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CO2 reduction reaction (CO2RR), as a promising strategy for storing renewable energy and promoting carbon resource recycling, is critical for industrial development. Previous reports have extensively explored catalyst‐electrolyte microenvironmental modulation to elucidate coupling mechanisms and enhance catalytic conversion to multicarbon products. Currently, most reviews mainly focus on the impact of microenvironment modulation in low‐current systems on mechanism exploration and performance optimization, yet few of them can integrate macroscopic applications with microscopic investigations to explore the relevance between industrial development and catalyst‐electrolyte microenvironmental optimization. To address the gap, this review focuses on summarizing the challenges and advancements in microenvironment modulation for the development of high‐current devices. By introducing models of different scales sequentially, the connection between microenvironmental modulation and device performance is clarified. Then, various invalidation mechanisms and effective solutions are summarized to intuitively expound the impact of microenvironment modulation on high‐current stability. Meanwhile, as an intuitive measure of the rationality of microenvironment modulation, evaluation methods of device performance should be refined, which are also covered in further detail below. Finally, more valuable and challenging prospects are discussed for guiding the further industrial transformation of CO2RR. [ABSTRACT FROM AUTHOR]

Molecular modifications have shown tremendous potential in boosting the electrochemical CO2 reduction (CO2RR) to ethylene. However, the key mechanisms of modulation at the molecular level remain unclear, especially for the adsorption and activation of key intermediates (e.g., *CO2 and *CO). Here, report that a diethanolamine (DEA)‐modified Cu catalyst can reduce CO2 to ethylene with a faradaic efficiency of ≈50.5% with a partial current density of ≈155.7 mA cm−2 in the neutral conditions, which surpasses the Cu catalyst without molecular modification (≈28.5% and ≈95.6 mA cm−2). Density functional theory calculations demonstrate that DEA on the Cu surface boosts the adsorption and activation of CO2 and the following C–C coupling processes during the CO2RR‐to‐ethylene process. Molecular dynamics simulations suggest that the molecules distant from the Cu site have a CO2 enrichment effect. Operational stability achieved via the introduction of DEA molecules onto ketjen black, which then successively immobilized on the Cu nanoparticles and polytetrafluoroethylene electrodes to obtain a stable tripe‐phase boundary, realizing constant ethylene selectivity for 100 operating hours in a flow cell. [ABSTRACT FROM AUTHOR]

In response to the global climate change and energy crisis, electrocatalytic CO2 reduction reaction (ECR) is regarded as one of the potential ways to simultaneously reach the CO2 conversion and obtain various value‐added products. Currently, several challenges remain for the in‐depth understanding of ECR from fundamentals, including ambiguous structure‐activity relationships, uncontrollable catalytic selectivity, and complex reaction mechanisms. Compared to traditional metal nanoparticle‐based materials, atomically dispersed catalysts (ADCs) have aroused significant interest owing to their maximal atomic utilization and simplified site configuration, offering a superior platform for discussing the structure‐activity relationships during ECR. Especially, adjacent metal atomic pairs (AAPs) within ADCs are gradually emphasized as a novel concept to follow various synergistic reaction mechanisms during ECR. Herein, for the first time a broad concept of AAPs and analyzed how AAPs within ADCs reached the synergistic effect during ECR is summarized. In view of the synergistic reaction mechanisms varying on different supports, three types of supports are illustrated (containing graphene model, functional porous frameworks, and metals and oxides), aiming to help scholars with more insights in broadening the feasible synergistic reaction mechanisms on AAPs within ADCs. [ABSTRACT FROM AUTHOR]

Electrocatalytic CO2 to multi‐carbon products is an attractive strategy to achieve a carbon‐neutral energy cycle. Single‐atom catalysts (SACs) that achieve the C2 selectivity always have low metal loading and inevitably undergo in situ reversible/irreversible metallic agglomerations under working conditions. Herein, a high‐density Cu SA anchored F, O, N co‐doped carbon composites (CuFONC) with a stable CuN2O1 configuration is provided, which can reach a remarkable C2 selectivity of ≈80.5% in Faradaic efficiency at −1.3 V versus RHE. In situ/ex situ experimental characterization and density functional theory (DFT) calculations verified that the excellent stability of CuN2O1 during the CO2RR process can be attributed to F/O co‐derived regulation for CuFONC. Remarkably, as confirmed by DFT, it is atomic Cu sites and the adjacent bonded N motifs in CuFONC that act as the adsorption sites for CO* during the C─C coupling process. This work brings a prospective on designing novel but stable atomic Cu coordination for electrolytic CO2‐to‐C2 pathway. [ABSTRACT FROM AUTHOR]

