Bi2O3/BiO2 Nanoheterojunction for Highly Efficient Electrocatalytic CO2 Reduction to Formate

Ultrasound-activated sonothermal-catalytic synergistic therapy via asymmetric electron distribution for bacterial wound infections

Antibiotic-resistant bacterial infections present a growing global health challenge, requiring innovative therapeutic solutions to overcome current limitations. We introduce boron-integrated bismuth oxide (B-BiO2) nanosheets with an asymmetrically distributed electronic structure for ultrasound-activated synergistic sonothermal and catalytic therapy. Boron incorporation enhances local electron density distribution, optimizing charge separation and significantly improving sonothermal and catalytic efficiency, as validated by density functional theory calculations. These nanosheets exhibit dual functionality, effectively generating localized heat and reactive oxygen species (ROS) under ultrasound, leading to 99.999 % antibacterial efficacy against multidrug-resistant pathogens by disrupting bacterial membranes, as demonstrated through all-atom simulations and in vitro experiments. The simulations further reveal that sonothermal conversion effects enhance bacterial membrane fluidity and induce structural defects, amplifying ROS-induced oxidative damage and membrane destabilization. In vivo, B-BiO2 nanosheets accelerate wound healing in methicillin-resistant Staphylococcus aureus (MRSA)-infected murine models, achieving 99.8 % closure by day 14 by reducing inflammation and promoting angiogenesis and tissue regeneration. Transcriptomic analysis highlights the activation of extracellular matrix remodeling, angiogenesis, and autophagy pathways, underscoring the nanosheets' therapeutic potential. This study establishes ultrasound-activated B-BiO2 nanosheets as a novel nanotherapeutic platform, leveraging asymmetric electron distribution to synergistically combat drug-resistant infections and promote effective wound healing.

Electronic Modulation of Bismuth by g-C3N4 Constructs Electron-Enriched Active Sites for Accelerated CO2 Electroreduction to Formate

Electrochemical reduction of CO2 (ECO2RR) to formate represents a promising approach to achieving carbon neutrality, yet it faces significant challenges due to the low adsorption efficiency of the CO2 intermediates. In this study, we developed a highly dispersed electron-rich Bi metal catalyst, utilizing low-cost g-C3N4 as a nonmetallic support and electron donor. This design created a conductive network and a multielectron environment around the Bi atoms that facilitated dynamic interfacial charge transfer from g-C3N4 to Bi, thus enhancing the catalytic efficiency of active sites. The assembly catalyst exhibited a formate selectivity of over 90% within a wide potential window and maintained stable catalytic activity in simulated seawater solutions. In situ Raman spectroscopy and DFT calculations indicated that the incorporation of the nonmetallic support shifted the Bi-p band center to more negative values while increasing Bader charge transfer between Bi and *OCHO intermediates. This indicated enhanced adsorption of the *OCHO intermediate by electron-rich Bi, thus improving the selectivity and activity for formate production.

Engineering p-d Orbital Coupling and Vacancy-Rich Structure in Triatomic Iron-Bismuth-Iron Sites for Rechargeable Zinc-Air Batteries

The rational design of heteroatomic sites with synergistic electronic modulation remains a critical challenge for achieving bifunctional oxygen electrocatalysis in sustainable energy technologies such as fuel cells and metal-air batteries. Herein, a triatomic Fe2BiN5 configuration embedded in nitrogen-doped carbon (Fe2BiN5/C) with atomically dispersed FeN2-BiN-FeN2 sites and vacancy-rich structures is synthesized via a pyrolysis and etching strategy. The triatomic architecture endows Fe2BiN5/C with exceptional bifunctional activity, delivering a high oxygen reduction reaction half-wave potential of 0.918 V and an oxygen evolution reaction overpotential of 245 mV at 10 mA cm-2, surpassing Pt/C and RuO2. In situ X-ray absorption fine structure and Raman spectroscopy reveal dynamic structural evolution during electrocatalysis, where Fe acts as the primary active center with Bi regulating the electron distribution via long-range interactions, thereby optimizing adsorption/desorption energetics of oxygen intermediates. The theoretical calculations further elucidate that the Bi-induced p-d orbital coupling leads to the alteration in Fe d-orbitals energy level, downshift d-band center, weaken binding strength to the oxygen-based intermediates, and reduced energy barrier for oxygen electrocatalysis. This work provides an understanding of bifunctional triatomic site with p-block metal as electronic modulators embedded in transition-metal atoms toward enhanced oxygen catalysis.

Stabilizing Lattice Oxygen of Bi2O3 by Interstitial Insertion of Indium for Efficient Formic Acid Electrosynthesis

Bismuth oxide (Bi2O3) emerges as a potent catalyst for converting CO2 to formic acid (HCOOH), leveraging its abundant lattice oxygen and the high activity of its Bi-O bonds. Yet, its durability is usually impeded by the loss of lattice oxygen causing structure alteration and destabilized active bonds. Herein, we report an innovative approach via the interstitial incorporation of indium (In) into the Bi2O3, significantly enhancing bond stability and preserving lattice oxygen. The optimized In-Bi2O3-100 catalyst achieves over 90 % Faradaic efficiency for HCOOH production across a wide potential range, in both H-cells and flow cells, maintaining robust stability after 100 hours of continuous operation. In situ surface-enhanced infrared absorption spectroscopy and theoretical calculations reveal that the interstitial In doping precisely tunes the adsorption of CO2* and OCHO* intermediate, facilitating rapid conversion. Further in situ Raman spectroscopy confirms the role of In bolstering the oxidized structure's stability within Bi2O3, critical for sustaining lattice oxygen during electrochemical CO2 reduction.

