Temperature-Induced Low-Coordinate Ni Single-Atom Catalyst for Boosted CO2 Electroreduction Activity

Single-atom catalysts (SACs) exhibit remarkable potential for electrochemical reduction of CO₂ to value-added products. However, the commonly pursued methods for preparing SACs are hard to scale up, and sometimes, lack general applicability because of expensive raw materials and complex synthetic procedures. In addition, the fine tuning of coordination environment of SACs remains challenging due to their structural vulnerability. Herein, a simple and universal strategy is developed to fabricate Ni SACs with different nitrogen coordination numbers through one-step pyrolysis of melamine, Ni(NO₃)∙6H₂O, and polyvinylpyrrolidone at different temperatures. Experimental measurements and theoretical calculations reveal that the low-coordinate Ni SACs exhibit outstanding CO₂ reduction performance and stability, achieving a Faradic efficiency (FE_CO) of 98.5% at −0.76 V with CO current density of 24.6 mA cm⁻², and maintaining FE_CO of over 91.0% at all applied potential windows from −0.56 to −1.16 V, benefiting from its coordinatively unsaturated structure to afford high catalytic activity and low barrier for the formation of *COOH intermediate. No significant performance degradation is observed over 50 h of continuous operation. Additionally, several other metallic single-atom catalysts are successfully prepared by this synthetic method, demonstrating the universality of this strategy.     

Promoting CO2 Dynamic Activation via Micro-Engineering Technology for Enhancing Electrochemical CO2 Reduction

Optimizing the coordination structure and microscopic reaction environment of isolated metal sites is promising for boosting catalytic activity for electrocatalytic CO₂ reduction reaction (CO₂RR) but is still challenging to achieve. Herein, a newly electrostatic induced self-assembly strategy for encapsulating isolated Ni-C₃N₁ moiety into hollow nano-reactor as I-Ni SA/NHCRs is developed, which achieves FE_CO of 94.91% at −0.80 V, the CO partial current density of ≈−15.35 mA cm⁻², superior to that with outer Ni-C₂N₂ moiety (94.47%, ≈−12.06 mA cm⁻²), or without hollow structure (92.30%, ≈−5.39 mA cm⁻²), and high FE_CO of ≈98.41% at 100 mA cm⁻² in flow cell. COMSOL multiphysics finite-element method and density functional theory (DFT) calculation illustrate that the excellent activity for I-Ni SA/NHCRs should be attributed to the structure-enhanced kinetics process caused by its hollow nano-reactor structure and unique Ni-C₃N₁ moiety, which can enrich electron on Ni sites and positively shift d-band center to the Fermi level to accelerate the adsorption and activation of CO₂ molecule and *COOH formation. Meanwhile, this strategy also successfully steers the design of encapsulating isolated iron and cobalt sites into nano-reactor, while I-Ni SA/NHCRs-based zinc-CO₂ battery assembled with a peak power density of 2.54 mW cm−⁻² is achieved.     

Geometric and Electronic Structural Engineering of Isolated Ni Single Atoms for a Highly Efficient CO2 Electroreduction

Tuning the coordination environment and geometric structures of single atom catalysts is an effective approach for regulating the reaction mechanism and maximize the catalytic efficiency of single-atom centers. Here, a template-based synthesis strategy is proposed for the synthesis of high-density NiN_x sites anchored on the surface of hierarchically porous nitrogen-doped carbon nanofibers (Ni-HPNCFs) with different coordination environments. First-principles calculations and advanced characterization techniques demonstrate that the single Ni atom is strongly coordinated with both pyrrolic and pyridinic N dopants, and that the predominant sites are stabilized by NiN₃ sites. This dual engineering strategy increases the number of active sites and utilization efficiency of each single atom as well as boosts the intrinsic activity of each active site on a single-atom scale. Notably, the Ni-HPNCF catalyst achieves a high CO Faradaic efficiency (FE_CO) of 97% at a potential of −0.7 V, a high CO partial current density (j_CO) of 49.6 mA cm⁻² (−1.0 V), and a remarkable turnover frequency of 24 900 h⁻¹ (−1.0 V) for CO₂ reduction reactions (CO₂RR). Density functional theory calculations show that compared to pyridinic-type NiN_x, the pyrrolic-type NiN₃ moieties display a superior CO₂RR activity over hydrogen evolution reactions, resulting in their superior catalytic activity and selectivity.     

