Understanding C─C coupling pathways is essential for achieving selective CO 2 conversion into multi‐carbon products. However, controlling intermediates dimerization remains highly challenging due to both the complexity of the catalytic systems and the limited mechanistic knowledge into the C─C coupling process. In this work, a model dual‐site catalyst with precisely configured Fe‐O‐Cu sites is designed by covalently grafting iron‐phthalocyanine (FePc) onto copper nanowires via oxygen bridges (FeN 4 ‐O‐Cu NW), which enables probing of atomic‐level mechanistic insights into the C─C coupling pathways during electrochemical CO 2 reduction reaction (CO 2 RR). Remarkably, the FeN 4 ‐O‐Cu NW exhibits a 23.6‐fold enhancement in the ethanol‐to‐ethylene Faradaic efficiency ratio as compared to O‐Cu NW, achieving > 80% C 2+ Faradaic efficiency at an industrially relevant current density of 1 A cm −2 . 13 CO 2 / 12 CO co‐feed experiments together with a collection of operando /in‐situ characterizations reveal that the enhanced ethanol selectivity over FeN 4 ‐O‐Cu NW arises from asymmetric C─C coupling between *CO and *CHO intermediates, where *CO is generated at the low‐spin single‐Fe‐atom site, while *CHO is produced at the oxygen‐bridged Cu site. Density functional theory (DFT) calculations further unveil that the oxygen‐bridged Fe‐O‐Cu site can not only stabilize the in situ generated low‐spin Fe(II) active site for enhancing CO 2 activation and lowering *CO desorption energy but also construct an oxygen‐bridged Cu active site to stabilize the *OCHO intermediate, significantly lowering the *OCHO‐to‐*CHO conversion energy barrier, orchestrating an efficient asymmetric *CO─*CHO coupling path and boosting the CO 2 ‐to‐ethanol conversion.

High-valent iron oxo species (Fe(IV)) are attractive for wastewater treatment because of their high selectivity toward organic pollutants in complex water matrices, but their intrinsic redox properties drive rapid quenching by peroxide precursors, causing excessive chemical consumption. This work addresses this challenge by anchoring Fe(IV) on an iron-phthalocyanine-based conjugated organic framework (FePPC) featuring multi-layered reticular structures and strong π-Fe3d-O2p orbital overlapping. The two-dimensional planar structures provided easily accessible active sites and the extended in-plane conjugation fine-tunes the redox reactivity of surface-confined Fe(IV) species, suppressing unproductive decay while preserving selectivity toward diverse pollutants, yielding a 3.2-fold enhancement in Fe(IV) utilization efficiency. Combined experimental and computational results show that the enhanced orbital overlapping delocalizes electrons at the Fe(IV)═O bond and reduces occupancy of its anti-bonding π* orbital, thereby strengthening the bond against nucleophilic attack by peroxymonosulfate, suppressing O2 evolution, and improving both pollutant selectivity and peroxide stoichiometric efficiency. When integrated into a scale-up membrane reactor, FePPC achieved over 95% micropollutant removal during 72 h of continuous operation. This work fills an important knowledge gap in understanding Fe(IV) redox properties and selectivity, addressing technical bottlenecks in Fe(IV)-based AOP systems toward low-chemical consumption and high-efficiency wastewater treatment.

Geminal-site catalysts (GSCs) are prospective candidates for fulfilling the goal of aqueous electrochemical reductive cross-coupling reactions (ERCR) at near-stoichiometric yields. Nevertheless, a problem lies in the lack of a synthetic route for GSCs with few single sites. Here we report a defect-accompanying strategy for synthesizing GSCs containing metal-defect catalytic pairs (M-D GSCs), meaning that Fe-D GSCs can realize the electrochemical synthesis of cyclohexanone oximes (CHOs) from high concentrations (0.5 M) of nitrites (NO2 -) and cyclohexanone (CYC) at near-stoichiometric yields (the Faradic efficiency or yieldC/N: 91.3%). Multiple in-/ex-situ characterizations demonstrated that metal-citrate complexes were converted to metal-defect catalytic pairs via the liberation of gaseous carbon/nitrogen species during pyrolysis. Furthermore, we developed an innovative cathodic oxime-alkali process, where high concentration NaNO2 and CYC can be electrochemically converted to high-purity products including NaOH and CHO. This work showcases the enormous potential of M-D GSCs in achieving near-stoichiometric conversion for ERCR reactions.

