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.

Designing a multifunctional electrocatalyst is increasingly in demand. This work deals with successful solution phase synthesis of an ordered compound of Pd and Ni, Pd3Ni, which is assumed to be difficult as almost no adjacent elements in the same group form intermetallic compounds. Pd3Ni is a highly efficient and electrochemically stable material for tetrafunctional activity, in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and ethanol oxidation reaction (EOR), which are involved in both fuel cells and water electrolyzers. Extensive ex situ and in situ characterization has revealed the robustness of this material and the reaction mechanism in different electrochemical reactions. The "local entropy tailoring" reflects the reduced configurational entropy associated with the ordered Pd3Ni lattice relative to the alloy, as evidenced by differential scanning calorimetry, enabling site-specific structural stability. This material has shown promising activity in a proton exchange membrane water electrolyzer and a high temperature fuel cell. The tuned surface of the intermetallic compound has enhanced C-C cleavage in ethanol molecules allowing the sluggish 12e- transfer process, and the compound has shown very high stability for >80000 cycles of alkaline HER. The role of pH and potential has been explored in retaining the ordered phase of the intermetallic compound. Tetrafunctionality and its extensive exploration under different reaction conditions have been exhaustively evaluated in this work.

ABSTRACT Kinetically demanding multi‐step proton‐coupled electron transfer (PCET) and the high energy barrier associated with C─C coupling are the primary reasons for the low selectivity toward multi‐carbon products. Numerous interconnected parameters like catalyst composition, surface structure, doping, morphology, reaction medium, pH, and photocatalytic cell design influence both PCET and C─C coupling. Although these processes are fundamentally independent, they are indirectly affected by the structural and catalytic environmental factors, which often promote one pathway. This interdependence complicates rational catalyst discovery. A critical understanding and careful deconvolution of these parameters are essential for identifying the conditions that synergistically enhance both PCET and C─C coupling for selective product formation. In this review, we present a historical perspective on key catalyst design strategies and mechanistic insights, and highlight the intricate interplay among different catalytic systems, and summarize the latest advancements in CO 2 to C2+ products. Subtle variations in catalyst structure that alter reaction pathways or electron‐transfer dynamics are discussed in detail, as these insights provide powerful guidelines for designing next‐generation C2+ selective photocatalysts. We also emphasize in situ/operando characterization of intermediates, and their energetics relevant to C─C coupling. Finally, we outline current challenges and propose future research directions for advancing the field.

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.

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.

Copper has long been the only element known to produce multicarbon (C 2+ ) products from CO 2 through electrochemical pathways. However, its low kinetic barrier favors ethylene formation over C 2 ⁺ alcohols at the selectivity‐determining step (SDS). Alloying Cu with secondary metals has been explored to shift selectivity toward alcohols, but these approaches often suffer from poor activity and selectivity. In this work, we probe the role of confinement of reaction intermediates in favoring C 2+ alcohol selectivity and overall C 2+ product in oxide‐derived hollow Cu–Zn bimetallic catalysts. From finite element method (FEM) simulation, it was observed that hollow catalyst increases the retention time of the reaction intermediates that favor the C─C coupling. Confinement gives rise to a two‐fold increment in the overall C 2+ product. We observed that the hollow Cu–Zn catalyst gives a Faradaic efficiency (FE) of 50.13% toward C 2+ alcohol and an overall FE of 81% toward C 2+ product at a very high current density of 300 mA cm −2 in 1 M KHCO 3 . DFT calculation shows that Zn affects selectivity determining step (SDS) and favors the formation of alcohol over ethylene. Various in situ techniques, such as X‐ray absorption spectroscopy, infrared spectroscopy, Raman spectroscopy, and differential electrochemical mass spectroscopy, were used to understand the active phase of the catalyst and mechanism in detail.

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.

The photochemical conversion of CO 2 into C2+ products has emerged as an attractive method for synthesizing valuable chemicals and fuels using abundant solar energy. However, the challenge lies in enhancing the efficiency and selectivity of C2+ product formation. In this study, we employed a heteroatom doping strategy to optimize the photocatalytic parameters and achieve excellent efficiency and selectivity in the photocatalytic CO 2 reduction to C2+ product formation. Our experimental analysis revealed that the local electronic structure of the catalyst, modified by In-doping, enables enhanced efficiency. Additionally, the incorporation of Cu facilitates the coupling of C1 intermediates, resulting in excellent selectivity towards C2+ products. The CO 2 reduction performance is further enhanced through exfoliation, which increases the exposure of active sites and extends the charge carrier lifetime by reducing the charge diffusion length. We report that the rate of formation of C 2 H 4 reached 54.3 µmol·h −1 ·g −1 with an outstanding selectivity of 91% over the exfoliated CuIn-doped AgBiP 2 S 6 catalyst. By elucidating the role of heteroatom doping and exfoliation in enhancing both the efficiency and selectivity of C2+ product formation, our study contributes to advancing the development of sustainable and efficient photocatalytic CO 2 conversion technologies.