Single atomic catalysts (SACs) offer a superior platform for studying the structure–activity relationships during electrocatalytic CO2 reduction reaction (CO2RR). Yet challenges still exist to obtain well‐defined and novel site configuration owing to the uncertainty of functional framework‐derived SACs through calcination. Herein, a novel Bi−N2O2 site supported on the (1 1 0) plane of hydrogen‐bonded organic framework (HOF) is reported directly for CO2RR. In flow cell, the target catalyst Bi1‐HOF maintains a faradaic efficiency (FE) HCOOH of over 90 % at a wide potential window of 1.4 V. The corresponding partial current density ranges from 113.3 to 747.0 mA cm−2. And, Bi1‐HOF exhibits a long‐term stability of over 30 h under a successive potential‐step test with a current density of 100–400 mA cm−2. Density function theory (DFT) calculations illustrate that the novel Bi−N2O2 site supported on the (1 1 0) plane of HOF effectively induces the oriented electron transfer from Bi center to CO2 molecule, reaching an enhanced CO2 activation and reduction. Besides, this study offers a versatile method to reach series of M−N2O2 sites with regulable metal centers via the same intercalation mechanism, broadening the platform for studying the structure–activity relationships during CO2RR. [ABSTRACT FROM AUTHOR]

The electrochemical CO2 (eCO2)‐to‐multicarbon conversion with higher value is regarded as a potential way to promote the transformation of industrial production and the green balance of carbon cycle. Recently, a series of advances have been achieved in the progress of eCO2‐to‐multicarbon conversion, including the in‐depth exploration of coupling mechanisms, the up‐to‐date development of characterization techniques, and the novel interdisciplinary design strategies of catalysts and electrolytic systems. Therefore, it is essential to systematically overview the eCO2‐to‐multicarbon conversion from fundamentals to industrialization, compensating for the limited and insufficient reviews that have been reported. To fill the aforementioned research gap, this overview is focused on the eCO2‐to‐multicarbon conversion from fundamentals to industrialization. First, the possible catalytic mechanisms for eCO2‐to‐multicarbon conversion are accordingly summarized in the order of eCO2 reduction, small molecule‐coupled eCO2 reduction, and eCO2 tandem conversion. Second, the up‐to‐date in situ characterization technologies assisting the rationalization of coupling mechanisms are presented. Third, the optimizing strategies of catalysts and electrolytic systems are briefly classified for the advance of industrialization process. Finally, challenges and perspectives for the further development of eCO2‐to‐multicarbon conversion are reasonably proposed, aiming to offer insights for the following work in this field. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) have been regarded as an effective means to transform hydrogen energy into electric energy, which is featured with high energy density, excellent conversion efficiency, and environmental friendliness. Carbon nanomaterials are the most widely used supports for the state-of-the-art Pt-based PEMFC cathode catalysts. Nonetheless, the corrosion of carbon supports under high potential environment would inevitably lead to the dissolution/ripening of Pt, resulting in the severe degradation of their PEMFC performance. Carbon-free materials, such as transition metal oxides/nitrides/sulfides/carbides (TMOs, TMNs, TMSs, and TMCs), can effectively prevent this issue with their excellent intrinsic stability and tuned metal–support interactions (MSI). Recently, numerous researches have been focused on the design and preparation of carbon-free PEMFC cathode catalysts. Meanwhile, MSI effect, including d-band center, migration energy barrier, defect sites, coordination environment, and electron transfer ability, have also been considered to improve the PEMFCs performance. In this review, the MSI effect of carbon-free PEMFC cathode materials and their common adjustment strategies are systematically summarized. Then, details about the pristine and modified carbon-free PEMFC catalysts and their specific structure–activity relationships induced by MSI effect are further illustrated in the order of TMOs, TMCs, TMNs, and TMSs. Finally, the challenges and perspectives of carbon-free PEMFC cathode catalysts are further proposed to provide insights into future researches in this PEMFC field. [ABSTRACT FROM AUTHOR]

Developing highly efficient and stable hydrogen production catalysts for electrochemical water splitting (EWS) at industrial current densities remains a great challenge. Herein, we proposed a heterostructure‐induced‐strategy to optimize the metal‐support interaction (MSI) and the EWS activity of Ru‐Ni3N/NiO. Density functional theory (DFT) calculations firstly predicted that the Ni3N/NiO‐heterostructures can improve the structural stability, electronic distributions, and orbital coupling of Ru‐Ni3N/NiO compared to Ru‐Ni3N and Ru‐NiO, which accordingly decreases energy barriers and increases the electroactivity for EWS. As a proof‐of‐concept, the Ru‐Ni3N/NiO catalyst with a 2D Ni3N/NiO‐heterostructures nanosheet array, uniformly dispersed Ru nanoparticles, and strong MSI, was successfully constructed in the experiment, which exhibited excellent HER and OER activity with overpotentials of 190 mV and 385 mV at 1000 mA cm−2, respectively. Furthermore, the Ru‐Ni3N/NiO‐based EWS device can realize an industrial current density (1000 mA cm−2) at 1.74 V and 1.80 V under alkaline pure water and seawater conditions, respectively. Additionally, it also achieves a high durability of 1000 h (@ 500 mA cm−2) in alkaline pure water. [ABSTRACT FROM AUTHOR]

