FePc-CN/CNT) exhibited Fe-Fe cluster formation at -0.8 and -0.7 VRHE, respectively. Furthermore, coupled mass transport and reaction modeling indicated that more hydrophilic surfaces reduce the diffusion layer thickness, promoting NO3- accessibility and NH3 formation. Together, these findings decoupled the synergistic role of electronic tuning and wettability control in governing both activity and stability, providing mechanistic design principles for molecular and heterogeneous catalysts in the reduction of electrochemical NO3- to NH3.

The electrochemical reduction of CO2 is a promising way to store renewable energy in chemical bonds and convert CO2 to value-added products. In this reaction, the role of electrolyte cations has attracted a lot of attention in the past decade. Nevertheless, computational studies still lack a standardized approach for incorporating cation effects. Here, we introduce a computational cation electrode framework that provides a consistent reference state of metal cations in density functional theory calculations. We first outline the limitations of current reference schemes and then propose a new approach that combines the cation reduction potential with an intermediate bulk state that better mimics the cation in the interface. Using this computational cation electrode framework, we evaluate how the choice of reference influences adsorption energetics across metals and discuss strategies for selecting appropriate bulk states for the computational cation electrode. This work establishes a unified protocol for modeling cation effects in the reduction of CO2 and related electrochemical reactions.

Urea synthesis through electrochemical coreduction of CO2 and nitrate offers a sustainable nitrogen fixation route. However, accurate quantification remains challenging due to nitrite interference. In this study, we develop a reliable approach for accurate urea quantification and denote it the Adaptive DAMO-TSC (A-DAMO) method, which introduces the nitrite concentration as a secondary calibration variable to eliminate false positives and improve accuracy across a broad range of urea concentrations. A full workflow and MATLAB code are provided to facilitate data processing. This study highlights significant problems of NMR-based urea quantification caused by H-bond acceptors such as nitrite. To validate A-DAMO in a practical application, synthesized and commercial ZnO were used as catalysts for electrochemical urea production. While conventional methods yielded misleading results, A-DAMO effectively corrected these inaccuracies, enabling an accurate and credible evaluation of urea synthesis performance.

The catalytic performance of the electrochemical CO2 reduction reaction (CO2RR) is highly sensitive to the electrolyte microenvironment, including ion identity, concentration, and buffering chemistry. While such electrolyte effects are well established for metallic catalysts, their mechanistic roles in porous Ni-N-C systems remain less explored. Here, we systematically investigate the influence of cation (Li+, K+, Cs+, and tetramethylammonium, TMA+) and anion (phosphate, sulfate, and bicarbonate) identity and concentration on CO2-to-CO conversion. Contrary to expectations, Cs+ does not outperform K+, whereas TMAHCO3 electrolytes exhibit a pronounced enhancement in CO2RR activity, reaching a CO partial current density of 25 mA cm-2 at -0.7 VRHE in 0.5 M solution. Electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis reveal that this activity enhancement does not directly correlate with interfacial ion-/charge-transfer or mass transport behaviors. Instead, Fourier-transform infrared (FTIR) spectroscopy shows a significant increase in bulk CO2 availability in TMAHCO3 electrolytes. Overall, these results suggest that electrolyte composition affects both interfacial properties and CO2 availability in the bulk, influencing CO2RR activity within the porous Ni-N-C catalyst system.

Metal-mediated nitrogen reduction holds promise toward carbon-neutral and decentralised ammonia. Electrolyte engineering improved selectivity and stability. However, the strategies employed span a large parameter space, impeding optimisation and fundamental understanding of the forces steering selectivity. This work unifies trends in selectivity through the relative chemical potentials of Li + and H + -carrier in solution across diverse electrolyte formulations. Electrode deposit quantifications indicate that interface chemistry (Li 2-x OH x coverage on Li 0 ) scales with chemical potentials. While utilising this scaling relation could accelerate electrolyte screening, we propose a model that refines the prevailing causal relation between interphase composition and selective N 2 reduction. We suggest that thermodynamic control over the chemical potential of protons facing exposed metal defines selective proton utilisation, while passivation by Li 2-x OHx kinetically suppresses Li corrosion rates by defining the number of sites available for reacting protons and N 2 . This approach provides design rules to-wards high rate and energy efficient electrochemical ammonia synthesis.