In2O3/Bi2O3 interface induces ultra-stable carbon dioxide electroreduction on heterogeneous InBiOx catalyst

The electrochemical reduction of CO2 (ERCO2) has emerged as one of the most promising methods for achieving both renewable energy storage and CO2 recovery. However, achieving both high selectivity and stability of catalysts remains a significant challenge. To address this challenge, this study investigated the selective synthesis of formate via ERCO2 at the interface of In2O3 and Bi2O3 in the InBiO6 composite material. Moreover, InBiO6 was synthesized using indium-based metal-organic frameworks as precursor, which underwent continuous processing through ion exchange and thermal reduction. The results revealed that the formate Faradaic efficiency (FEformate) of InBiO6 reached nearly 100 % at -0.86 V vs. reversible hydrogen electrode (RHE) and remained above 90 % after continuous 317-h electrolysis, which exceeded those of previously reported indium-based catalysts. Additionally, the InBiO6 composite material exhibited an FEformate exceeding 80 % across a wide potential range of 500 mV from -0.76 to -1.26 V vs. RHE. Density-functional theory analysis confirmed that the heterogeneous interface of InBiO6 played a role in achieving optimal free energies for *OCHO on its surface. Furthermore, the addition of Bi to the InBiO6 matrix facilitated electron transfer and altered the electronic structure of In2O3, thereby enhancing the adsorption, decomposition, and formate production of *OCHO.

Modulation of charge structure in Bi/Bi2O3-In2O3@C for efficient CO2 electroreduction to formate

Electrocatalytic CO2 reduction reaction (ECO2RR) to value-added chemicals is of significant importance to control CO2 emission and reach carbon neutrality. Herein, Bi/Bi2O3-In2O3@C electrocatalyst with nanosheet arrays is successfully fabricated by a facile solvothermal with subsequent calcination process. It is found that the electron structure of Bi/Bi2O3-In2O3@C can be adjusted by the synergistic effects of Bi-In hetero-diatoms, which can significantly enhance its inherent catalytic activity. As expected, it requires a maximum HCOOH faradaic efficiency (FEHCOOH) of 97.6 % at -1.1 V vs. Reversible Hydrogen Electrode (RHE), which further delivers over 90 % at a wide potential range of -0.8 to -1.4 V vs. RHE, and exhibits high stability of 90.1 % over 60-h long-term test. In-situ Raman analysis is performed to explore the mechanism of its excellent stability. Meanwhile, in-situ attenuated total reflection-Fourier-transform infrared (ATR-FTIR) analysis combined with theoretical calculations reveal that the hetero-bridging absorption of *OCHO and d-d orbital coupling effect can regulate d-band center of Bi/Bi2O3-In2O3@C and improve its density of states around Ef, moderating free energy of intermediates, thereby the improved formate production performance can be seen.

Fundamentals and Challenges of Ligand Modification in Heterogeneous Electrocatalysis

The development of efficient catalytic materials in the energy field could promote the structural transformation from traditional fossil fuels to sustainable energy. In heterogeneous catalytic reactions, ligand modification is an effective way to regulate both electronic and steric structures of catalytic sites, thus paving a prospective avenue to design the interfacial structures of heterogeneous catalysts for energy conversion. Although great achievements have been obtained for the study and applications of heterogeneous ligand-modified catalysts, the systematical refinements of ligand modification strategies are still lacking. Here, we reviewed the ligand modification strategy from both the mechanistic and applicable scenarios by focusing on heterogeneous electrocatalysis. We elucidated the ligand-modified catalysts in detail from the perspectives of basic concepts, preparation, regulation of physicochemical properties of catalytic sites, and applications in different electrocatalysis. Notably, we bridged the electrocatalytic performance with the electronic/steric effects induced by ligand modification to gain intrinsic structure-performance relations. We also discussed the challenges and future perspectives of ligand modification strategies in heterogeneous catalysis.

Copper as an Electron Hunter for Enhancing Bi2O2CO3 Electrocatalytic CO2 Conversion to Formate

Cu-doped Bi2O2CO3 catalyst with copper (Cu) acting an electron hunter for conversion of carbon dioxide into formate is developed. The Cu-Bi2O2CO3 catalyst with hollow microsphere structure extends the duration of CO2 retention on the catalyst, providing a greater number of active sites. It exhibits remarkable performance with conversion efficacy of 98.5% and current density of 800 mA cm-2 across a wide potential window (-0.8 to -1.3 V vs RHE). Density functional theory investigations reveal that the presence of copper (Cu) significantly enhances the charge density at the active sites and influences the local electronic structure of bismuth (Bi), thereby reducing the energy barrier associated with the transformation of *OCHO species into formate.

Rational Strategies for Preparing Highly Efficient Tin-, Bismuth- or Indium-Based Electrocatalysts for Electrochemical CO2 Reduction to Formic acid/Formate

Electrochemical carbon dioxide reduction reaction (CO2RR) is an environmentally friendly and economically viable approach to convert greenhouse gas CO2 into valuable chemical fuels and feedstocks. Among various products of CO2RR, formic acid/formate (HCOOH/HCOO-) is considered the most attractive one with its high energy density and ease of storage, thereby enabling widespread commercial applications in chemical, medicine, and energy-related industries. Nowadays, the development of efficient and financially feasible electrocatalysts with excellent selectivity and activity towards HCOOH/HCOO- is paramount for the industrial application of CO2RR technology, in which Tin (Sn), Bismuth (Bi), and Indium (In)-based electrocatalysts have drawn significant attention due to their high efficiency and various regulation strategies have been explored to design diverse advanced electrocatalysts. Herein, we comprehensively review the rational strategies to enhance electrocatalytic performances of these electrocatalysts for CO2RR to HCOOH/HCOO-. Specifically, the internal mechanism between the physicochemical properties of engineering materials and electrocatalytic performance is analyzed and discussed in details. Besides, the current challenges and future opportunities are proposed to provide inspiration for the development of more efficient electrocatalysts in this field.