ABSTRACT A dual‐layer structured catalyst (S‐NiFeO x H y /NiFe) comprising an inner nickel sulfide layer and an outer iron oxide layer was constructed on a nickel‐iron foam through a combined approach of electrochemical treatment and selective hydrothermal sulfidation. This catalyst demonstrates exceptional OER activity and remarkable stability under alkaline conditions, achieving overpotentials as low as 216.6 and 287.0 mV at current densities of 100 and 300 mA cm −2 , respectively, while maintaining stable operation for over 9000 and 7300 h. Using various in situ characterization techniques, the sulfur loss‐triggered dynamic reconstruction process is systematically elucidated, whereby nickel sulfide transforms into highly active NiOOH, while FeOOH undergoes nanoscale refinement and valence elevation, collectively forming an efficient catalytic interface. The reaction proceeds via a synergistic combination of the lattice oxygen mechanism (LOM) and the adsorbate evolution mechanism (AEM), with NiOOH primarily facilitating LOM for high efficiency and FeOOH favoring AEM for excellent stability. This dual‐mechanism coupling significantly enhances both reaction efficiency and durability. The surface iron oxide layer effectively suppresses sulfur dissolution, maintaining a slow and controllable reconstruction cycle that ensures long‐term catalyst stability. This work provides new insights into the design of high‐performance electrocatalysts through dynamic reconstruction and mechanistic synergy strategies.

Sustainable carbon management through innovative strategies is essential to address the dual crises of climate change and resource scarcity. Electrochemical CO2 reduction reaction (CO2RR) and biomass electrooxidation (BEO) represent two promising pathways for converting CO2 and renewable biomass into valuable chemicals. While previous reviews have broadly covered replacing the energy-intensive anodic oxygen evolution reaction (OER) for CO2RR, they often lack an integrated analysis of the complementary challenges and design principles for CO2RR & BEO coupling system. This review fills this gap by critically analyzing their core key limitations, notably the high energy cost of OER in CO2RR and the low economic return from the hydrogen evolution reaction (HER) in BEO; meanwhile, the design principles, e.g., potential matching, pH and product compatibility, for the couple system are proposed. Moreover, coupled systems that effectively exploit the complementary nature of CO2RR & BEO are systematically presented, including CO2RR paired with the oxidation of biomass-derived molecules and other substrates (e.g., glucose, alcohols, aldehydes, methane, chlorides, sulfides) and BEO coupled with other cathodic reductions (e.g., furfural, 4-nitrophenol). Meanwhile, their compatibility in term of potential, pH and product were analyzed and compared. Finally, future research directions are outlined, with emphasis on innovative catalysts design, system-level optimization, and scalable implementation. This work provides a focused perspective on advancing sustainable resource utilization through electrochemical coupling.

Selective oxidation-driven pollutant polymerization enables simultaneous contaminant removal and carbon recovery, yet current catalysts suffer from competitive adsorption between pollutants and oxidants, disrupting redox balance and causing premature termination. Herein, we present a microenvironment-decoupled strategy by anchoring atomically dispersed Sn on amino-functionalized carbon nanotubes (CNT-NH2). Amino preferentially stabilizes Sn as Sn(II)-N4, which selectively activates peroxydisulfate (PDS) by forming a bidentate Sn-PDS complex and sustains an electron-transfer-dominated pathway. Meanwhile, the carbon surface enriches phenolic substrates and sustains their para-C-O polymerization transfer. In situ spectroscopy and density functional theory identify Sn 5p-O 2p interactions as the origin of this unique selectivity. As a result, the SnPc/CNT-NH2/PDS system maintains over 95% phenol removal after five cycles (versus one cycle for CNT) and achieves ~82% total organic carbon removal (versus ~46% for CNT). A decoupled reactor further demonstrates the practical feasibility of this mechanism for continuous water purification. This work provides a microenvironment-decoupled paradigm for precise oxidation regulation toward sustainable pollutant polymerization transfer in water purification.