Gas Diffusion Strategy for Inserting Atomic Iron Sites into Graphitized Carbon Supports for Unusually High-Efficient CO2 Electroreduction and High-Performance Zn–CO2 Batteries

Emerging single-atom catalysts (SACs) hold great promise for CO₂ electroreduction (CO₂ER)_, but the design of highly active and cost-efficient SACs is still challenging. Herein, a gas diffusion strategy, along with one-step thermal activation, for fabricating N-doped porous carbon polyhedrons with trace isolated Fe atoms (Fe₁NC) is developed. The optimized Fe₁NC/S₁-1000 with atomic Fe-N₃ sites supported by N-doped graphitic carbons exhibits superior CO₂ER performance with the CO Faradaic efficiency up to 96% at −0.5 V, turnover frequency of 2225 h⁻¹, and outstanding stability, outperforming almost all previously reported SACs based on N-doped carbon supported nonprecious metals. The observed excellent CO₂ER performance is attributed to the greatly enhanced accessibility and intrinsic activity of active centers due to the increased electrochemical surface area through size modulation and the redistribution of doped N species by thermal activation. Experimental observations and theoretical calculations reveal that the Fe-N₃ sites possess balanced adsorption energies of *COOH and *CO intermediates, facilitating CO formation. A universal gas diffusion strategy is used to exclusively yield a series of dimension-controlled carbon-supported SACs with single Fe atoms while a rechargeable Zn–CO₂ battery with Fe₁NC/S₁-1000 as cathode is developed to deliver a maximal power density of 0.6 mW cm⁻².     

Ultrathin Nitrogen-Doped Carbon Encapsulated Ni Nanoparticles for Highly Efficient Electrochemical CO2 Reduction and Aqueous Zn-CO2 Batteries

Electrochemical CO₂ reduction reaction (CO₂RR), powered by renewable electricity, has attracted great attention for producing high value-added fuels and chemicals, as well as feasibly mitigating CO₂ emission problem. Here, this work reports a facile hard template strategy to prepare the Ni@N-C catalyst with core–shell structure, where nickel nanoparticles (Ni NPs) are encapsulated by thin nitrogen-doped carbon shells (N-C shells). The Ni@N-C catalyst has demonstrated a promising industrial current density of 236.7 mA cm⁻² with the superb FE_CO of 97% at −1.1 V versus RHE. Moreover, Ni@N-C can drive the reversible Zn-CO₂ battery with the largest power density of 1.64 mW cm⁻², and endure a tough cycling durability. These excellent performances are ascribed to the synergistic effect of Ni@N-C that Ni NPs can regulate the electronic microenvironment of N-doped carbon shells, which favor to enhance the CO₂ adsorption capacity and the electron transfer capacity. Density functional theory calculations prove that the binding configuration of N-C located on the top of Ni slabs (Top-Ni@N-C) is the most thermodynamically stable and possess a lowest thermodynamic barrier for the formation of COOH^* and the desorption of CO. This work may pioneer a new method on seeking high-efficiency and worthwhile electrocatalysts for CO₂RR and Zn-CO₂ battery.     