Nitrogen-doped perovskites (LaMnO3) were designed as bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Nitridation led to O-substitution in LaMnO3, creating distortion in the LaMnO3 structure and generating oxygen vacancies. N-doping facilitated an increase of Mn3+ content, enhancing ORR and OER activities. LaMnO3 with 4 h of nitridation exhibits 3.35 and 1.75 times higher specific and mass activities in comparison to pristine LaMnO3 (highest reported among perovskite oxides). The enhancement in catalytic activity is attributed to the increase of Mn3+ content and distorted Mn-O, leading to compressive strain. The substitution of N at the crystal lattice of perovskite stabilizes the intermediates through a combination of strain and charge modulation of the active Mn center, which causes the enhancement in ORR and OER performance. The bifunctional character of the catalyst was further evaluated for practical zinc-air battery applications in which nitrogen-doped LaMnO3 undergoes steady operation up to 500 cycles in harsh industrial conditions of 6 M KOH.

Mitigating global CO2 concentrations from anthropogenic sources through electrochemical conversion to value-added chemicals is the need of the hour. In this work, the fundamental concept of "Lattice Charge" has been strategically manipulated in materials to selectively produce multi-carbon products from greenhouse CO2 gas. To achieve this, a series of catalysts within a well-known ABX(2) family (A = Ag, Cu; B = In, Ga, Fe; X = S, Se) have been explored, which exhibit significant activity toward the electrochemical CO2 reduction reaction (eCO(2)RR) and results in the formation of higher carbon chemicals including C-3 products, acetone, and energy-dense isopropanol (FE = 24.5 +/- 2.5%). The Hirshfeld charge analysis technique highlighted the structure-activity correlation and the importance of the optimized lattice charge distribution as a crucial tool to manipulate the eCO(2)RR product in electrocatalyst designs, and the real-time in situ ATR-FTIR technique probes the crucial intermediate species adsorbed during the CO2 reduction process.

Electrochemical CO2 reduction reaction (eCO(2)RR) has been explored on tungsten carbide (WC) nanoparticles embedded on N-doped graphitic carbon (NGC), demonstrating excellent activity toward the formation of acetic acid at an extremely lower potential. The activity has been further enhanced by loading ultralow copper sites into the catalyst system, exhibiting 80.02% Faradaic efficiency (FE) toward acetic acid at an applied potential of -0.3 V (vs RHE). Potential-dependent in situ infrared (IR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, ex situ extended X-ray absorption fine structure (EXAFS) studies, and computational analysis confirm that synergy between uniformly dispersed Cu atoms and WC lattice plays a crucial role in the formation of acetic acid with high FE at a lower potential. It has been observed that the W atom of WC strongly chemisorbs CO2 with a significant change in the C-O bond length and the O-C-O bond angle, in contrast to weaker adsorption on Cu-based catalyst surfaces. The presence of a Cu site enhances the adsorption of CO2, thereby increasing the possibility of C-C coupling kinetically. Most importantly, hydrogen evolution predominates on the catalyst's surface at higher applied potentials (-0.5 to -1.1 V vs RHE), elucidating the mechanism underlying enhanced charge transfer between copper and WC, a phenomenon ascertained through in situ IR spectroscopy and ex situ XPS analysis

A common challenge in electrochemical processes is developing high performance, stable catalysts for specific chemical reactions. In this work, a Pd-Sn intermetallic compound with   Pd site deficiency (Pd1.9-xSn) (x = 0.06) and trace amount of SnOx was synthesised by controlled process. Under the electrochemical conditions, the deficient Pd site is filled by metallic Sn, which generates a highly active and stable (Pd1.84Sn0.06)Sn catalyst for ethanol oxidation reaction (EOR). The crystal structure and atomic arrangements for synthesized and in situ generated compound are comprehensively characterized by various spectroscopic techniques. The in situ generated catalyst exhibits excellent performance toward EOR (anodic reaction in fuel cell), which outperforms the state-of-the-art Pd/C catalyst by three times in terms of activity. Furthermore, it is observed that the catalyst preferentially cleaves the CC bond in ethanol, which is a crucial process that enhances the efficiency of the fuel cells. The catalyst retains its superlative activity even after 1500 cycles of continuous operation. The mechanism for EOR and CC bond cleavage is evidenced by operando Infra Red spectroscopy and Differential Electrochemical Mass Spectroscopy (DEMS), and the driving force toward excellent performance has been proposed via theoretical calculations.