The electrocatalytic CO2 reduction reaction (ECO2RR) is considered one of the approaches with the most potential to achieve lower carbon emissions in the future, but a huge gap still exists between the current ECO2RR technology and industrial applications. Therefore, the design and preparation of catalysts with satisfactory activity, selectivity and stability for the ECO2RR have attracted extensive attention. As a classic type of functional porous framework, crystalline porous materials (e.g., metal organic frameworks (MOFs) and covalent organic frameworks (COFs)) and derived porous materials (e.g., MOF/COF composites and pyrolysates) have been regarded as superior catalysts for the ECO2RR due to their advantages such as designable porosity, modifiable skeleton, flexible active site structure, regulable charge transfer pathway and controllable morphology. Meanwhile, with the rapid development of nano-characterization and theoretical calculation technologies, the structure–activity relationships of functional porous frameworks have been comprehensively considered, i.e., metallic element type, local coordination environment, and microstructure, corresponding to selectivity, activity and mass transfer efficiency for the ECO2RR, respectively. In this review, the rational design strategy for functional porous frameworks is briefly but precisely generalized based on three key factors including metallic element type, local coordination environment, and microstructure. Then, details about the structure–activity relationships for functional porous frameworks are illustrated in the order of MOFs, COFs, composites and pyrolysates to analyze the effect of the above-mentioned three factors on their ECO2RR performance. Finally, the challenges and perspectives of functional porous frameworks for the further development of the ECO2RR are reasonably proposed, aiming to offer insights for future studies in this intriguing and significant research field. [ABSTRACT FROM AUTHOR]

It is very important to design and prepare low-cost and high-efficiency electrocatalysts for water splitting in alkaline solution. In this study, Ni–Fe–P and Ni–Fe–P–FeMnO3 electrocatalysts are developed using a facile electrodeposition method. Transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) characterization studies show that FeMnO3 particles are successfully composited into the Ni–Fe–P amorphous matrix, and multi-stage nanostructures are obtained which enable the exposure of more active sites for the hydrogen evolution reaction. The Ni–Fe–P electrocatalyst prepared at a deposition current density of 150 mA cm−2 exhibits remarkable hydrogen evolution reaction catalytic activity, and only requires 39.7 mV overpotential at 10 mA cm−2 current density. Compared with the Ni–Fe–P electrode, the Ni–Fe–P–FeMnO3 electrode shows more outstanding electrocatalytic properties requiring only 13.5 mV overpotential at 10 mA cm−2 current density. The fabricated Ni–Fe–P–FeMnO3 electrode is able to sustain a current density of 10 mA cm−2 with negligible increase in overpotential in 24 h which shows remarkable electrochemical stability. [ABSTRACT FROM AUTHOR]

2D functional porous frameworks offer a platform for studying the structure-activity relationships during electrocatalytic CO2 reduction reaction (CO2RR). Yet challenges still exist to breakthrough key limitations on site configuration (typical M-O4 or M-N4 units) and product selectivity (common CO2-to-CO conversion). Herein, a novel 2D metal-organic framework (MOF) with planar asymmetric N/O mixed coordinated Cu-N1O3 unit is constructed, labeled as BIT-119. When applied to CO2RR, BIT-119 could reach a CO2-to-C2 conversion with C2 partial current density ranging from 36.9 to 165.0 mA cm-2 in flow cell. Compared to the typical symmetric Cu-O4 units, asymmetric Cu-N1O3 units lead to the re-distribution of local electron structure, regulating the adsorption strength of several key adsorbates and the following catalytic selectivity. From experimental and theoretical analyses, Cu-N1O3 sites could simultaneously couple the atop-type (on Cu site) and bridge-type (on Cu-N site) adsorption of *C1 species to reach the CO2-to-C2 conversion. This work broadens the feasible C-C coupling mechanism on 2D functional porous frameworks., (© 2024 Wiley‐VCH GmbH.)