Enhanced the Efficiency of Electrocatalytic CO2-to-CO Conversion by Cd Species Anchored into Metal-Organic Framework

Metal-organic frameworks (MOFs) as a promising platform for electrocatalytic CO₂ conversion are still restricted by the low efficiency or unsatisfied selectivity for desired products. Herein, zirconium-based porphyrinic MOF hollow nanotubes with Cd sites (Cd-PCN-222HTs) are reported for electrocatalytic CO₂-to-CO conversion. The dispersed Cd species are anchored in PCN-222HTs and coordinated by N atoms of porphyrin structures. It is discovered that Cd-PCN-222HTs have glorious electrocatalytic activity for selective CO production in ionic liquid-water (H₂O)-acetonitrile (MeCN) electrolyte. The CO Faradaic efficiency (FE_CO) of >80% could be maintained in a wide potential range from −2.0 to −2.4 V versus Ag/Ag⁺, and the maximum current density could reach 68.0 mA cm⁻² at −2.4 V versus Ag/Ag⁺ with a satisfied turnover frequency of 26 220 h⁻¹. The enhanced efficiency of electrocatalytic CO₂ conversion of Cd-PCN-222HTs is closely related to its hollow structure, anchored Cd species, and good synergistic effect with electrolyte. The density functional theory calculations indicate that the dispersed Cd sites anchored in PCN-222HTs not only favor the formation of *COOH intermediate but also hinder the hydrogen evolution reaction, resulting in high activity of electrocatalytic CO₂-to-CO conversion.     

Revealing the Kinetic Balance between Proton-Feeding and Hydrogenation in CO2 Electroreduction

Electrocatalytic reduction of CO₂ to high-value-added chemicals provides a feasible path for global carbon balance. Herein, the fabrication of Ni_NPx@Ni_SAy-NG (x,y = 1, 2, 3; NG = nitrogen-doped graphite) is reported, in which Ni single atom sites (Ni_SA) and Ni nanoparticles (Ni_NP) coexist. These Ni_NPx@Ni_SAy-NG presented a volcano-like trend for maximum CO Faradaic efficiency (FE_CO) with the highest point at Ni_NP2@Ni_SA2-NG in CO₂RR. Ni_NP2@Ni_SA2-NG exhibited ≈98% of maximum FE_CO and a large current density of −264 mA cm⁻² at −0.98 V (vs. RHE) in the flow cell. In situ experiment and density functional theory (DFT) calculations confirmed that the proper content of Ni_SA and Ni_NP balanced kinetic between proton-feeding and CO₂ hydrogenation. The Ni_NP in Ni_NP2@Ni_SA2-NG promoted the formation of H* and reduced the energy barrier of *CO₂ hydrogenation to *COOH, and CO desorption can be efficiently facilitated by Ni_SA sites, thereby resulting in enhanced CO₂RR performance.     

Boron bridged NiN4B2Cx single-atom catalyst for superior electrochemical CO2 reduction

Single-atom nickel catalysts hold great promise in the application of electrocatalytic carbon dioxide reduction reaction (CO₂RR), but suffer from the sluggish kinetics and serious competitive hydrogen evolution reaction (HER), which restrict their overall catalytic performance. Herein, we report a boron-bridging strategy to manipulate the atomic coordination structure and construct a single-atom nickel catalyst with an active center of NiN₄B₂ to realize excellent CO₂RR performance. Density functional theory analysis suggests that the unique NiN₄B₂ sites with tuned electronic structure facilitate the adsorption of CO₂ molecules and effectively suppress the HER pathway by increasing corresponding energy barrier. As-obtained Ni-SAs@BNC catalyst with a NiN₄B₂ structure exhibits significantly enhanced catalytic activity and selectivity than commonly used single-atom nickel catalysts with a NiN₄ structure, especially at high applied potentials. A high current density of up to (214 ± 21) mA cm⁻² at a potential of −1.2 V with a high CO Faraday efficiency (FE_CO) of ∼97% was achieved in a flow cell. This work inspires new insights into the rational design of atomic coordination structure of single-atom catalysts with tunable electronic structure for superior electrocatalytic activities.     