Iron-nitrogen-carbon (FeNC) catalysts are considered among the most promising alternative to Pt catalysts in acidic oxygen reduction reaction (ORR), yet the geometric and electronic structures of the true active site under reaction conditions have not been clearly elucidated. Herein, we synthesized a representative FeNC catalyst by pyrolyzing Fe3+ absorbed on ZIF-8-derived N-doped carbon at a mild temperature under the H-2/Ar atmosphere, where a formation mechanism of FeN4 sites through a Zn-mediated Fe nanoparticle atomization process was proposed. The resulting FeNC-750 catalyst shows high acidic ORR activity with a half-wave potential of 0.838 V and a peak power density of 1 W cm(-2) in proton-exchange membrane fuel cell (PEMFC). By using operando(57)Fe M & ouml;ssbauer spectroscopy on FeNC-750, it was revealed that the pyrrolic N-coordinated high-spin Fe2+N4 sites, which are in situ generated from high-spin Fe3+N4 during ORR, are identified as catalytic active states. Density functional theory calculations further verified that, compared to the pyridinic N-coordinated low-spin Fe2+N4, the pyrrolic N-coordinated high-spin Fe2+ exhibits optimized adsorption energy for reaction intermediates, thereby lowering the energy barrier of the rate-determining step (RDS) and facilitating OH* desorption. This work provides both experimental and theoretical evidence of the true active site in the FeNC during acidic ORR, offering significant insights for the rational design of high-performance materials for acidic fuel cells.

Hydrogen peroxide (H2O2) is an essential chemical whose conventional production is environmentally unsustainable, driving the pursuit of electrochemical synthesis via the two-electron oxygen reduction reaction (2e- ORR). However, the intractable trade-off between activity and stability hampers its industrialization, spin-control engineering offers a compelling strategy that maintains structural integrity while enabling reversible electronic tunability. Herein, we demonstrate a CoFe Prussian blue analogue (CoFe PBA) catalyst with precisely regulated atomic coordination (Co & horbar;N & horbar;C & horbar;Fe) and spin states, enabling simultaneous high activity, selectivity, and stability in the 2e- ORR for H2O2 production. This synergistic configuration pairs high-spin Co sites, which facilitate strong O2 adsorption, with low-spin Fe sites that ensure structural robustness. The concerted effect of these sites effectively suppresses O & horbar;O bond cleavage, thereby guaranteeing high selectivity for H2O2 generation. Consequently, CoFe PBA exhibits exceptional performance, achieving not only a high H2O2 production rate of 6.74 mol gcat -1 h-1 with near-100% initial selectivity but also outstanding operational stability, retaining 92.93% of its selectivity even after 3000 cycles in a concentrated alkaline electrolyte. Our work highlights spin-state engineering as a viable strategy to overcome the longstanding activity, selectivity-stability trade-off in electro-synthesis H2O2.