Abstract Nitric acid is essential in fertilizer production, yet its current industrial synthesis via the Haber-Bosch and Ostwald process accounts for 1 % of the chemical sector’s energy consumption and produces significant greenhouse gas emissions. Despite considerable efforts, previous attempts at electrochemical nitrogen oxidation have proven unsuccessful due to competition with the oxygen evolution reaction (OER) and the inherent difficulty of activating the nitrogen (N2) bond under ambient conditions. In this work, we propose a phase transition-based approach inspired by electrochemical ammonia synthesis to circumvent these challenges. The strategy is centered around the formation of a metal nitride by direct nitridation of a suitable metal, followed by an oxidation step employing molecular oxygen (O2). Li and Ca are identified as particularly promising candidates to mediate such a pathway based on reaction thermodynamics, and we show experimentally that Li nitride can indeed be oxidized to yield nitrate in the presence of O2. The proposed concept demonstrates considerable potential for direct N2 oxidation, encouraging further computational and experimental investigation.

Electrocatalysis is central to electrified energy conversion technologies, including the production of fuels and chemicals from renewable electricity. In recent years, atomistic modeling based on density functional theory (DFT) has become an indispensable tool for catalysis researchers because it can provide a molecular-level perspective into catalytic reactivity that is otherwise inaccessible to experimental measurements. Computational electrocatalysis model inputs are intended to capture fundamental understanding of the complex interfacial environment of the catalytic active site, but rely on practical approximations that can affect the reliability of insights gained from DFT. This Perspective outlines a framework for rigorous and reproducible integration of theory and experiment in heterogeneous electrocatalysis research. We discuss state-of-the-art computational methods and sources of error in model development and interpretation. We describe opportunities for validation of theoretical models and experimental interpretations as it pertains to the structure of active sites, reaction energetics, and microkinetic modeling. We provide examples to help computational researchers develop models that move beyond obtaining qualitative agreement with reactivity trends, and toward the development of rigorous mechanistic insights that can be leveraged to predict promising new catalysts or operating conditions. Rigor and reproducibility are enhanced when theory and experiment have multiple nodes of connection, which enhances the longevity and robustness of conclusions and insights about electrocatalytic reactivity.

CO2 electrolysis has emerged as a promising route to carbon-neutral fuels, but Cu-based catalysts are largely limited to producing short-chain (< C3) products. In contrast, strong *CO-binding metals that underpin thermochemical Fischer-Tropsch (FT) catalysis remain largely unexplored under electrochemical conditions. Here, we investigate Co catalyst for producing C4+ hydrocarbons in membrane electrode assembly (MEA) reactors operated at elevated temperatures (30-80 °C) and industrially relevant current densities. At 80 °C and 250 mA/cm 2 , Co produces a complex spectrum of 28 distinct C₁-C₆+ products, with hydrocarbon partial current densities increasing linearly with temperature. Density functional theory calculations reveal that direct *CO dissociation on Co remains kinetically inaccessible under these reaction conditions, pointing instead to protonation-mediated pathways in CC bond formation. Strong adsorption of unsaturated hydrocarbons leads to surface coking and progressive deactivation, which is mitigated through pulsed electrolysis. Unlike Cu, the activity and selectivity trends on Co are only weakly dependent on alkali-metal cation identity, highlighting a mechanistic regime more closely analogous to FT catalysis than to classical *CO-*CO dimerization. Together, these findings establish Co as a prototype strong *CO-binding catalyst for electrochemical long-chain hydrocarbon synthesis and provide mechanistic design principles for developing high-temperature electrochemical routes to sustainable, naphtha-range fuels.