Regulating the Electronic Structure of Bismuth Nanosheets by Titanium Doping to Boost CO2 Electroreduction and Zn–CO2 Batteries

The electrochemical carbon dioxide reduction reaction (E-CO₂RR) to formate is a promising strategy for mitigating greenhouse gas emissions and addressing the global energy crisis. Developing low-cost and environmentally friendly electrocatalysts with high selectivity and industrial current densities for formate production is an ideal but challenging goal in the field of electrocatalysis. Herein, novel titanium-doped bismuth nanosheets (Ti Bi NSs) with enhanced E-CO₂RR performance are synthesized through one-step electrochemical reduction of bismuth titanate (Bi₄Ti₃O₁₂). We comprehensively evaluated Ti Bi NSs using in situ Raman spectra, finite element method, and density functional theory. The results indicate that the ultrathin nanosheet structure of Ti Bi NSs can accelerate mass transfer, while the electron-rich properties can accelerate the production of *CO₂⁻ and enhance the adsorption strength of *OCHO intermediate. The Ti Bi NSs deliver a high formate Faradaic efficiency (FE_formate) of 96.3% and a formate production rate of 4032 µmol h⁻¹ cm⁻² at −1.01 V versus RHE. An ultra-high current density of −338.3 mA cm⁻² is achieved at −1.25 versus RHE, and simultaneously FE_formate still reaches more than 90%. Furthermore, the rechargeable Zn–CO₂ battery using Ti Bi NSs as a cathode catalyst achieves a maximum power density of 1.05 mW cm⁻² and excellent charging/discharging stability of 27 h.     

Highly Efficient Electroreduction of CO2 on Nickel Single‐Atom Catalysts: Atom Trapping and Nitrogen Anchoring

Construction of single atom catalysts (SACs) with high activity toward electroreduction of CO₂ still remains a great challenge. A very simple and truly cost‐effective synthetic strategy is proposed to prepare SACs via a impregnation–pyrolysis method, through one‐step pyrolysis of graphene oxide aerogel. Compared with other traditional methods, this process is fast and free of repeated acid etching, and thus it has great potential for facile operation and large‐scale manufacturing. Both X‐ray absorption fine structure and high‐angle annular dark‐field scanning transmission electron microscopy images confirm the presence of isolated nickel atoms, with a high Ni loading of ≈2.6 wt%. The obtained 3D porous Ni‐ and N‐codoped graphene aerogel exhibits excellent activity toward electroreduction of CO₂ to CO, in particular exhibiting a remarkable CO Faradaic efficiency of 90.2%. Density functional theory calculations reveal that free energies for the formation of intermediate *COOH on coordinatively unsaturated Ni? N sites are significantly lower than that on Ni? N₄ site, suggesting the outstanding activities of CO₂ electroreduction originate from coordinatively unsaturated Ni? N sites in catalysts.     

Enhanced CO Affinity on Cu Facilitates CO2 Electroreduction toward Multi-Carbon Products

Electrochemical CO₂ reduction reaction (CO₂RR) is a promising strategy for waste CO₂ utilization and intermittent electricity storage. Herein, it is reported that bimetallic Cu/Pd catalysts with enhanced *CO affinity show a promoted CO₂RR performance for multi-carbon (C2+) production under industry-relevant high current density. Especially, bimetallic Cu/Pd-1% catalyst shows an outstanding CO₂-to-C2+ conversion with 66.2% in Faradaic efficiency (FE) and 463.2 mA cm⁻² in partial current density. An increment in the FE ratios of C2+ products to CO  for Cu/Pd-1% catalyst further illuminates a preferable C2+ production. In situ Raman spectra reveal that the atop-bounded CO is dominated by low-frequency band CO on Cu/Pd-1% that leads to C2+ products on bimetallic catalysts, in contrast to the majority of high-frequency band CO on Cu that favors the formation of CO. Density function theory calculation confirms that bimetallic Cu/Pd catalyst enhances the *CO adsorption and reduces the Gibbs free energy of the C C coupling process, thereby favoring the formation of C2+ products.     