The electrochemical reductive valorization of CO2, referred to as the CO2RR, is an emerging approach for the conversion of CO2-containing feeds into valuable carbonaceous fuels and chemicals, with potential contributions to carbon capture and use (CCU) for reducing greenhouse gas emissions. Copper surfaces and graphene-embedded, N-coordinated single metal atom (MNC) catalysts exhibit distinctive reactivity, attracting attention as efficient electrocatalysts for CO2RR. This review offers a comparative analysis of CO2RR on copper surfaces and MNC catalysts, highlighting their unique characteristics in terms of CO2 activation, C1/C2(+) product formation, and the competing hydrogen evolution pathway. The assessment underscores the significance of understanding structure-activity relationships to optimize catalyst design for efficient and selective CO2RR. Examining detailed reaction mechanisms and structure-selectivity patterns, the analysis explores recent insights into changes in the chemical catalyst states, atomic motif rearrangements, and fractal agglomeration, providing essential kinetic information from advanced in/ex situ microscopy/spectroscopy techniques. At the end, this review addresses future challenges and solutions related to today's disconnect between our current molecular understanding of structure-activity-selectivity relations in CO2RR and the relevant factors controlling the performance of CO2 electrolyzers over longer times, with larger electrode sizes, and at higher current densities.

It is widely established that the electroreduction of carbon dioxide on a copper surface yields a spectrum of alcohols and hydrocarbons. But the selectivity of Cu toward a certain product is extremely poor as it forms a variety of reduced products concurrently. Controlling selectivity and overall performance depends on the modification of the Cu site and local environment. This study depicts how the product selectivity can be switched from C1 to C2 and multicarbon products by systematic incorporation of secondary metal (Pd) into the Cu lattice. Upon releasing the structural ordering from intermetallic to alloy and then to bimetallic, a systematic enhancement on the formation of C2 products from CO2 has been observed. Real-time in situ X-ray absorption spectroscopy (XAS) study showed the potential dependent evolution of Pd & horbar;Cu and Cu & horbar;Cu bonds in different Pd-Cu-based catalysts. The detailed analysis of in situ IR and Raman also determined the adsorbed intermediate species and helped to identify the mechanism. Computational studies show the feasibility of multicarbon product formation on bimetallic catalysts compared to alloy and intermetallic catalysts. The current density and the activity of the CO2 electroreduction have been enhanced by the utilization of the flow cell in the gas diffusion electrode configuration.

In this work, atomic cobalt (Co) incorporation into the Pd2Ge intermetallic lattice facilitates operando generation of a thin layer of CoO over Co-substituted Pd2Ge, with Co in the CoO surface layer functioning as single metal sites. Hence the catalyst has been titled Co1-CoO-Pd2Ge. High-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy confirm the existence of CoO, with some of the Co bonded to Ge by substitution of Pd sites in the Pd2Ge lattice. The role of the CoO layer in the oxygen evolution reaction (OER) has been verified by its selective removal using argon sputtering and conducting the OER on the etched catalyst. In situ X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy demonstrate that CoO gets transformed to CoOOH (Co3+) in operando condition with faster charge transfer through Pd atoms in the core Pd2Ge lattice. In situ Raman spectroscopy depicts the emergence of a CoOOH phase on applying potential and shows that the phase is stable with increasing potential and time without getting converted to CoO2. Density functional theory calculations indicate that the Pd2Ge lattice induces distortion in the CoO phase and generates unpaired spins in a nonmagnetic CoOOH system resulting in an increase in the OER activity and durability. The existence of spin density even after electrocatalysis is verified from electron paramagnetic resonance spectroscopy. We have thus successfully synthesized intermetallic supported CoO during synthesis and rigorously verified the role played by an intermetallic Pd2Ge core in enhancing charge transfer, generating spin density, improving electrochemical durability, and imparting mechanical stability to a thin CoOOH overlayer. Differential electrochemical mass spectrometry has been explored to visualize the instantaneous generation of oxygen gas during the onset of the reaction.

