In this work, a series of highly porous and multifunctional CeSnO3/Bi2S3 perovskite-based heterojunctions (CBX) was successfully synthesized via a two-step mixing approach. Among them, the optimized 30% CeSnO3/Bi2S3 heterojunction (CB30) exhibited outstanding textural and electronic properties, featuring a high specific surface area (similar to 85 m2 g-1), which enabled efficient light harvesting and enhanced charge carrier separation. Consequently, CB30 degraded 70.7% of lindane (LN; 600 & micro;g L-1) in aqueous media under solar light irradiation within 100 min. The incorporation of peroxymonosulfate (PMS) into the reaction medium synergistically enhanced the photocatalytic efficiency of the CB30 heterojunction, achieving 93.2% degradation of LN in 100 min. The outstanding performance of CB30 in conjunction with PMS is primarily attributed to the successful activation of PMS by the oxygen-vacancy-rich CeSnO3/Bi2S3 heterojunction and the continuous redox recycling of Ce3+/Ce4+ species in the heterojunction. Furthermore, radical quenching experiments revealed hydroxyl, sulphate and superoxide radical ions ((OH)-O-center dot, SO4(center dot)- and O2(center dot)-) as the dominant species responsible for the photocatalytic degradation of LN in aqueous media. In addition to LN degradation, antimicrobial activity analysis tests confirmed the excellent performance of CB30, with an average zone of inhibition (ZOI) of 21.5 mm and 20 mm against Escherichia coli (E. coli) and Candida albicans (C. albicans), respectively. Furthermore, CB30 exhibited outstanding hydrogen evolution performance of 12.2, 22.2 and 37.7 mmol g-1 of H2 with external quantum efficiency (EQE) values of 34.4%, 41.9% and 50.5% upon simulated solar irradiation for 6, 9 and 12 h of reaction time, respectively. The superior photocatalytic and photo-electrochemical activities are primarily governed by the synergistic integration of step-scheme (S-scheme) charge transfer, oxygen vacancies (34.91%) and Ce3+/Ce4+ redox cycling, establishing CB30 as a robust and multifunctional platform for persistent pollutant degradation, antimicrobial disinfection and sustainable hydrogen production.

The introduction of oxygen vacancies (Ov) enables modulation of electronic structure and surface acidity/basicity of catalysts, leading to enhanced photocatalytic or thermocatalytic activity. However, the dynamic synergy between photothermal excitation and vacancy-engineered catalytic pathways remains unclear. Here, we constructed an Ov-rich Pt/TiO2-Ov catalyst, which exhibits high stability and a sixfold increase in propylene (C3H6) conversion compared to Pt/TiO2. This defective structure exhibits a reduced bandgap due to Ti 3d-Pt 5d orbital synergy. Experimental and calculated results demonstrate that the orbital synergy can trigger photothermal coupling and subsequently activate both molecular oxygen and lattice oxygen. Upon photothermal condition, Ov enhance the basic strength of nucleophilic lattice oxygen induced by Pt-O-Ti hybridization, which promotes cleavage of the methyl C-H bond in C3H6 and facilitates intermediate acrolein formation, thus accelerating C3H6 oxidation. Notably, Pt/TiO2-Ov demonstrates excellent C3H6 oxidation activity under ambient outdoor sunlight and is also effective against other common indoor pollutants such as methanol and toluene. This study reveals the effect of Ov on photothermal C3H6 oxidation and provides effective strategies for the rational design of advanced photothermal catalysts.

Microdroplet chemistry offers a promising platform for advancing green chemical processes; however, its limited reaction efficiency has restricted practical applications. Herein, we report a scalable iodide-mediated microdroplet system that markedly enhances stability and rate. The iodide-mediated microdroplet system (0.1 wt %) can achieve 100% ozone (O3) decomposition at the gas-liquid interface for 120 h and exhibits continuous and stable characteristics. Experiments proved that compared with bulk solution, I- enrichment and strong O3 affinity at microdroplet interfaces promote the accumulation of reactants and stabilize transition states. Moreover, the strong interfacial electric field induces hydroxide dissociation and drives electron-mediated regeneration of I- from iodine species, thereby sustaining continuous O3 reduction. Compared with the spray reactor, the iodide-mediated microdroplet reactor achieves a 100% O3 conversion, above 5-fold longer operational stability, 8.0% cost, and 10.4% energy consumption. Life cycle assessment further confirms its superior environmental and economic performance. This work provides a mechanistic understanding of the iodide-driven interfacial redox reaction and offers a scalable, green approach for O3 purification.