Li-mediated ammonia synthesis is – thus far – the only electrochemical method to decentralised ammonia production, an alternative to one of the largest thermal heterogeneous catalytic processes, for its unique selectivity on a solid electrode. However, it is burdened with intrinsic energy losses, operating at Li plating potential. In this work, we survey the periodic table to understand the fundamental features that make Li stand out. Through density functional theory calculations and experimentation on chemistries analogous to lithium (e.g. Na, Mg, Ca), we find that lithium is unique in several ways. It combines a stable nitride that readily decomposes to ammonia, with an ideal solid electrolyte interphase, balancing reagents at the reactive interface. We propose descriptors based on simulated formation and binding energies of key intermediates, and further on hard and soft acids and bases (HSAB principle) to generalize such features. The survey will help the community towards new electrochemical systems for nitrogen fixation.

Single-Atom Catalysts (SAC) have emerged as a promising class of materials for various catalytic applications, including the electrochemical nitrate reduction reaction (eNO3RR) and consequently ammonia production. While the efficiency and selectivity of these materials have been extensively highlighted for the eNO3RR, the in situ evolution to their structure and composition during electrocatalysis is largely unexplored and lacks catalyst design principles. To solve this, we investigated a series of high utilization metal-nitrogen-carbon (MNC) SACs (M = Cr, Fe, Co, Ni, and Cu) for eNO3RR. Except for CuNC, which selectively produced nitrite, all catalysts exhibited Faradaic efficiencies (FE) for ammonia exceeding 50%. NiNC demonstrated the highest performance (FE of 78.0 ± 2.9% at -0.4 V versus reversible hydrogen electrode (RHE) at pH 13 and maximum ammonia production rate of 615.7 ± 176.5 µmol·h-1· cm geo - 2 ${\mathrm{cm}}_{{\mathrm{geo}}}^{ - {\mathrm{2}}}$ , corresponding to an energy efficiency of 15.1 ± 1.4% at -0.6 VRHE), followed by CoNC. In situ Synchrotron X-ray fluorescence (SXRF) mapping at various cathodic potentials (from open circuit potential to 0.0 VRHE and then -0.6 VRHE at 100 mV steps) revealed significant mobility of Ni within the carbon matrix, leading to the formation of metallic clusters from 0.0 VRHE. Similar in situ metal clustering is observed for CoNC. Structure-activity plots are generated from both MNC literature and results obtained here, finding a clear trend between OH binding energy and turnover frequency, with the high activity of NiNC and CoNC in this work explained by their stronger OH binding in the metallic structure compared to their SAC coordination. This work therefore, reveals the structure-activity-stability of MNCs for eNO3RR and provides a simple descriptor for identifying highly active eNO3RR catalysts and their in situ structural evolution.

Establishing reaction paths for heterogeneous catalysis reactions on surfaces by calculating key reaction intermediates from educated guesses has enabled the researcher to derive free energy diagrams and develop mechanistic models for small molecules with limited reaction steps. For reactions with multiple products, reactants, or a large number of reaction steps, proposing and validating a reaction mechanism is extremely challenging, if not impossible. In this work, we propose the use of isomer generators as a tool to generate atomistic reaction networks on catalytic surfaces. We showcase how this tool can be used to carry out exhaustive exploration of reaction paths and generate all products which the reactants can form. From here we count generated intermediates and products arising from multiple CO, NO and combination of reactants, depicting logarithmic scale of complexity in a reaction network of multiple reactants with a large number of reaction steps. We then test a 2CO network on a Cu(111) surface via density functional theory (DFT) simulations to show the difference between educated guesses and automatically generated intermediates. The idea of using molecular isomer generators allows the complete and automatized exploration of complex surface catalytic mechanisms beyond educated guesses.

The selectivity and geometric current density of copper-based electrodes for electrochemical CO2 reduction (CO2RR) have been significantly improved, yet research is striving to improve the intrinsic activity of these materials. The accurate quantification of active sites is vital to benchmark the intrinsic activity of the catalysts for electrochemical CO2 reduction to facilitate activity improvements. Herein, we propose a method to determine the active sites using CO displacement in potassium phosphate buffer at 10 °C. Comparing this method with the electrochemical surface area (ECSA), measured by double-layer capacitance, the most used technique in this field, we demonstrate that CO displacement provides a much more accurate quantification of the number of active sites. By normalizing current density vs the CO displacement active sites, we find electropolished copper foil has the highest intrinsic activity towards CO2RR. We also reveal there is a clear relationship between surface roughness and chained products.