Poly(vinyl chloride) (PVC) poses a persistent environmental challenge due to its high chlorine content and additive-mediated recalcitrance. Herein, we report an N,O-dual-coordinated iron single-atom catalyst (Fe-N2O2-hCN) integrated with palladium nanoparticles (Pd NPs) for efficient hydrothermal Fenton-like upcycling of PVC into fuel-range hydrocarbons. The asymmetric Fe-N2O2 configuration modulates the electronic structure of Fe centers, promoting H2O2 activation and hydroxyl radical generation for efficient C-Cl and C-C bond cleavage under mild conditions, outperforming the conventional Fe-N4 catalyst. The bifunctional Pd NPs/Fe-N2O2-hCN system achieves high PVC degradation efficiency (97.38%) and near-complete dechlorination, while selectively hydrogenating depolymerized intermediates into fuel-range alkanes (C3-C20) with a high selectivity (86.01%). Mechanistic studies reveal enhanced electron transfer and a lowered energy barrier for H2O2 dissociation, with Pd NPs generating reactive hydrogen species for olefin saturation. Life cycle assessment (LCA) demonstrates a 77% reduction in carbon emissions and significantly lower eco-costs than incineration. This work provides a coordination-engineered platform for converting hazardous plastic waste into valuable fuels, advancing a circular plastic economy.

Sustainable synthesis of analytical-grade propanal from CO2 and H2O via an electro-thermal cascade process is highly attractive but remains challenging due to the limited selectivity of CO2 electroreduction to gaseous products (CO/C2H4) and the sluggish kinetics of the subsequent thermal catalytic step at ambient pressure. In this work, we demonstrate a new pathway for the direct synthesis of purification-free analytical-grade propanal via electroreduction-hydroformylation cascade conversion of CO2 and H2O over rationally designed single-atom catalysts (SACs). The Sn1Cu single-atom alloy (SAA) catalyst exhibits an exceptional potential-dependent CO2 electroreduction selectivity toward C2H4 and CO, with the C2H4 to CO ratio increasing by 2 orders of magnitude in the potential range from -0.6 to -2.3 V (vs RHE). Results from in situ/operando characterizations and density functional theory (DFT) calculations reveal that the enhanced ethylene selectivity over Sn1Cu SAA arises from the high *CO coverage generated over a single-Sn-atom-modified Cu site, which promotes the symmetric *CO-*CO coupling, thereby significantly enhancing the electrochemical CO2 reduction to ethylene. The resulting C2H4/CO/H2 mixture is directly converted in a fixed-bed hydroformylation reactor over a triphenylphosphine-modified Rh SAC (PPh3-Rh1/ZnO), achieving an optimized ethylene-to-propanal selectivity of up to 98%. Analytical-grade propanal (∼99%) is obtained without further purification, and stable production was maintained for 200 h with a maximum C3H6O rate of 3.8 mg h-1 cm-2 under ambient pressure. This work establishes a general framework for integrating electrochemical and thermal catalysis to convert CO2 and H2O into value-added aldehydes, offering a sustainable route for synthesizing value-added chemicals from basic feedstocks.

The hydrogenation of CO2 to light olefins is a key route for converting waste carbon into value-added chemicals, and FeCx catalysts exhibit high activity and promising application potential. However, FeCx or Fe0 active sites can be oxidized by H2O generated during the reaction, severely compromising the activity and stability of Fe-based catalysts. Herein, FeCx active species confined within F-doped mesoporous carbon were prepared using a F-functionalized carbon source, constructing a H2O-resistant interface to protect FeCx from oxidation. Under the reaction conditions of 320 °C, 3.0 MPa, H2/CO2 = 3, and GHSV = 6000 mL/gcat/h, the 0.8Fe-0.1K@NMC-0.2F catalyst exhibited a CO2 conversion of 47.24% and a light-olefin selectivity of 52.43%. A light-olefin space-time yield of 36.5 mmol/gcat/h was achieved over 100 h at a high GHSV of 24,000 mL/gcat/h, surpassing the performance of most reported catalysts. The structure-performance relationship and stability enhancement mechanism were investigated using various characterization techniques, revealing that F incorporation enhances the graphitization degree and H2O resistance of the carbon layer, regulates the electron distribution, and promotes the formation of unsaturatedly coordinated Fe5C2 active sites. The F-doped graphene interface modulated the electronic structure of FeCx active sites to enhance CO2 adsorption-dissociation while weakening H2 activation, increasing the surface C/H ratio, and promoting the C-C coupling reaction. Furthermore, the F-functionalized graphene layer suppressed the overcarbonization and H2O-induced oxidation of Fe0 species, boosting the catalytic stability. This work provides a new strategy for the design of high-performance and long-lifetime FeCx catalysts for the cost-effective conversion of CO2 to high-value chemicals and new insights into the stability enhancement mechanism of Fe active sites against H2O generated during the hydrogenation reaction.