Light intensity regulates energy input and ecological balance in algal-bacterial symbiotic systems; however, underlying light-driven mechanisms remain unclear. This study explored microbial community succession, functional shifts, and metabolic regulation under light gradients in an algal-bacterial symbiotic system comprising microalgae, partial-nitrification, and anaerobic ammonium oxidation. Light intensity exhibited a dual effect. Optimal total nitrogen removal efficiency (TNRE) reached 91% at a light intensity of 280 ± 10 μmol/(m2·s), reflecting balanced algal-bacterial interactions. Higher light (380 ± 10 μmol/(m2·s)) induced excessive oxygen production and nitrite accumulation, thereby reducing TNRE to 76%. Ultra-high light (480 ± 10 μmol/(m2·s)) triggered algal photoinhibition, decreasing oxygen production and restoring TNRE to 88%. Microbial network stability declined with increasing light intensity but recovered under ultra-high light. Meanwhile, metabolism shifted significantly from purine and nucleotide metabolism to tryptophan metabolism (p < 0.05), reflecting a metabolic transition from proliferative growth to stress resistance. These findings demonstrate the intrinsic light-driven self-regulatory mechanism in autotrophic algal-bacterial systems.

Abstract Domestic waste generates volatile fatty acids (VFAs) and emits strong malodors that reduce environmental comfort. The generation of these odor-causing molecules usually occurs in relatively high-humidity conditions, which speed up the deterioration of adsorbents, creating secondary waste from frequent replacement. Herein, we report a lithium-doped manganese dioxide (Li–MnO2) photothermal system that sustainably degrades acetic acid (CH3COOH, a key VFA). Mechanistic studies reveal the ionic bond in Li–O localizes electrons at the oxygen atom, while the covalent bond in Mn–O establishes an efficient electron transport channel. This electron-rich oxygen can cleave the O–H bond in H2O with an ultra-low energy barrier of 0.01 eV, generating dihydroxy groups, which subsequently initiate a nucleophilic attack on the O–H and C–H bonds in CH3COOH molecules. The introduction of light not only efficiently converts the material surface into thermal energy, but it also triggers electron rearrangement. The engineered Li–MnO2 catalyst demonstrates complete CH3COOH degradation at 291 mW cm–2. A modular photothermal purification device demonstrates above 1000 h odor removal efficiency in municipal waste scenario. We anticipate this work will enable perpetual CH3COOH removal from domestic waste without external energy input, offering a sustainable solution for odor control in waste management.

The construction of a built-in electric field and precise modulation of active sites are pivotal for enhancing the efficiency of catalytic reactions, yet achieving synergistic enhancement through a simple modification remains a challenge. Herein, we report a facile NaSCN assisted thermal treatment strategy to graft cyano groups onto the terminal amino sites of g-C3N4 (CN). The introduced cyano groups not only enhance the intrinsic polarization of the material, as confirmed by a 1.83-fold increase in the dipole moment and a superior piezoelectric coefficient (d33 = 67.2 pm/V), but also create a strong internal electric field that synergizes with the piezoelectric field to promote charge separation and transfer. Consequently, the optimized NHCN-3 catalyst achieves an outstanding piezo-photocatalytic H2O2 generation rate of 158.2 mM/g/h, which is 22.6 times greater than that of CN. Moreover, combined in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) and density functional theory (DFT calculations) indicate a dual-site reaction mechanism: the terminal carbon atom adjacent to the grafted cyano group in the modified material reduces the energy barrier for H2O cleavage into the *OH intermediate, while the neighboring -NH- group promotes the reaction by adsorbing a hydrogen atom and transforming into -NH2 + species. This research provides new ideas for the multi-site cooperative effect and regulation of the H2O2 reaction pathway, laying the foundation for the design of high-performance piezophotocatalysts.

In this work, a series of highly porous and multifunctional CeSnO 3 /Bi 2 S 3 perovskite-based heterojunctions (CBX) was successfully synthesized via a two-step mixing approach.