The conversion of CO2 to a sole carbonaceous product using photocatalysis is a sustainable solution for alleviating the increasing levels of CO2 emissions and reducing our dependence on nonrenewable resources such as fossil fuels. However, developing a photoactive, metal-free catalyst that is highly selective and efficient in the CO2 reduction reaction (CO2RR) without the need for sacrificial agents, cocatalysts, and photosensitizers is challenging. Furthermore, due to the poor solubility of CO2 in water and the kinetically and thermodynamically favored hydrogen evolution reaction (HER), designing a highly selective photocatalyst is challenging. Here, we propose a molecular engineering approach to design a photoactive polymer with high CO2 permeability and low water diffusivity, promoting the mass transfer of CO2 while suppressing HER. We have incorporated a contorted triptycene scaffold with "internal molecular free volume (IMFV)" to enhance gas permeability to the active site by creating molecular channels through the inefficient packing of polymer chains. Additionally, we introduced a pyrene moiety to promote visible-light harvesting capability and charge separation. By leveraging these qualities, the polymer exhibited a high CO generation rate of 77.8 μmol g-1 h-1, with a high selectivity of ∼98% and good recyclability. The importance of IMFV was highlighted by replacing the contorted triptycene unit with a planar scaffold, which led to a selectivity reversal favoring HER over CO2RR in water. In situ electron paramagnetic resonance (EPR), time-resolved photoluminescence spectroscopy (TRPL), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques, further supported by theoretical calculations, were employed to enlighten the mechanistic insight for metal-free CO2 reduction to exclusively CO in water.

We present surface reconstruction-induced C−C coupling whereby CO 2 is converted into ethylene. The wurtzite phase of CuGaS 2. undergoes in situ surface reconstruction, leading to the formation of a thin CuO layer over the pristine catalyst, which facilitates selective conversion of CO 2 to ethylene (C 2 H 4 ). Upon illumination, the catalyst efficiently converts CO 2 to C 2 H 4 with 75.1 % selectivity (92.7 % selectivity in terms of R electron ) and a 20.6 μmol g −1  h −1 evolution rate. Subsequent spectroscopic and microscopic studies supported by theoretical analysis revealed operando-generated Cu 2+ , with the assistance of existing Cu + , functioning as an anchor for the generated *CO and thereby facilitating C−C coupling. This study demonstrates strain-induced in situ surface reconstruction leading to heterojunction formation, which finetunes the oxidation state of Cu and modulates the CO 2 reduction reaction pathway to selective formation of ethylene.

Conversion of CO2 to higher alcohols (HAs) and higher hydrocarbons (HCs) has a greater advantage compared to C1 products because of their high energy density and wide range of applications in daily life. Despite the immense potential of these chemicals, not much of scientific research has been focused on the conversion of CO2 to HAs. In the present work, we have introduced the concept of strain in designing the material to enhance the CO2 to HA performance. We introduced strain in a traditional iron-based catalyst, Fe2O3, by the introduction of indium (In), which facilitates the selective conversion of CO2 to HA. An optimum strain favored a 36.7% CO2 conversion with a 42% HA selectivity, and a record yield of 15.42%. The strain has been tuned further with the introduction of K as a promoter. The introduced strain upon In substitution and K promotion favored the conversion of CO2, which is mapped by powder X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Further, the change in the mechanism upon In incorporation and K promotion has been probed by in situ diffuse reflectance infrared fourier transform spectroscopy, and it is found that the OCHx intermediate, which produces HAs, is more prominent upon In substitution, which favored the enhancement of HA production compared to that of pristine Fe2O3.

The well-known limitation of alkaline fuel cells is the slack kinetics of the cathodic half-cell reaction, the oxygen reduction reaction (ORR). Platinum, being the most active ORR catalyst, is still facing challenges due to its corrosive nature and sluggish kinetics. Many novel approaches for substituting Pt have been reported, which suffer from stability issues even after mighty modifications. Designing an extremely stable, but unexplored ordered intermetallic structure, Pd2Ge, and tuning the electronic environment of the active sites by site-selective Pt substitution to overcome the hurdle of alkaline ORR is the main motive of this paper. The substitution of platinum atoms at a specific Pd position leads to Pt0.2Pd1.8Ge demonstrating a half-wave potential (E1/2) of 0.95 V vs RHE, which outperforms the state-of-the-art catalyst 20% Pt/C. The mass activity (MA) of Pt0.2Pd1.8Ge is 320 mA/mgPt, which is almost 3.2 times better than that of Pt/C. E1/2 and MA remained unaltered even after 50,000 accelerated degradation test (ADT) cycles, which makes it a promising stable catalyst with its activity better than that of the state-of-the-art Pt/C. The undesired 2e- transfer ORR forming hydrogen peroxide (H2O2) is diminished in Pt0.2Pd1.8Ge as visible from the rotating ring-disk electrode (RRDE) experiment, spectroscopically visualized by in situ Fourier transform infrared (FTIR) spectroscopy and supported by computational studies. The effect of Pt substitution on Pd has been properly manifested by X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS). The swinging of the oxidation state of atomic sites of Pt0.2Pd1.8Ge during the reaction is probed by in situ XAS, which efficiently enhances 4e- transfer, producing an extremely low percentage of H2O2.