Spin state regulation has emerged as a promising strategy to enhance the catalytic performance of transition-metal catalysts in peroxymonosulfate (PMS) activation. Herein, boron doping and facet engineering were synergistically applied to regulate the spin state of hematite, yielding B-doped hematite nanorods (B-HNRs) and nanocubes (B-HNCs) with highly efficient PMS activation and abundant 1O2 production. X-ray absorption near-edge structure (XANES) and 57Fe Mössbauer spectra analysis revealed that the boron incorporation resulted in the formation of high spin (HS) Fe(II) species with smaller crystal field splitting energy compared to Fe(III). Density functional theory (DFT) calculations revealed that boron doping enhanced the overlap between Fe 3d orbitals and O 2p orbitals of PMS molecules, thereby facilitating electron transfer between PMS and Fe centers. Compared with B-HNCs, B-HNRs possessing more HS Fe(II) exhibited stronger PMS adsorption, greater OO bond activation, and consequently achieved higher 1O2 selectivity (91.6%) and superior catalytic performance. The generated 1O2 displayed strong resistance to common aqueous interferences and enabled selective pollutant oxidation. Furthermore, the successful continuous-flow reactor operation demonstrated its practical application potential. This work not only offers an innovative approach for the rational modification of transition-metal catalysts but also deepens the mechanistic understanding of PMS activation at the atomic level.

MnO2 is a widely studied non-noble metal electrocatalyst for the oxygen evolution reaction (OER) and has demonstrated phase-dependent performance. Among the various MnO2 polymorphs, gamma-MnO2 has abundant defects and vacancies due to its disordered crystal structure of both beta-MnO2 and R-MnO2 intergrowth, thus being a potential high-performance OER catalyst. However, gamma-MnO2 has been studied much less than other crystal phases of MnO2, and gamma-MnO2-based heterostructures are rarely reported. In this study, it is discovered that gamma-phase plays a unique role in RuOx/MnO2 heterostructured nanorods. Among the pristine alpha-, beta-, and gamma-MnO2 polymorphs, alpha-phase shows the best OER activity; however, after loading RuOx nanoclusters, RuOx/gamma-MnO2 shows the largest enhancement and hence the best OER activity with an overpotential of 255 mV at 10 mA cm(-2) and excellent stability (> 300 h), which is much superior to the commercial RuO2 catalyst. Furthermore, when tested in an anion exchange membrane water electrolyzer (AEMWE), it maintains excellent durability at 200 mA cm(-2) over 380 h. Mechanistic study shows that RuOx/gamma-MnO2 exhibits the strongest electron transfer between Ru and Mn, which significantly weakens the Mn-O bond strength and reduces the interaction between intermediates and the MnO2 surface, ultimately resulting in the lowest energy barrier for the reaction.

Anodic oxygen evolution reaction (OER) that involves a spin-dependent singlet-to-triplet oxygen changeover largely restrains the water electrolysis efficiency for hydrogen production. However, the modulation of spin state is still challengeable for most OER catalysts, and there remains a debate on deciphering the active spin state in OER. Here, we pioneered an asymmetric Fe-incorporated NiPS 3 tactic system to retune the metal localized spin for efficient OER electrocatalysis. It is unraveled that the synergistic effect of medium-spin Fe III site and P/S coordination can effectively boost OER activity and Cl resistance selectivity in alkaline/sea water. Resultantly, the Fe/NiPS 3 -based asymmetric electrodes exhibit low cell voltages of 1.50 volts/1.52 volts in alkaline/sea water at 10 milliamperes per square centimeter, together with a sustainable retention for 1000 hours. It also delivers the durable performance in anion exchange membrane water electrolyzers with a low operation voltage at 45°C. This research navigates the atomic localized spin state as the criterion in rationalizing efficient nonprecious alkaline/sea water oxidation electrocatalysts.