Microfluidic Continuous Synthesis of Size- and Facet-Controlled Porous Bi2O3 Nanospheres for Efficient CO2 to Formate Catalysis

Bismuth-based catalysts are effective in converting carbon dioxide into formate via electrocatalysis. Precise control of the morphology, size, and facets of bismuth-based catalysts is crucial for achieving high selectivity and activity. In this work, an efficient, large-scale continuous production strategy is developed for achieving a porous nanospheres Bi2O3-FDCA material. First-principles simulations conducted in advance indicate that the Bi2O3 (111)/(200) facets help reduce the overpotential for formate production in electrocatalytic carbon dioxide reduction reaction (ECO2RR). Subsequently, using microfluidic technology and molecular control to precisely adjust the amount of 2, 5-furandicarboxylic acid, nanomaterials rich in (111)/(200) facets are successfully synthesized. Additionally, the morphology of the porous nanospheres significantly increases the adsorption capacity and active sites for carbon dioxide. These synergistic effects allow the porous Bi2O3-FDCA nanospheres to stably operate for 90 h in a flow cell at a current density of ≈250 mA cm- 2, with an average Faradaic efficiency for formate exceeding 90%. The approach of theoretically guided microfluidic technology for the large-scale synthesis of finely structured, efficient bismuth-based materials for ECO2RR may provide valuable references for the chemical engineering of intelligent nanocatalysts.

Interfacial Electronic Interaction in Amorphous-Crystalline CeOx-Sn Heterostructures for Optimizing CO2 to Formate Conversion

Formate, a crucial chemical raw material, holds significant promise for industrial applications in the context of CO2 electroreduction reaction (CO2RR). Despite its potential, challenges, such as poor selectivity and low formation rate at high current densities persist, primarily due to the competing hydrogen evolution reaction (HER) and high energy barriers associated with *OCHO intermediate generation. Herein, one-step chemical co-reduction strategy is employed to construct an amorphous-crystalline CeOx-Sn heterostructure, demonstrating remarkable catalytic performance in converting CO2 to formate. The optimized CeOx-Sn heterostructures reach a current density of 265.1 mA cm-2 and a formate Faraday efficiency of 95% at -1.07 V versus RHE. Especially, CeOx-Sn achieves a formate current density of 444.4 mA cm-2 and a formate production rate of 9211.8 µmol h-1 cm-2 at -1.67 V versus RHE, surpassing most previously reported materials. Experimental results, coupled with （density functional theory）DFT calculations confirm that robust interface interaction between CeOx and Sn active center induces electron transfer from crystalline Sn site to amorphous CeOx, some Ce4+of CeOx get electrons and convert to unsaturated Ce3+, optimizing the electronic structure of active Sn. This amorphous-crystalline heterostructure promotes electron transfer during CO2RR, reducing the energy barrier formed by *OCHO intermediates, and thus achieving efficient reduction of CO2 to formate.

Recent advances in dynamic reconstruction of electrocatalysts for carbon dioxide reduction

Electrocatalysts undergo structural evolution under operating electrochemical CO2 reduction reaction (CO2RR) conditions. This dynamic reconstruction correlates with variations in CO2RR activity, selectivity, and stability, posing challenges in catalyst design for electrochemical CO2RR. Despite increased research on the reconstruction behavior of CO2RR electrocatalysts, a comprehensive understanding of their dynamic structural evolution under reaction conditions is lacking. This review summarizes recent developments in the dynamic reconstruction of catalysts during the CO2RR process, covering fundamental principles, modulation strategies, and in situ/operando characterizations. It aims to enhance understanding of electrocatalyst dynamic reconstruction, offering guidelines for the rational design of CO2RR electrocatalysts.

In Situ Reconstruction of Scalable Amorphous Indium-Based Metal-Organic Framework for CO2 Electroreduction to Formate over an Ultrawide Potential Window

Amorphous metal-organic frameworks (aMOFs) are highly attractive for electrocatalytic applications due to their exceptional conductivity and abundant defect sites, but harsh preparation conditions of "top-down" strategy have hindered their widespread use. Herein, the scalable production of aMIL-68(In)-NH2 was successfully achieved through a facile "bottom-up" strategy involving ligand competition with 2-methylimidazole. Multiple in situ and ex situ characterizations reveal that aMIL-68(In)-NH2 evolutes into In/In2O3-x as the genuine active sites during the CO2 electrocatalytic reduction (CO2RR) process. Moreover, the retained amino groups could enhance the CO2 adsorption. As expected, the reconstructed catalyst demonstrates high formate Faradaic efficiency values (>90%) over a wide potential range of 800 mV in a flow cell, surpassing most top-ranking electrocatalysts. Density functional theory calculations reveal that the abundant oxygen vacancies in aMIL-68(In)-NH2 induce more local charges around electroactive sites, thereby promoting the formation of HCOO* intermediates. Furthermore, 16 g of samples can be readily prepared in one batch and exhibit almost identical CO2RR performances. This work offers a feasible batch-scale strategy to design amorphous MOFs for the highly efficient electrolytic CO2RR.