The integration of membrane separation with heterogeneous advanced oxidation processes is a prospective strategy for the elimination of contaminants during wastewater treatment. Fe-based catalysts and the green oxidant peracetic acid (PAA) are desirable candidates for the development of catalytic membranes because they are environmentally friendly. However, the construction of catalytic ceramic membranes (CMs) modified with efficient Fe-based catalysts that generate increased amounts of high-valent Fe-O species during PAA activation for the degradation of specific pollutants, especially during instantaneous membrane filtration, remains challenging. Herein, a single-atom Fe-based catalytic CM was fabricated and further optimized via the "electron enrichment + electron-transfer enhancement" method, which specifically refers to the simultaneous introduction of nitrogen vacancy (Nv) defects and the construction of ultrathin nanostructures. The CM-UCNv-Fe/PAA system exhibited outstanding bisphenol A (BPA) removal performance, with a first-order rate constant of 0.078 ms-1 (4680 min-1), which was 37 times greater than that of CM-BCN-Fe/PAA system (126 min-1). In addition, the remarkable environmental adaptability, stability and low Fe leakage underscored its practical application potential. Mechanistic investigations revealed that Fe(V)=O was the predominant reactive oxygen species. Multi-scaled characterization and theoretical calculations confirmed that engineered Nv defects facilitated the construction of electron-rich single-atom Fe sites, which had the potential to supply more electrons. Porous ultrathin nanosheets exposed more Fe active sites, and many microinterfaces within the catalytic layers of the CM increased the possibility of contact between the Fe sites and PAA. The synergy of them enabled intensive electron transfer from Fe sites to PAA, which was the driving force for Fe(V)=O conversion during transient membrane filtration. In addition, the efficacy of the catalytic CM in municipal wastewater treatment and membrane fouling control were investigated. This work expands the research on the intensive electron transfer of a single-atom Fe-based catalytic CM for increased Fe(V)=O conversion via Nv defect introduction and ultrathin nanostructure construction.

The integration of ozone with ceramic membrane offers a promising approach for treating algae-laden water but presents challenges in balancing oxidation efficacy with the preservation of cell integrity. In this study, catalytic ceramic membrane system embedded with zirconium (Zr) developed achieved 58.4 % removal of 2-methylisoborneol and 68.2 % removal of geosmin through dehydration and ring opening via hydroxyl radical-mediated degradation pathways generated in situ on the membrane under optimal ozone dosage. It is worth noting that the mild ozone concentration increased the hydrophobic interaction energy between algal cells and the filter cake layer from -13.7 mJ/m2 to -0.3 mJ/m2, thereby effectively reducing the deposition of pollutants on the membrane. By controlling oxidative intensity, the ceramic membrane's reversible and irreversible resistances were decreased by 86.7 % and 80.1 %, respectively, while maintaining >95 % algal cell integrity. This study establishes a mild catalytic oxidation paradigm for ceramic membrane-based algae-laden water treatment, achieving simultaneous degradation of odorants and membrane fouling control.

Platinum-group metals (Pt) commonly used in thermal catalytic processes often suffer from catalyst deactivation, such as Pt sintering, Pt overoxidation, and Pt loss under high-temperature conditions. To address these, we present a novel PtSA/CeZrO2 catalyst, featuring isolated Pt single atoms (PtSA) on a Ce0.8Zr0.2O2 support with an ordered macroporous (OM) structure. Firstly, Zr-stabilized dynamic low-coordinated PtSA releases more free d-electrons by reducing Pt-O bond occupation, thereby preserving peroxide activity at high temperatures and enhancing propane C-H activation. Additionally, the OM structure prevents Pt loss and reduces Pt loading to 0.4 gPt/L, compared with 0.9 gPt/L in commercial diesel oxidation catalysts. As a result, the PtSA/CeZrO2 maintains 92% conversion at 450 °C even after 50 h aging at 800 °C with 10 vol.% H2O. Finally, the catalyst is integrated into a 3.4-liter commercial cordierite monolith for developing and scaling robust catalytic converters.

Effective generation of H+ and OH- in the Fenton by electrodes is crucial for addressing the impact of acidity and alkalinity on the environment. In this study, electrolysis was coupled with membrane Fenton for nanofiltration concentrate treatment and membrane fouling behaviors were investigated. The effects of current density and dosage (H2O2 and Fe2+ ) were studied. According to the Box-Behnken design results, both current density and the dosages of H2O2 and Fe2+ positively influenced the removal of organic pollutants, with the former showing the most significant effect. Hydroxyl radical (center dot OH) oxidized the organic pollutants into intermediates, realizing a removal efficiency of 74.50 %. The anode oxidation and Fenton process effectively degraded fluorescent components, particularly humic acid-like substances. Ammonia nitrogen was degraded by active chlorine produced at the anode, with an average removal rate of 51.36 %. Additionally, an increase in current density enhanced ion exchange membrane fouling. Chemical composition analysis suggested that the membrane was primarily covered with hydroxide crystal substances. The ultrafiltration (UF) membrane analysis indicated that cake layer formation was responsible for the trans-membrane pressure (TMP) increase, and cake-complete was the primary mechanism contributing to UF membrane fouling. The membrane Fenton process without acid-base agents exhibits significant potential for contaminants removal from nanofiltration concentrate and is advantageous for cleaning membrane fouling.