Cu?C(O) Interfaces Deliver Remarkable Selectivity and Stability for CO2 Reduction to C2+ Products at Industrial Current Density of 500 mA cm−2

The electrocatalytic CO₂ reduction reaction (CO₂RR) is an attractive technology for CO₂ valorization and high-density electrical energy storage. Achieving a high selectivity to C₂₊ products, especially ethylene, during CO₂RR at high current densities (>500 mA cm⁻²) is a prized goal of current research, though remains technically very challenging. Herein, it is demonstrated that the surface and interfacial structures of Cu catalysts, and the solid–gas–liquid interfaces on gas-diffusion electrode (GDE) in CO₂ reduction flow cells can be modulated to allow efficient CO₂RR to C₂₊ products. This approach uses the in situ electrochemical reduction of a CuO nanosheet/graphene oxide dots (CuO C(O)) hybrid. Owing to abundant Cu O C interfaces in the CuO C(O) hybrid, the CuO nanosheets are topologically and selectively transformed into metallic Cu nanosheets exposing Cu(100) facets, Cu(110) facets, Cu[n(100) × (110)] step sites, and Cu⁺/Cu⁰ interfaces during the electroreduction step,  the faradaic efficiencie (FE) to C₂₊ hydrocarbons was reached as high as 77.4% (FE_ethylene ≈ 60%) at 500 mA cm⁻² . In situ infrared spectroscopy and DFT simulations demonstrate that abundant Cu⁺ species and Cu⁰/Cu⁺ interfaces in the reduced CuO C(O) catalyst improve the adsorption and surface coverage of *CO on the Cu catalyst, thus facilitating C C coupling reactions.     

MOF-Derived In2O3/CuO p-n Heterojunction Photoanode Incorporating Graphene Nanoribbons for Solar Hydrogen Generation

Solar-driven photoelectrochemical (PEC) water splitting is a promising approach toward sustainable hydrogen (H₂) generation. However, the design and synthesis of efficient semiconductor photocatalysts via a facile method remains a significant challenge, especially p-n heterojunctions based on composite metal oxides. Herein, a MOF-on-MOF (metal-organic framework) template is employed as the precursor to synthesize In₂O₃/CuO p-n heterojunction composite. After incorporation of small amounts of graphene nanoribbons (GNRs), the optimized PEC devices exhibited a maximum current density of 1.51 mA cm⁻² (at 1.6 V vs RHE) under one sun illumination (AM 1.5G, 100 mW cm⁻²), which is approximately four times higher than that of the reference device based on only In₂O₃ photoanodes. The improvement in the performance of these hybrid anodes is attributed to the presence of a p-n heterojunction that enhances the separation efficiency of photogenerated electron-hole pairs and suppresses charge recombination, as well as the presence of GNRs that can increase the conductivity by offering better path for electron transport, thus reducing the charge transfer resistance. The proposed MOF-derived In₂O₃/CuO p-n heterojunction composite is used to demonstrate a high-performance PEC device for hydrogen generation.     

A Carbon-Free and Free-Standing Cathode From Mixed-Phase TiO2 for Photo-Assisted Li–CO2 Battery

Li–CO₂ battery provides a new strategy to simultaneously solve the problems of energy storage and greenhouse effect. However, the severe polarization of CO₂ reduction and CO₂ evolution reaction impede the practical application. Herein, anodic TiO₂ nanotube arrays are first introduced as carbon-free and free-standing cathode for photo-assisted Li–CO₂ battery, and the photo-assisted charge and discharge mechanism is first clarified from the perspective of photocatalysis. Mixed-phase TiO₂ exhibits a long cycling life of 580 h (52 cycles) at 0.025 mA cm⁻² and delivers a high discharge specific capacity of 3001 µAh cm⁻² under UV illumination. The charge voltage dramatically reduces from 4.53 to 3.03 V under UV illumination. The improvement of photo-assisted Li–CO₂ battery performance relies on the synergistic effect of the hierarchical porous structure, strong UV absorption, efficient separation, and transfer of photo-generated electrons and holes at hetero-phase junction, and the facilitation of photo-generated electrons and holes on CO₂ reduction and CO₂ evolution reaction. This work can provide useful guidance for designing efficient photocathode for photo-assisted Li–CO₂ battery and other metal–air batteries.     