Hydroxylamine (NH2OH) is an important feedstock for oxime production. Coreduction of NOx and aldehydes or ketones enables sustainable one-step oximation by utilizing in situ *NH2OH intermediates but suffers from side reactions and reduced current density due to the presence of multiple reactants in one reactor. Here we decouple oximation into two steps, the electrochemical synthesis of free NH2OH via nitrite (NO2−) electroreduction and the aldehyde or ketone oximation chemical step, circumventing the negative effects (such as site blocking, aldehyde or ketone electroreduction, or crossover) encountered in one-step oximation. By using a Ketjen-black-supported iron phthalocyanine as the catalyst, we achieve an exceptionally high partial current density of free NH2OH (jNH2OH) of 262.9 mA cm−2 (corresponding to productivity of 2.452 mmol cm−2 h−1) in neutral conditions at an industrially relevant current density of 500 mA cm−2. By coupling NH2OH electrosynthesis with subsequent oximation in two steps, nearly stoichiometric oximes are produced with high efficiency and broad applicability. This work paves the way toward a sustainable oxime industry. A sustainable two-step strategy for oxime synthesis in a neutral KHCO3 medium is reported. Free-state NH2OH is initially synthesized via nitrite electroreduction over a Ketjen-black-supported iron phthalocyanine catalyst, followed by a chemical aldehyde or ketone oximation using the electrochemically synthesized NH2OH.

The electrochemical oxidation of propylene presents a promising strategy for propylene oxide (PO) synthesis, but is severely hindered by the complex reaction pathways and the low PO selectivity. In this work, a series of Ag-decorated FeOOH catalysts is designed to elucidate the reaction mechanism of the electrochemical propylene oxidation reaction for PO electrosynthesis. An optimal Faradaic efficiency of PO of 32.0% is achieved over the single-Ag-atom decorated FeOOH catalyst (Ag1-FeOOH) at 2.4 V versus reversible hydrogen electrode. The in-situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy and in-situ 57Fe Mössbauer spectroscopy measurements combined with density functional theory calculations reveal the dual-site synergistic catalytic mechanism for electrochemical propylene epoxidation over Ag1-FeOOH, where single-Ag-atom sites catalyze water oxidation to generate reactive oxygen species, while the adjacent Fe sites serve as adsorption sites for propylene activation. This study provides clear insights into the dual-site synergistic electrocatalytic mechanism of propylene epoxidation and sheds light on the rational design of single-atom catalysts for electrochemical organic synthesis.

In the field of wastewater treatment, the regulation of free radical and non-radical routes has been one of the major challenges. This study investigates the regulation of radical and non-radical oxidation pathways in the peroxymonosulfate (PMS) oxidation system by controlling the calcination temperature of carbon materials and constructing bimetallic single-atom catalysts (NC-FeMn(TA)). Density functional theory calculations and experimental tests indicate that increasing the pyridinic nitrogen content and incorporating single metal atoms in nitrogen-doped carbon materials result in a predominantly non-radical oxidation process. In contrast, enhancing the content of graphitic and pyrrolic nitrogen species and introducing bimetallic catalytic centers promote a radical oxidation pathway. The NC-FeMn(TA)/PMS system demonstrates high oxidation performance over a broad pH range, exhibiting significant interference resistance and stability, with 100% degradation of target pollutants after 22 cycles and complete removal of emerging pollutants (including pharmaceuticals and personal care products, endocrine disrupting chemicals, dyes and chemical materials) within 5 min. This system's remarkable performance suggests broad application potential in water pollution control field.