Single atomic catalysts (SACs) offer a superior platform for studying the structure-activity relationships during electrocatalytic CO 2 reduction reaction (CO 2 RR). Yet challenges still exist to obtain well-defined and novel site configuration owing to the uncertainty of functional framework-derived SACs through calcination. Herein, a novel Bi-N 2 O 2 site supported on the (1 1 0) plane of hydrogen-bonded organic framework (HOF) is reported directly for CO 2 RR. In flow cell, the target catalyst Bi1-HOF maintains a faradaic efficiency (FE) HCOOH of over 90 % at a wide potential window of 1.4 V. The corresponding partial current density ranges from 113.3 to 747.0 mA cm -2 . And, Bi1-HOF exhibits a long-term stability of over 30 h under a successive potential-step test with a current density of 100-400 mA cm -2 . Density function theory (DFT) calculations illustrate that the novel Bi-N 2 O 2 site supported on the (1 1 0) plane of HOF effectively induces the oriented electron transfer from Bi center to CO 2 molecule, reaching an enhanced CO 2 activation and reduction. Besides, this study offers a versatile method to reach series of M-N 2 O 2 sites with regulable metal centers via the same intercalation mechanism, broadening the platform for studying the structure-activity relationships during CO 2 RR., (© 2024 Wiley-VCH GmbH.)

Developing highly efficient and stable hydrogen production catalysts for electrochemical water splitting (EWS) at industrial current densities remains a great challenge. Herein, we proposed a heterostructure-induced-strategy to optimize the metal-support interaction (MSI) and the EWS activity of Ru-Ni 3 N/NiO. Density functional theory (DFT) calculations firstly predicted that the Ni 3 N/NiO-heterostructures can improve the structural stability, electronic distributions, and orbital coupling of Ru-Ni 3 N/NiO compared to Ru-Ni 3 N and Ru-NiO, which accordingly decreases energy barriers and increases the electroactivity for EWS. As a proof-of-concept, the Ru-Ni 3 N/NiO catalyst with a 2D Ni 3 N/NiO-heterostructures nanosheet array, uniformly dispersed Ru nanoparticles, and strong MSI, was successfully constructed in the experiment, which exhibited excellent HER and OER activity with overpotentials of 190 mV and 385 mV at 1000 mA cm -2 , respectively. Furthermore, the Ru-Ni 3 N/NiO-based EWS device can realize an industrial current density (1000 mA cm -2 ) at 1.74 V and 1.80 V under alkaline pure water and seawater conditions, respectively. Additionally, it also achieves a high durability of 1000 h (@ 500 mA cm -2 ) in alkaline pure water., (© 2023 Wiley-VCH GmbH.)

The electrocatalytic CO 2 reduction reaction (ECO 2 RR) is considered one of the approaches with the most potential to achieve lower carbon emissions in the future, but a huge gap still exists between the current ECO 2 RR technology and industrial applications. Therefore, the design and preparation of catalysts with satisfactory activity, selectivity and stability for the ECO 2 RR have attracted extensive attention. As a classic type of functional porous framework, crystalline porous materials ( e.g. , metal organic frameworks (MOFs) and covalent organic frameworks (COFs)) and derived porous materials ( e.g. , MOF/COF composites and pyrolysates) have been regarded as superior catalysts for the ECO 2 RR due to their advantages such as designable porosity, modifiable skeleton, flexible active site structure, regulable charge transfer pathway and controllable morphology. Meanwhile, with the rapid development of nano-characterization and theoretical calculation technologies, the structure-activity relationships of functional porous frameworks have been comprehensively considered, i.e. , metallic element type, local coordination environment, and microstructure, corresponding to selectivity, activity and mass transfer efficiency for the ECO 2 RR, respectively. In this review, the rational design strategy for functional porous frameworks is briefly but precisely generalized based on three key factors including metallic element type, local coordination environment, and microstructure. Then, details about the structure-activity relationships for functional porous frameworks are illustrated in the order of MOFs, COFs, composites and pyrolysates to analyze the effect of the above-mentioned three factors on their ECO 2 RR performance. Finally, the challenges and perspectives of functional porous frameworks for the further development of the ECO 2 RR are reasonably proposed, aiming to offer insights for future studies in this intriguing and significant research field.

Exploring functional substrates and precisely regulating the electronic structures of atomic metal active species with moderate spin state are of great importance yet remain challenging. Hereon, we provide an axial Fe-O-Ti ligand regulated spin-state transition strategy to improve the oxygen reduction reaction (ORR) activity of Fe centers. Theoretical calculations indicate that Fe-O-Ti ligands in FeN 3 O-O-Ti can induce a low-to-medium spin-state transition and optimize O 2 adsorption by FeN 3 O. As a proof-of-concept, the oriented catalyst was prepared from atomic-Fe-doped polymer-like quantum dots and ultrathin o-terminated MXene. The optimal catalyst exhibits an intrinsic activity that is almost 5 times higher than the control sample (without axial Fe-O-Ti ligands). It also delivers a superior performance in Zn-air batteries and H 2 /O 2 anion exchange membrane fuel cells in a wide-temperature range., (© 2022 Wiley-VCH GmbH.)