Sn-Ag Synergistic Effect Enhances High-Rate Electrocatalytic CO2-to-Formate Conversion on Porous Poly(Ionic Liquid) Support

The electrocatalytic transformation of carbon dioxide (CO₂) to formate is a promising route for highly efficient conversion and utilization of CO₂ gas, due to the low production cost and the ease of storage of formate. In this work, porous poly(ionic liquid) (PPIL)-based tin-silver (Sn-Ag) bimetallic hybrids (PPIL^m-Sn_xAg_10-x) are prepared for high-performance formate electrolytic generation. Under optimal conditions, an excellent formate Faradaic efficiency of 95.5% with a high partial current density of 214.9 mA cm⁻² is obtained at −1.03 V (vs reversible hydrogen electrode). Meanwhile, the high selectivity of formate (>≈83%) is maintained in a wide potential range (>630 mV). Mechanistic studies demonstrate that the presence of Ag-species is vital for the formation, maintenance, and high dispersion of tetravalent Sn(IV)-species, which accounts for the active sites for CO₂-to-formate conversion. Further, the introduction of Ag-species significantly enhances the activity by increasing the electron density near the Fermi energy level.     

Electroreduction of Carbon Dioxide Driven by the Intrinsic Defects in the Carbon Plane of a Single Fe–N4 Site

Manipulating the in‐plane defects of metal–nitrogen–carbon catalysts to regulate the electroreduction reaction of CO₂ (CO₂RR) remains a challenging task. Here, it is demonstrated that the activity of the intrinsic carbon defects can be dramatically improved through coupling with single‐atom Fe–N₄ sites. The resulting catalyst delivers a maximum CO Faradaic efficiency of 90% and a CO partial current density of 33 mA cm^?2 in 0.1 m KHCO_3. The remarkable enhancements are maintained in concentrated electrolyte, endowing a rechargeable Zn–CO₂ battery with a high CO selectivity of 86.5% at 5 mA cm^?2. Further analysis suggests that the intrinsic defect is the active sites for CO₂RR, instead of the Fe–N₄ center. Density functional theory calculations reveal that the Fe–N₄ coupled intrinsic defect exhibits a reduced energy barrier for CO₂RR and suppresses the hydrogen evolution activity. The high intrinsic activity, coupled with fast electron‐transfer capability and abundant exposed active sites, induces excellent electrocatalytic performance.     

Synergistic Effect of N-NiMoO4/Ni Heterogeneous Interface with Oxygen Vacancies in N-NiMoO4/Ni/CNTs for Superior Overall Water Splitting

The exploring of economical, high-efficiency, and stable bifunctional catalysts for hydrogen evolution and oxygen evolution reactions (HER/OER) is highly imperative for the development of electrolytic water. Herein, a 3D cross-linked carbon nanotube supported oxygen vacancy (V_o)-rich N-NiMoO₄/Ni heterostructure bifunctional water splitting catalyst (N-NiMoO₄/Ni/CNTs) is synthesized by hydrothermal-H₂ calcination method. Physical characterization confirms that V_o-rich N-NiMoO₄/Ni nanoparticles with an average size of ≈19 nm are secondary aggregated on CNTs that form a hierarchical porous structure. The formation of Ni and NiMoO₄ heterojunctions modify the electronic structure of N-NiMoO₄/Ni/CNTs. Benefiting from these properties, N-NiMoO₄/Ni/CNTs drives an impressive HER overpotential of only 46 mV and OER overpotential of 330 mV at 10 mA cm⁻², which also shows exceptional cycling stability, respectively. Furthermore, the as-assembled N-NiMoO₄/Ni/CNTs||N-NiMoO₄/Ni/CNTs electrolyzer reaches a cell voltage of 1.64 V at 10 mA cm⁻² in alkaline solution. Operando Raman analysis reveals that surface reconstruction is essential for the improved catalytic activity. Density functional theory (DFT) calculations further demonstrate that the enhanced HER/OER performance should be attributed to the synergistic effect of V_o and heteostructure that improve the conductivity of N-NiMoO₄/Ni/CNTs and facilitatethe desorption of reaction intermediates.     