Emissions from industrial activities have led to the significant accumulation of volatile organic compounds (VOCs) in the atmosphere, raising substantial concerns due to their serious threats to human health and the global environment in recent years. Among the various strategies for VOC abatement, adsorption technology has emerged as a promising approach for effectively removing VOCs from contaminated air. However, the adsorption behavior and mechanisms for different VOC species remain poorly understood. Herein, the adsorption characteristics of eight typical VOC categories (C <= 8 atoms) commonly emitted by the petrochemical industry were systematically investigated using density functional theory (DFT) calculations at the electronic and atomic levels on monolayer MoS2. The VOC categories analyzed include alkanes, alkenes, alkynes, alcohols, aldehydes, carboxylic acids, ketones and aromatic hydrocarbons. Our research was aimed at investigating the adsorption behaviors of various types of VOCs, including those with varying carbon chain lengths within the same category. Results demonstrated that the unique structural properties of the MoS(2 )monolayer not only provided excellent adsorption capabilities but also exhibited distinct responses to the eight aforementioned VOC categories. The adsorption energies of the VOCs followed a distinct hierarchical order, alkanes < aromatic hydrocarbons < alkynes < aldehydes < ketones < alkenes < alcohols < carboxylic acids, with the values ranging from -0.25 to -1.19 eV. In different VOC adsorption systems, the distance between the rightmost peak of the density of states (DOS) and the Fermi level ranged from -1.42 to -0.17 eV. Additionally, for a given VOC category, it was observed that an increase in carbon chain length correlated with an increase in adsorption energy. A predictive fitting curve for the adsorption energy of VOCs was derived and expressed as Eads (Ev) = -0.13X - 0.12, where X represents the number of carbon atoms. Through comprehensive analyses involving charge density differences, DOS and Mulliken charge analysis, the underlying mechanisms correlating adsorption energy with both VOC species and carbon chain length were elucidated. Our research highlights the potential of MoS(2 )as a promising candidate for selective VOC adsorption and provides a theoretical framework for the development of high-performance VOC adsorbents.

To overcome the low efficiency, high cost and less environmentally friendly limitations in existing textile wastewater disposal technology, an innovative approach of cation exchange membrane electrolysis coupled with magnesium salt precipitation (CEM-MSP) was implemented. This method simultaneously achieved the high-efficiency adsorption decolorization of dyes and the recovery of lye. The results indicated that cation exchange membrane electrolysis with MgSO4 added to the anode chamber (CEM-EA) exhibited excellent decolorization performance on DB86 dye and achieved low residual Mg2+ concentration. Furthermore, the adsorption mechanism of Mg(OH)2 on DB86 was systematically investigated. The adsorption process fitted with the first-order kinetic, where the adsorption of DB86 by Mg(OH)2 was dominated by electrostatic attraction. Detailed comparison of the four systems demonstrated that CEM-EA was superior to the single magnesium addition method (85.24%) or the stand-alone membrane electrolysis method (10.36%), with 99% decolorization efficiency. In comparison to the cation exchange membrane electrolysis with MgSO4 added to the cathode chamber (CEM-EC), the CEM-EA could diminish the Mg2+ concentration in the effluent to facilitate the lye recovery while guaranteeing the decolorization efficiency. In addition, the DB86 adsorption behavior during the formation of Mg(OH)2 in the cathode chamber was investigated. The Mg(OH)2 particles were relatively dense copper-blue agglomerates with a thin lamellar layer on the surface. Notably, only slight mass contamination was observed on the cation exchange membrane (CEM) surface after multiple cycles. Minor CEM contamination illustrated the stable treatment efficiency of the CEM-EA after several cycles. This study constructed a novel approach integrating membrane electrolysis with magnesium salt precipitation, delivering valuable technical solutions for textile wastewater disposal.