The dynamic catalyst's restructuring creates a new catalytic surface that is essential for boosting the efficiency of electrochemical carbon dioxide reduction reaction (CO 2 RR). In this work, we synthesize Ag‐decorated SnS 2 hollow microboxes using a coprecipitation method followed by a hydrothermal treatment. Based on a collection of in‐situ/ex‐situ characterizations including in‐situ Raman spectroscopy, rapid freeze‐quench (RFQ) 119 Sn Mössbauer spectroscopy, X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS), we discover that the Ag‐decorated SnS 2 (Ag@SnS 2 ) hollow microboxes undergo dynamic reduction and reconstruction during the electrochemical CO 2 RR, leading to the in‐situ formation of S‐doped Ag–Sn alloy (S‐Ag 3 Sn/Sn) hollow microboxes. This transformation results in a remarkable formate selectivity of 92.4% with a formate partial current density of 97.3 mA·cm −2 at −0.8 V versus RHE in an H‐cell. In‐situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) measurements and density functional theory (DFT) calculations indicate that both S‐doping and Ag–Sn alloying enhance the CO 2 adsorption and improve the stability of *OCHO intermediate. This work offers a facile strategy for designing highly active and selective electrocatalyst for CO 2 RR.

CO2 hydrogenation to light olefins generally occurs via Fischer-Tropsch (FT) synthesis and methanol-intermediate routes. However, these two routes usually give low light olefin yields, although large numbers of catalysts have been fabricated. This results from the limitation of the Anderson-Schulz-Flory (ASF) law or the formation of initial C-C bond and hydrocarbon pool (HCP) species. To overcome these problems, a higher alcohol-intermediate route is developed here as these alcoholic products are rapidly dehydrated to light olefins. The designed Na-CuFeOx/H-GeAPO-34 composite shows CO2 conversion of 75.1% and light olefins selectivity in all products (including CO) of 48.7%, thus resulting in an unprecedentedly high yield of 36.6%. In situ spectroscopy and DFT calculation results reveal that the metallic copper (Cu) species not only promotes iron (Fe) species reduction and carbonization by overflowing active hydrogen species and transferring electrons but also provides an effective site for stabilizing nondissociative CO* species. This enhances formation of CHx* and nondissociative CO* species, which are coupled to generate large amounts of higher alcohols intermediates that are facilely dehydrated into light olefins on weakly acidic H-GeAPO-34. This work confirms that the higher alcohols-intermediate route is highly effective for converting CO2 into light olefins.

Iron-nitrogen-carbon (FeNC) catalysts represent promising alternatives to platinum-group metals for the oxygen reduction reaction (ORR) in energy conversion technologies. However, their operational stability remains a critical challenge. In this study, we unravel the distinct degradation mechanisms and active-site behaviors of FeNC catalysts under acidic and alkaline ORR conditions. Intriguingly, catalysts subjected to electrochemical cycling in acidic media but tested in alkaline conditions exhibit nearly preserved ORR activity, revealing that degradation pathways differ fundamentally between the two environments. With the help of density functional theory calculations, we identify Fe-centered sites as the primary active centers in acidic media, whereas under alkaline conditions─where hydroxyl adsorption passivates Fe sites─neighboring carbon atoms adjacent to nitrogen become the dominant active sites. The Mössbauer spectroscopy results show that under acidic cycling, pyrrolic nitrogen-coordinated Fe (S1) sites suffer a significant loss while the pyridinic nitrogen-coordinated Fe (S2) sites retain high stability. In contrast, during alkaline cycling, Fe site losses are minimal, while the carbon support undergoes more severe corrosion. By selectively engineering the Fe sites and carbon support, we experimentally validated the conclusions on the active sites. This work provides critical insights into the site-dependent durability of FeNC catalysts and underscores the necessity of tailored catalyst design for stable and efficient ORR across diverse operating conditions.