Since its verification in just 2019, there have been numerous high-profile papers reporting improved efficiency of the lithium-mediated electrochemical nitrogen reduction system to make ammonia. However, the literature lacks a cohesive investigation systematically linking bulk electrolyte properties to electrochemical performance and Solid Electrolyte Interphase (SEI) properties. In this study, we vary electrolyte salt concentration and observe a transition from an unstable working electrode potential to working electrode potential stability and peak in Faradaic efficiency of 7.8 ± 0.5 % at 0.6 M LiClO4. The behaviour is linked to the formation of Solvent Separated Ion Pairs in the electrolyte through Raman spectroscopy. Time of Flight Secondary Ion Mass Spectrometry and X-Ray Photoelectron Spectroscopy reveal a more inorganic, and therefore more stable, SEI layer with increasing salt concentration. A drop in Faradaic efficiency is seen at concentrations higher than 0.6 M LiClO4, which is attributed to a combination of a loss in nitrogen solubility and diffusivity as well as increased SEI conductivity as measured by Electrochemical Impedance Spectroscopy.

Macrocycles show high activity for the electrochemical reduction of oxygen in alkaline media. However, even macrocycles with the same metal centers and MN4 active site can vary significantly in activity and selectivity, and to this date, a quantitative insight into the cause of these staggering differences has not been unambiguously reached. These macrocycles form a fundamental platform, similarly to platinum alloys for metal ORR catalyst, to unravel fundamental properties of FeNx catalysts. In this manuscript, we present a systematic study of several macrocycles, with varying active site motif and ligands, using electrochemical techniques, operando spectroscopy, and density functional theory (DFT) simulations. Our study demonstrates the existence of two families of Fe macrocycles for oxygen reduction in alkaline electrolytes: (i) weak *OH binding macrocycles with one peak in the voltammogram and high peroxide selectivity and (ii) macrocycles with close to optimal *OH binding, which exhibit two voltametric peaks and almost no peroxide production. Here, we also propose three mechanisms that would explain our experimental findings. Understanding what differentiates these two families could shed light on how to optimize the activity of pyrolyzed FeNx catalysts.

Electrocatalysis could be a promising approach to produce valuable chemical compounds from carbon and nitrogen reactants. However, several challenges related to activity and selectivity need to be addressed to make these conversion energy and cost-efficient. The NOX reduction is an important reaction for denitrification and here we elucidate how the reaction mechanism controls the product distribution. We investigated the reduction reaction on a series of transition metals (Cu, Ni, Co, Fe, and Mn) to understand the factors governing the associative and dissociative reaction paths. While Cu favors the associative protonation path, the NO-3 and NO-2 reduction on Ni, Co, Fe, and Mn surfaces favor the dissociative reaction pathway. Comparing our DFT computed results with experimental data we found that apart from competing HER the adsorption of *NO2 and its N-O dissociation barrier are two key factors for selective NO-3 reduction towards ammonia and NO-2 . These strategies could be extended to understand energetically robust reactions like N2 and CO2 reduction reactions.

CO2 electrolysis on Cu catalysts at near-ambient conditions yields a range of important C1 to C3 products. Despite recent advances, our mechanistic understanding of the CO2 electrolysis reaction network has remained incomplete, with C4 products, and in particular long sought-after aromatic C6 product molecules, still being elusive. Here, we use a real-time capillary DEMS technique to determine the kinetic onset potentials of a wide set of C1-3 CO2 reduction products. Included in our study are rarely reported products, such as propionaldehyde, propylene, and, first, acetylene, C2H2. We then focus on the formation of acetylene, C2H2, and also investigate its alkyne electro-reduction, the C2H2 reduction reaction (C2H2RR). Acetylene electrodimerizes to the C4 compound 1,3-butadiene in a 2e- reduction reaction. It also revealed a potential-dependent electroless Cu-catalyzed ambient-condition [2 + 2 + 2] cycloaddition reaction to C6 benzene. We discuss mechanisms and the significance of the potential-dependent valorizations of acetylene on Cu. We hypothesize a future process concept to valorize CO2 into sustainable C6 e-aromatics.