Microalgae, ammonia-oxidizing bacteria (AOB), and anaerobic ammonium-oxidizing bacteria (AnAOB) have been proven to form an integrated algal-bacterial biofilm system with over 93 % of total nitrogen removal. Compared to conventional nitrification-denitrification process, this system operated without additional organic carbon or aeration. In order to understand the interaction mechanisms between bacteria and algae, this study investigated microbial community succession, the changes in metabolic pathways and the potential role of acyl-homoserine lactone (AHL)-mediated quorum sensing (QS) during the formation of the algae/partial nitrification/anammox biofilm system. Within this algal-bacterial symbiotic biofilm, the dominant genera identified were Candidatus_Brocadia (AnAOB), Nitrosomonas (AOB), and Geitlerinema (microalgae), with relative abundances of 13.86 %, 6.37 %, and 2.88 %, respectively. Compared with the first two stages, the abundance of genes related to nitrogen metabolism pathways (anaerobic ammonium oxidation, denitrification, and ammonia assimilation) increased, indicating enhanced nitrogen transformation capacity in the algal-bacterial symbiotic stage. Co-occurrence network analysis also revealed enhanced microbial interactions, with increased negative correlations (from 36.07 % to 39.38 %), high average standard betweenness centrality (from 0.193 to 0.304), and reduced community vulnerability (from 0.037 to 0.028), contributing to biofilm stability and resilience. The variations in AHLs provided direct evidence for more frequent interspecies communication, facilitating the ecological reconfiguration in the biofilm. Overall, the close synergistic relationship between microalgae and bacteria supports stable biofilm development and high nitrogen removal efficiency.

A three-dimensional bioelectrochemical system was developed by coupling self-corrosive Fe/C microelectrodes with a membrane-aerated electroactive biofilm reactor (IC-MAEBR) to enhance antibiotic and antibiotic resistance gene (ARG) reduction. The IC-MAEBR significantly enriched aromatic proteins as dominant fluorescent components in cathode biofilms, while exhibiting an elevated α-helix to (β-sheet + random coil) (62.8%), enhanced biofilm density. Besides, the coordinated action of applied potential and microelectrolysis reduced sul1 and sul2 abundances in cathode biofilms by -2.6 log2 and -1.6 log2, respectively, primarily through host microorganism inactivation. Although higher potential differences (0.75 V) narrowed SMX removal difference between membrane-aerated electroactive biofilm reactors (MAEBR) and IC-MAEBR, IC-MAEBR demonstrated superior performance at lower potentials (0.5 V), achieving rapid SMX degradation within 12 h and maintained accelerated removal kinetics even post-discharge cycles, outperforming MABR and MAEBR by 4.2 μg/L/h and 9.7 μg/L/h, respectively. This study provides new insights into microelectrolysis enhanced electroactive-biofilm in antibiotics and ARGs removal.

We investigated the catalytic activity of multi-N-doped graphene substrates as electrocatalysts for the oxygen reduction reaction (ORR) using first-principles methods. The six multi-N-doped configurations studied are all thermodynamically stable, with formation energies indicating that N impurity atoms tend to be dispersed. The catalytic sites for ORR on the substrates are multiple, with significant differences in the adsorption energies of the adsorbates. The most stable adsorption sites are positively charged carbon atoms, where the charge and net spin magnetic moment at the adsorption sites enhance the adsorption of the adsorbates. However, the most stable adsorption sites generally exhibit overly strong adsorption of oxygen, making hydrogenation difficult and hindering the continuous progression of the ORR. For substrates with pre-adsorbed oxygen, the change in the substrate's electronic structure weakens the adsorption of the adsorbates, thereby reducing the ORR overpotential and making the ORR more feasible, with the rate-determining step typically becoming the hydrogenation of *O2. By comparing the ORR performance across various substrates, we found that the optimal overpotential for ORR on multi-N-doped graphene substrates ranges from 0.76 to 0.88 V. The kinetic process of ORR indicates that multi-N-doped graphene with pre-adsorbed O atoms significantly enhances the ORR catalytic activity compared to single-N-doped graphene.