Theoretical Prediction Leads to Synthesize GDY Supported InOx Quantum Dots for CO2 Reduction

The preparation of formic acid by direct reduction of carbon dioxide is an important basis for the future chemical industry and is of great significance. Due to the serious shortage of highly active and selective electrocatalysts leading to the development of direct reduction of carbon dioxide is limited. Herein the target catalysts with high CO2RR activity and selectivity were identified by integrating DFT calculations and high-throughput screening and by using graphdiyne (GDY) supported metal oxides quantum dots (QDs) as the ideal model. It is theoretically predicted that GDY supported indium oxide QDs (i.e., InOx/GDY) is a new heterostructure electrocatalyst candidate with optimal CO2RR performance. The interfacial electronic strong interactions effectively regulate the surface charge distribution of QDs and affect the adsorption/desorption behavior of HCOO* intermediate during CO2RR to achieve highly efficient CO2 conversion. Based on the predicted composition and structure, we synthesized the advanced catalytic system, and demonstrates superior CO2-to-HCOOH conversion performance. The study presents an effective strategy for rational design of highly efficient heterostructure electrocatalysts to promote green chemical production.

Local CO2 reservoir layer promotes rapid and selective electrochemical CO2 reduction

Electrochemical CO2 reduction reaction in aqueous electrolytes is a promising route to produce added-value chemicals and decrease carbon emissions. However, even in Gas-Diffusion Electrode devices, low aqueous CO2 solubility limits catalysis rate and selectivity. Here, we demonstrate that when assembled over a heterogeneous electrocatalyst, a film of nitrile-modified Metal-Organic Framework (MOF) acts as a remarkable CO2-solvation layer that increases its local concentration by ~27-fold compared to bulk electrolyte, reaching 0.82 M. When mounted on a Bi catalyst in a Gas Diffusion Electrode, the MOF drastically improves CO2-to-HCOOH conversion, reaching above 90% selectivity and partial HCOOH currents of 166 mA/cm2 (at -0.9 V vs RHE). The MOF also facilitates catalysis through stabilization of reaction intermediates, as identified by operando infrared spectroscopy and Density Functional Theory. Hence, the presented strategy provides new molecular means to enhance heterogeneous electrochemical CO2 reduction reaction, leading it closer to the requirements for practical implementation.

Unveiling pH-Dependent Adsorption Strength of *CO2 - Intermediate over High-Density Sn Single Atom Catalyst for Acidic CO2-to-HCOOH Electroreduction

The acidic electrochemical CO2 reduction reaction (CO2RR) for direct formic acid (HCOOH) production holds promise in meeting the carbon-neutral target, yet its performance is hindered by the competing hydrogen evolution reaction (HER). Understanding the adsorption strength of the key intermediates in acidic electrolyte is indispensable to favor CO2RR over HER. In this work, high-density Sn single atom catalysts (SACs) were prepared and used as catalyst, to reveal the pH-dependent adsorption strength and coverage of *CO2 - intermediatethat enables enhanced acidic CO2RR towards direct HCOOH production. At pH=3, Sn SACs could deliver a high Faradaic efficiency (90.8 %) of HCOOH formation and a corresponding partial current density up to -178.5 mA cm-2. The detailed in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic studies reveal that a favorable alkaline microenvironment for CO2RR to HCOOH is formed near the surface of Sn SACs, even in the acidic electrolyte. More importantly, the pH-dependent adsorption strength of *CO2 - intermediate is unravelled over the Sn SACs, which in turn affects the competition between HER and CO2RR in acidic electrolyte.

Revealing the Intrinsic Restructuring of Bi2O3 Nanoparticles into Bi Nanosheets during Electrochemical CO2 Reduction

Bismuth is a catalyst material that selectively produces formate during the electrochemical reduction of CO2. While different synthesis strategies have been employed to create electrocatalysts with better performance, the restructuring of bismuth precatalysts during the reaction has also been previously reported. The mechanism behind the change has, however, remained unclear. Here, we show that Bi2O3 nanoparticles supported on Vulcan carbon intrinsically transform into stellated nanosheet aggregates upon exposure to an electrolyte. Liquid cell transmission electron microscopy observations first revealed the gradual restructuring of the nanoparticles into nanosheets in the presence of 0.1 M KHCO3 without an applied potential. Our experiments also associated the restructuring with solubility of bismuth in the electrolyte. While the consequent agglomerates were stable under moderate negative potentials (-0.3 VRHE), they dissolved over time at larger negative potentials (-0.4 and -0.5 VRHE). Operando Raman spectra collected during the reaction showed that under an applied potential, the oxide particles reduced to metallic bismuth, thereby confirming the metal as the working phase for producing formate. These results inform us about the working morphology of these electrocatalysts and their formation and degradation mechanisms.

Two-way rushing travel: Cathodic-anodic coupling of Bi2O3-SnO@CuO nanowires, a bifunctional catalyst with excellent CO2RR and MOR performance for the efficient production of formate

Electrocatalytic carbon dioxide reduction reaction (CO2RR) generates high value-added products and simultaneously reduces excess atmospheric CO2 concentrations, is regarded as a potential approach to achieve carbon neutrality. However, the kinetic process of the anode oxygen evolution reaction (OER) is slow, resulting in a poor electrochemical efficiency of CO2RR. It is a breakthrough to replace OER with methanol oxidation reaction (MOR), which has more advantageous reaction kinetics. Herein, this work proposed a bifunctional catalyst Bi2O3-SnO modified CuO nanowires (Bi2O3-SnO@CuO NWs) with excellent CO2RR and MOR performance. For CO2RR, Bi2O3-SnO@CuO NWs achieved more than 90% formate selectivity at wide potential windows from -0.88 to -1.08 V (vs. reversible hydrogen electrode (RHE)), peaking at 96.6%. Meanwhile, anodic Bi2O3-SnO@CuO NWs achieved 100 mA cm-2 at a low potential of 1.53 V (vs. RHE), possessing nearly 100% formate selectivity ranging from 1.6 to 1.8 V (vs. RHE). Impressively, by coupling cathodic CO2RR and anodic MOR, the integrated electrolytic cell realized co-production of formate (cathode: 94.7% and anode: 97.5%), minimizing the energy input by approximately 69%, compared with CO2RR. This work provided a meaningful perspective for the design of bifunctional catalysts and coupling reaction systems in CO2RR.