Multilayer-Cavity Tandem Catalyst for Profiling Sequentially Coupling of Intermediate CO in Electrocatalytic Reduction Reaction of CO2 to Multi-Carbon Products

Electrochemical CO₂ reduction reaction (CO₂RR) is an effective approach to address CO₂ emission, promote recycling, and synthesize high-value multi-carbon (C₂₊) chemicals for storing renewable electricity in the long-term. The construction of multilayer-bound nanoreactors to achieve management of intermediate CO is a promising strategy for tandem to C₂₊ products. In this study, a series of Ag@Cu₂O nanoreactors consisting of an Ag-yolk and a multilayer confined Cu shell is designed to profile electrocatalytic CO₂RR reactions. The optimized Ag@Cu₂O-2 nanoreactor exhibits a 74% Faradaic efficiency during the C₂₊ pathway and remains stable for over 10 h at a bias current density of 100 mA cm⁻². Using the finite element method, this model determines that the certain volume of cavity in the Ag@Cu₂O nanoreactors facilitates on-site CO retention and that multilayers of Cu species favor CO capture. Density functional theory calculations illustrate that the biased generation of ethanol products may arise from the (100)/(111) interface of the Cu layer. In-depth explorations in multilayer-bound nanoreactors provide structural and interfacial guidance for sequential coupling of CO₂RR intermediates for efficient C₂₊ generation.     

Matching CP@NCOH/NF Cathode and GH/FNP/NF Anode for High-Performance Asymmetric Supercapacitor

It is extremely crucial to design and match high-quality cathode and anode for achieving high-performance asymmetric supercapacitors (ASCs). Herein, Co₃(PO₄)₂@NiCo-LDH/Ni foam (CP@NCOH/NF) cathode with hierarchical morphology and graphene hydrogel/Fe–Ni phosphide/Ni foam (GH/FNP/NF) anode with the robust and porous structure are elaborately designed and prepared, respectively. Owing to their unique and profitable structures, both CP@NCOH/NF and GH/FNP/NF electrodes yield the superior capacity (10760 and 2236 mC cm⁻² at 2 mA cm⁻², respectively), good rate capability (63% retention at 200 mA cm⁻² and 52% retention at 50 mA cm⁻², respectively), and excellent cycling stability (72% and 74% retention after 10 000 cycles, respectively). Benefiting from their matchable electrochemical performances, the configured solid-state CP@NCOH/NF//GH/FNP/NF ASC outputs both competitive energy density (80.2 Wh kg⁻¹/4.1 mWh cm⁻³) and power density (14563 W kg⁻¹/750 mW cm⁻³), companied by remarkable cyclability (71% retention after 10 000 cycles), manifesting its great promise for large-scale integrated energy-storage system.     

Microstructure Design Strategy for Molecularly Dispersed Cobalt Phthalocyanine and Efficient Mass Transport in CO2 Electroreduction

Cobalt phthalocyanine (CoPc) has attracted particular interest owing to its excellent activity during the electrochemical CO₂ conversion to CO. However, the efficient utilization of CoPc at industrially relevant current densities is still a challenge owing to its nonconductive property, agglomeration, and unfavorable conductive substrate design. Here, a microstructure design strategy for dispersing CoPc molecules on a carbon substrate for efficient CO₂ transport during CO₂ electrolysis is proposed and demonstrated. The highly dispersed CoPc is loaded on a macroporous hollow nanocarbon sheet to act as the catalyst (CoPc/CS). The unique interconnected and macroporous structure of the carbon sheet forms a large specific surface area to anchor CoPc with high dispersion and simultaneously boosts the mass transport of reactants in the catalyst layer, significantly improving the electrochemical performance. By employing a zero-gap flow cell, the designed catalyst can mediate CO₂ to CO with a high full-cell energy efficiency of 57% at 200 mA cm⁻².