For the remediation of pharmaceuticals and personal care products (PPCPs), the carbonaceous catalyst/peracetic acid (PAA)-based metal-free advanced oxidation process has gained increasing interest. In this study, graphdiyne (GDY), an emerging two-dimensional carbon catalyst featuring both sp- and sp2-hybridized carbon atoms, was utilized to activate PAA in order to degrade acetaminophen (ACE). The efficacy of GDY-mediated PAA oxidation towards pollutants surpasses those of common carbon materials. Specifically, it is four times better than that of the graphene/PAA system. The GDY/PAA system has strong stability and resistance to interference from ions in ACE degradation, showing excellent degradation effects over a wide pH range (pH 5-9), endowing it with broad prospects for practical application. The sp2-/sp-hybridized structure of GDY improves the oxidation efficiency of ACE, and the sp2-C (benzene ring) and the it-electron delocalization regions on GDY are identified as the active sites. The GDY-PAA* complex generated from a non-radical electron-transfer process (ETP) was demonstrated as the dominant active species. We systematically studied the degradation of typical PPCPs by the GDY/PAA system, gaining new insights into the GDY application in the field of water remediation.

Radiative cooling has emerged as a promising technique for reducing energy consumption in building thermal management due to its passive cooling property and no external energy requirement. Despite significant advances, scalable production of artificial photonic radiators with periodic structures, environmental stability, high radiative cooling performance, and economic applicability is still challenging in most state-of-the-art radiative coolers. Rational structure and materials design are essential to promote daytime sunlight reflectance while maintaining a high emissivity within the atmospheric window (8-13 µm). In this work, inspired from the unique hair structure of heat-resistant organisms, a biomimetic micro-pyramid shaped structure model is analyzed. By mimicking the intricate design with a silicon template, a radiative cooling film containing specialized micro-pyramid structure is fabricated by integrating high dielectric constant materials with polymers and receiving PVDF coating. The resulting film boasts a solar reflectance of 97.3% and an exceeding 98% infrared light emission within the atmospheric window. In addition, silicon rubber endows this membrane with strong tensile and rebound properties while surficial hydrophobicity protects the membrane from dust infestation. Considering the manufacturing simplicity and cost-effectiveness, this method shows great potential for mass production, shedding light on building thermal management.

Residual aluminum (Al) is a growing pollutant in nanofiltration (NF) membrane-based drinking water treatment. To investigate the impact of distinct Al species fouling layers on gypsum scaling during NF, gypsum scaling tests were conducted on bare and three Al-conditioned (AlCl3-, Al13, and Al30-) membranes. The morphology of gypsum, the role of Al species on Ca2+ adsorption during gypsum scaling, and the interactions between gypsum crystals and Al-conditioned membranes were investigated. Results indicated that Al-conditioned membranes had lower flux decline than the bare membrane, with the order of AlCl3-<Al30-<Al13-conditioned membrane, due to a lower heterogeneous crystallization tendency. The membrane surface charge was the major factor determining heterogeneous crystallization. Based on the analyses of quartz crystal microbalance with dissipation (QCM-D), it was found that surface Al species inhibited the adsorption of Ca2+ on the membrane surface thereby mitigating heterogeneous crystallization. FTIR further indicated that this inhibition was due to the competition between Al species and Ca2+ for binding sites on the membrane surface. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analyses showed that Al-conditioned membranes had a higher gypsum adhesion tendency than the bare membrane, and hydrophobic attraction dominated the interaction. This study provides new insights into how residual Al species impact mineral scaling during NF.

The incorporation of metal single atoms into carbon nitride (CN) has emerged as a promising strategy for photocatalytic CO₂ reduction under visible light. However, achieving high single‐atom loading and unraveling the precise role of active metal centers in CO₂ conversion remain formidable challenges. Herein, an ultrasound‐assisted coordination exchange strategy is reported that enables the high‐loading of Cu single atoms on CN. X‐ray absorption near‐edge spectroscopy and aberration‐corrected electron microscopy confirm that Cu is atomically dispersed and coordinated with nitrogen. The introduction of Cu single atoms modulates the electronic structure of CN, serving as electron accumulation centers that facilitate charge carrier separation and transfer. Theoretical calculations combined with in situ spectroscopic analyses reveal that Cu single atoms act as active sites, enhancing CO₂ adsorption and activation while significantly reducing the energy barrier for * COOH formation, thereby optimizing reaction thermodynamics. As a result, under visible‐light irradiation, Cu‐modified CN achieves a CO production rate of 14.65 µmol g⁻¹ h⁻¹, representing an 11.3‐fold enhancement over pristine CN. This work not only establishes an efficient approach for synthesizing high‐loading single‐atom catalysts but also provides fundamental insights into the mechanistic role of single‐atom sites in photocatalytic CO₂ reduction.