Deep Electronic State Regulation through Unidirectional Cascade Electron Transfer Induced by Dual Junction Boosting Electrocatalysis Performance

Unidirectional cascade electron transfer induced by multi-junctions is essential for deep electronic state regulation of the catalytic active sites, while this advanced concept has rarely been investigated in the field of electrocatalysis. In the present work, a dual junction heterostructure (FePc/L-R/CN) is designed by anchoring iron phthalocyanine (FePc)/MXene (L-Ti3 C2 -R, R═OH or F) heterojunction on g-C3 N4 nanosheet substrates for electrocatalysis. The unidirectional cascade electron transfer (g-C3 N4 → L-Ti3 C2 -R → FePc) induced by the dual junction of FePc/L-Ti3 C2 -R and L-Ti3 C2 -R/g-C3 N4 makes the Fe center electron-rich and therefore facilitates the adsorption of O2 in the oxygen reduction reaction (ORR). Moreover, the electron transfer between FePc and MXene is facilitated by the axial Fe─O coordination interaction of Fe with the OH in alkalized MXene nanosheets (L-Ti3 C2 -OH). As a result, FePc/L-OH/CN exhibits an impressive ORR activity with a half-wave potential (E1/2 ) of 0.92 V, which is superior over the catalysts with a single junction and the state-of-the-art Pt/C (E1/2 = 0.85 V). This work provides a broad idea for deep regulation of electronic state by the unidirectional cascade multi-step charge transfer and can be extended to other proton-coupled electron transfer processes.

Fabrication of Bi2O3/Bismuth Titanates Modified with Metal-Organic Framework-In2S3/CdIn2S4 Materials for Electrocatalytic H2 Production and Its Photoactivity

Compositional and structural elucidation of the materials is important to know their properties, chemical stability, and electro-photoactivity. The heterojunction electrocatalyst and photocatalyst activity could open a new window for solving the most urgent environmental and energy problems. Here, for the first time, we have designed and fabricated Bi2O3/bismuth titanates modified with MOF-In2S3/CdIn2S4 materials by a stepwise process. The detailed structural elucidation and formation of mixed composite phases were studied in detail. It has been found that the formed composite was efficiently utilized for the electrocatalytic H2 production reaction and the photocatalytic degradation of tetracycline. XRD patterns for the metal-organic framework-In2S3 showed a main compound of MOF, and it was assigned to a MIL-53 MOF phase, with a monoclinic structure. The addition of CdCl2 onto the MOF-In2S3 phase effectively produced a CdIn2S4 flower platform on the MOF rods. The uniform dispersion of the bismuth titanates in MOF-In2S3/CdIn2S4 materials is detected by mapping of elements obtained by dark-field HAADF-STEM. Finally, the predictions of how to integrate experiments and obtain structural results more effectively and their common development in new heterojunctions for electro-/photocatalytic applications are presented.

Restraining Interfacial Cu2+ by using Amorphous SnO2 as Sacrificial Protection Boosts CO2 Electroreduction

The electrochemical carbon dioxide reduction reaction (CO2 RR) to formate is of great interest in the field of electrochemical energy. Cu-based material is an appealing electrocatalyst for the CO2 RR. However, retaining Cu2+ under the high cathodic potential of CO2 RR remains a great challenge, leading to low electrocatalytic selectivity, activity, and stability. Herein, inspired by corrosion science, a sacrificial protection strategy to stabilize interfacial crystalline CuO through embedding of active amorphous SnO2 (c-CuO/a-SnO2 ) is reported, which greatly boosts the electrocatalytic sensitivity, activity, and stability for CO2 RR to formate. The as-made hybrid catalyst can achieve superior high selectivity for CO2 RR to formate with a remarkable Faradaic efficiency (FE) of 96.7%, and a superhigh current density of over 1 A cm-2 that far outperforms industrial benchmarks (FE > 90%, current density > 300 mA cm-2 ). In situ X-ray absorption spectroscopy (XAS) and X-ray diffractionexperimental and theoretical calculation results reveal that the broadened s-orbital in interfacial a-SnO2 offers the lower orbital for extra electrons than Cu2+ , which can effectively retain nearby Cu2+ , and the high active interface significantly lowers the energy barrier of the limited step (* CO2 → * HCOO) and enhances the selectivity and activity for CO2 RR to formate.

InBi Bimetallic Sites for Efficient Electrochemical Reduction of CO2 to HCOOH

Formic acid is receiving intensive attention as being one of the most progressive chemical fuels for the electrochemical reduction of carbon dioxide. However, the majority of catalysts suffer from low current density and Faraday efficiency. To this end, an efficient catalyst of In/Bi-750 with InOx nanodots load is prepared on a two-dimensional nanoflake Bi2 O2 CO3 substrate, which increases the adsorption of * CO2 due to the synergistic interaction between the bimetals and the exposure of sufficient active sites. In the H-type electrolytic cell, the formate Faraday efficiency (FE) reaches 97.17% at -1.0 V (vs reversible hydrogen electrode (RHE)) with no significant decay over 48 h. A formate Faraday efficiency of 90.83% is also obtained in the flow cell at a higher current density of 200 mA cm-2 . Both in-situ Fourier transform infrared spectroscopy (FT-IR) and theoretical calculations show that the BiIn bimetallic site can deliver superior binding energy to the * OCHO intermediate, thereby fundamentally accelerating the conversion of CO2 to HCOOH. Furthermore, assembled Zn-CO2 cell exhibits a maximum power of 6.97 mW cm-1 and a stability of 60 h.

Anion Exchange Facilitates the In Situ Construction of Bi/BiO Interfaces for Enhanced Electrochemical CO2 -to-Formate Conversion Over a Wide Potential Window

Electrochemical reduction of CO2 (CO2 RR) into value-added products is a promising strategy to reduce energy consumption and solve environmental issues. Formic acid/formate is one of the high-value, easy-to-collect, and economically viable products. Herein, the reconstructed Bi2 O2 CO3 nanosheets (BOCR NSs) are synthesized by an in situ electrochemical anion exchange strategy from Bi2 O2 SO4 as a pre-catalyst. The BOCR NSs achieve a high formate Faradaic efficiency (FEformate ) of 95.7% at -1.1 V versus reversible hydrogen electrode (vs. RHE), and maintain FEformate above 90% in a wide potential range from -0.8 to -1.5 V in H-cell. The in situ spectroscopic studies reveal that the obtained BOCR NSs undergo the anion exchange from Bi2 O2 SO4 to Bi2 O2 CO3 and further promote the self-reduction to metallic Bi to construct Bi/BiO active site to facilitate the formation of OCHO* intermediate. This result demonstrates anion exchange strategy can be used to rational design high performance of the catalysts toward CO2 RR.

Al-Doped Octahedral Cu2O Nanocrystal for Electrocatalytic CO2 Reduction to Produce Ethylene

Ethylene is an ideal CO2 product in an electrocatalytic CO2 reduction reaction (CO2RR) with high economic value. This paper synthesised Al-doped octahedral Cu2O (Al-Cu2O) nanocrystal by a simple wet chemical method. The selectivity of CO2RR products was improved by doping Al onto the surface of octahedral Cu2O. The Al-Cu2O was used as an efficient electrocatalyst for CO2RR with selective ethylene production. The Al-Cu2O exhibited a high % Faradic efficiency (FEC2H4) of 44.9% at -1.23 V (vs. RHE) in CO2 saturated 0.1 M KHCO3 electrolyte. Charge transfer from the Al atom to the Cu atom occurs after Al doping in Cu2O, optimizing the electronic structure and facilitating CO2RR to ethylene production. The DFT calculation showed that the Al-Cu2O catalyst could effectively reduce the adsorption energy of the *CHCOH intermediate and promote the mass transfer of charges, thus improving the FEC2H4. After Al doping into Cu2O, the center of d orbitals shift positively, which makes the d-band closer to the Fermi level. Furthermore, the density of electronic states increases due to the interaction between Cu atoms and intermediates, thus accelerating the electrochemical CO2 reduction process. This work proved that the metal doping strategy can effectively improve the catalytic properties of Cu2O, thus providing a useful way for CO2 cycling and green production of C2H4.

Interfacial Electronic Interaction in In2O3/Poly(3,4-ethylenedioxythiophene)-Modified Carbon Heterostructures for Enhanced Electroreduction of CO2 to Formate

Formate, as an important chemical raw material, is considered to be one of the most promising products for industrialization among CO₂ electroreduction reaction (CO₂RR) products, but it still suffers from poor selectivity and a low formation rate at a high current density on account of the competitory hydrogen evolution reaction. Herein, the heterogeneous nanostructure was constructed by anchoring In₂O₃ nanoparticles on poly(3,4-ethylenedioxythiophene) (PEDOT)-modified carbon black (In₂O₃/PC), in which the PEDOT polymer interface layer could immobilize In₂O₃ nanoparticles and obtain a notable reduction in electron transfer resistance among the In₂O₃ particles, showing a 27% increase in the total electron transfer rate. The optimized In₂O₃/PC with rich heterogeneous interfaces selectively reduced CO₂ to formate with a high FE of 95.4% and a current density of 251.4 mA cm^-2 under -1.18 V vs RHE. Also, the formate production rate for In₂O₃/PC was up to 7025.1 μmol h^-1 cm^-2, surpassing most previously reported CO₂RR catalysts. The in situ XRD results revealed that In₂O₃ particles were reduced to metallic indium (In) as catalytic active sites during CO₂RR. DFT calculations verified that a strong interface interaction between In sites and PC induced electron transfer from In sites to PC, which could optimize the charge distribution of active sites, accelerate electron transfer, and elevate the p-band center of In sites toward the Fermi level, thereby lowering the adsorption energy of *OCHO intermediates for CO₂ conversion to formate.

Indium Cyanamide for Industrial-Grade CO2 Electroreduction to Formic Acid

Developing industrial-grade electroreduction of CO2 to produce formate (HCOO-)/formic acid (HCOOH) depends on highly active electrocatalysts. However, structural changes due to the inevitable self-reduction of catalysts result in severe long-term stability issues at industrial-grade current density. Herein, linear cyanamide anion ([NCN]2-)-constructed indium cyanamide nanoparticles (InNCN) were investigated for CO2 reduction to HCOO- with a Faradaic efficiency of up to 96% under a partial current density (jformate) of 250 mA cm-2. Bulk electrolysis at a jformate of 400 mA cm-2 requires only -0.72 VRHE applied potential with iR correction. It also achieves continuous production of pure HCOOH at ∼125 mA cm-2 for 160 h. The excellent activity and stability of InNCN are attributed to its unique structural features, including strongly σ-donating [NCN]2- ligands, the potential structural transformation of [N═C═N]2- and [N≡C-N]2-, and the open framework structure. This study affirms metal cyanamides as promising novel materials for electrocatalytic CO2 reduction, broadening the variety of CO2 reduction catalysts and the understanding of structure-activity relationships.

Size Effects of Highly Dispersed Bismuth Nanoparticles on Electrocatalytic Reduction of Carbon Dioxide to Formic Acid

Electrocatalytic reduction of carbon dioxide into value-added chemical fuels is a promising way to achieve carbon neutrality. Bismuth-based materials have been considered as favorable electrocatalysts for converting carbon dioxide to formic acid. Moreover, size-dependent catalysis offers significant advantages in catalyzed heterogeneous chemical processes. However, the size effects of bismuth nanoparticles on formic acid production have not been fully explored. Here, we prepared Bi nanoparticles uniformly supported on porous TiO₂ substrate electrocatalytic materials by in situ segregation of the Bi element from Bi₄Ti₃O₁₂. The Bi-TiO₂ electrocatalyst with Bi nanoparticles of 2.83 nm displays a Faradaic efficiency of greater than 90% over a wide potential range of 400 mV. Theoretical calculations have also demonstrated subtle electronic structural evolutions induced by the size variations of Bi nanoparticles, where the 2.83 nm Bi nanoparticles display the most active p-band and d-band centers to guarantee high electroactivity toward CO₂RR.

From Traditional to New Benchmark Catalysts for CO2 Electroreduction

In the last century, conventional strategies pursued to reduce or convert CO₂ have shown limitations and, consequently, have been pushing the development of innovative routes. Among them, great efforts have been made in the field of heterogeneous electrochemical CO₂ conversion, which boasts the use of mild operative conditions, compatibility with renewable energy sources, and high versatility from an industrial point of view. Indeed, since the pioneering studies of Hori and co-workers, a wide range of electrocatalysts have been designed. Starting from the performances achieved using traditional bulk metal electrodes, advanced nanostructured and multi-phase materials are currently being studied with the main goal of overcoming the high overpotentials usually required for the obtainment of reduction products in substantial amounts. This review reports the most relevant examples of metal-based, nanostructured electrocatalysts proposed in the literature during the last 40 years. Moreover, the benchmark materials are identified and the most promising strategies towards the selective conversion to high-added-value chemicals with superior productivities are highlighted.

Recent Progress and Perspectives on Photocathode Materials for CO2 Catalytic Reduction

The continuous consumption of fossil energy and excessive emissions of carbon dioxide (CO₂) have caused a serious energy crisis and led to the greenhouse effect. Using natural resources to convert CO₂ into fuel or high-value chemicals is considered to be an effective solution. Photoelectrochemical (PEC) catalysis utilizes abundant solar energy resources, combined with the advantages of photocatalysis (PC) and electrocatalysis (EC), to achieve efficient CO₂ conversion. In this review, the basic principles and evaluation criteria, of PEC catalytic reduction to CO₂ (PEC CO₂RR), are introduced. Next, the recent research progress on typical kinds of photocathode materials for CO₂ reduction are reviewed, and the structure-function relationships between material composition/structure and activity/selectivity are discussed. Finally, the possible catalytic mechanisms and the challenges of using PEC to reduce CO₂ are proposed.

Facile construction of robust Ru-Co3O4 Mott-Schottky catalyst enabling efficient dehydrogenation of ammonia borane for hydrogen generation

Developing efficient catalysts for the dehydrogenation of ammonia borane (AB) is important for the safe storage and controlled release of hydrogen, but it is a challenging task. In this study, we designed a robust Ru-Co₃O₄ catalyst using the Mott-Schottky effect to induce favorable charge rearrangement. The self-created electron-rich Co₃O₄ and electron-deficient Ru sites at heterointerfaces are indispensable for the activation of the B-H bond in NH₃BH₃ and the OH bond in H₂O, respectively. The synergistic electronic interaction between the electron-rich Co₃O₄ and electron-deficient Ru sites at the heterointerfaces resulted in an optimal Ru-Co₃O₄ heterostructure that exhibited outstanding catalytic activity for the hydrolysis of AB in the presence of NaOH. The heterostructure had an extremely high hydrogen generation rate (HGR) of 12238 mL min^-1 g_cat^-1 and an expected high turnover frequency (TOF) of 755 mol_H2 mol_Ru^-1 min^-1 at 298 K. The activation energy needed for the hydrolysis was low (36.65 kJ mol^-1). This study opens up a new avenue for the rational design of high-performance catalysts for AB dehydrogenation based on the Mott-Schottky effect.

Bi2S3 nanorods grown on multiwalled carbon nanotubes as highly active catalysts for CO2 electroreduction to formate

Bi-based materials are promising electrocatalysts for CO₂ reduction but one of the key technological hurdles is the design of stable, active and affordable Bi-based catalysts over a wide potential range. Herein, Bi₂S₃/CNTs nanocomposites are constructed by anchoring bismuth sulfide (Bi₂S₃) nanorods onto the multiwalled carbon nanotubes (CNTs) and utilizing them in electrocatalytic CO₂ reduction. CNTs, as a support, not only guarantee the conductivity and dispersibility of Bi₂S₃ nanorods but also improve the electrolyte infiltration and optimize the electronic structure of the Bi₂S₃. As expected, the Bi₂S₃/CNTs nanocomposite exhibits a faradaic efficiency for HCOO^- (FE_HCOO-) of 99.3% with a current density of -20.3 mA cm^-2 at -0.91 V vs. RHE. The FE_HCOO- is stably maintained at over > 91% in a wide potential window from -0.71 V to -1.31 V. Theoretical calculation analyses reveal that the strong interaction between Bi₂S₃ and CNTs is conductive to decreasing the energy barrier of *OCHO, stabilizing the intermediate *OCHO, and inhibiting the hydrogen evolution reaction. The current study provides an insightful understanding of the mechanism of the CO₂ electroreduction reaction, and paves a new way for developing superior and affordable electrocatalysts.

One-Step Phase Separation for Core-Shell Carbon@Indium Oxide@Bismuth Microspheres with Enhanced Activity for CO2 Electroreduction to Formate

It is a substantial challenge to construct electrocatalysts with high activity, good selectivity, and long-term stability for electrocatalytic reduction of carbon dioxide to formic acid. Herein, bismuth and indium species are innovatively integrated into a uniform heterogeneous spherical structure by a neoteric quasi-microemulsion method, and a novel C@In₂ O₃ @Bi₅₀ core-shell structure is constructed through a subsequent one-step phase separation strategy due to melting point difference and Kirkendall effect with the nano-limiting effect of the carbon structure. This core-shell C@In₂ O₃ @Bi₅₀ catalyst can selectively reduce CO₂ to formate with high selectivity (≈90% faradaic efficiency), large partial current density (24.53 mA cm^-2 at -1.36 V), and long-term stability (up to 14.5 h), superior to most of the Bi-based catalysts. The hybrid Bi/In₂ O₃ interfaces of core-shell C@In₂ O₃ @Bi will stabilize the key intermediate HCOO* and suppress CO poisoning, benefiting the CO₂ RR selectivity and stability, while the internal cavity of core-shell structure will improve the reaction kinetics because of the large specific surface area and the enhancement of ion shuttle and electron transfer. Furthermore, the nano-limited domain effect of outmost carbon prevent active components from oxidation and agglomeration, helpful for stabilizing the catalyst. This work offers valuable insights into core-shell structure engineering to promote practical CO₂ conversion technology.

Recent Advances in Defect-Engineered Transition Metal Dichalcogenides for Enhanced Electrocatalytic Hydrogen Evolution: Perfecting Imperfections

Switching to renewable, carbon-neutral sources of energy is urgent and critical for climate change mitigation. Despite how hydrogen production by electrolyzing water can enable renewable energy storage, current technologies unfortunately require rare and expensive platinum group metal electrocatalysts, which limit their economic viability. Transition metal dichalcogenides (TMDs) are low-cost, earth-abundant materials that possess the potential to replace platinum as the hydrogen evolution catalyst for water electrolysis, but so far, pristine TMDs are plagued by poor catalytic performances. Defect engineering is an attractive approach to enhance the catalytic efficiency of TMDs and is not subjected to the limitations of other approaches like phase engineering and surface structure engineering. In this minireview, we discuss the recent progress made in defect-engineered TMDs as efficient, robust, and low-cost catalysts for water splitting. The roles of chalcogen atomic defects in engineering TMDs for improvements to the hydrogen evolution reaction (HER) are summarized. Finally, we highlight our perspectives on the challenges and opportunities of defect engineering in TMDs for electrocatalytic water splitting. We hope to provide inspirations for designing the state-of-the-art catalysts for future breakthroughs in the electrocatalytic HER.

Ag-induced Phase Transition of Bi2 O3 Nanofibers for Enhanced Energy Conversion Efficiency towards Formate in CO2 Electroreduction

Bi-based electrocatalysts have been widely investigated in the CO₂ reduction reaction (CO₂ RR) for the formation of formate. However, it remains a challenge to achieve high Faradaic efficiency (FE) and industrial current densities at low overpotentials for obtaining both high formate productivity and energy efficiency (EE). Herein, we report an Ag-Bi₂ O₃ hybrid nanofiber (Ag-Bi₂ O₃ ) for highly efficient electrochemical reduction of CO₂ to formate. Ag-Bi₂ O₃ exhibits a formate FE of >90% for current densities from -10 to -250 mA ⋅ cm^-2 and attains a yield rate of 11.7 mmol ⋅ s^-1  ⋅ m^-2 at -250 mA ⋅ cm^-2 . Moreover, Ag-Bi₂ O₃ increased the EE (52.7%) by nearly 10% compared to a Bi₂ O₃ only counterpart. Structural characterization and in-situ Raman results suggest that the presence of Ag induced the conversion of Bi₂ O₃ from a monoclinic phase (α-Bi₂ O₃ ) to a metastable tetragonal phase (β-Bi₂ O₃ ) and accelerated the formation of active metallic Bi at low overpotentials (at > -0.3 V), which together contributes to the highly efficient formate formation.

Bionic Construction of Helical Bi2 O3 Microfibers for Highly Efficient CO2 Electroreduction

Helical Bi₂ O₃ microfibers (HBM) were prepared with the assistance of cotton template through a simple heating treatment in air. This twisted structure induced the lattice strains, enriched the oxygen vacancies of Bi₂ O₃ , and promoted the sufficient exposure of active sites simultaneously, thus performing outstanding activity and selectivity as catalyst for CO₂ electroreduction to formate. The faradaic efficiency (FE) of formate reached 100.4±1.9 % at -0.90 V vs. reversible hydrogen electrode (RHE) in an H-cell, and the partial current density was boosted to 226 mA cm^-2 with FE_formate of 96 % at -1.08 V vs. RHE in a flow cell. This work may open a new era for construction of metal oxide fibers by bionic strategy as high-performance electrocatalysts.

Nitrogen-Doped Bismuth Nanosheet as an Efficient Electrocatalyst to CO2 Reduction for Production of Formate

Electrochemical CO₂ reduction (CO₂RR) to produce high value-added chemicals or fuels is a promising technology to address the greenhouse effect and energy challenges. Formate is a desirable product of CO₂RR with great economic value. Here, nitrogen-doped bismuth nanosheets (N-BiNSs) were prepared by a facile one-step method. The N-BiNSs were used as efficient electrocatalysts for CO₂RR with selective formate production. The N-BiNSs exhibited a high formate Faradic efficiency (FE_formate) of 95.25% at -0.95 V (vs. RHE) with a stable current density of 33.63 mA cm^-2 in 0.5 M KHCO₃. Moreover, the N-BiNSs for CO₂RR yielded a large current density (300 mA cm^-2) for formate production in a flow-cell measurement, achieving the commercial requirement. The FE_formate of 90% can maintain stability for 14 h of electrolysis. Nitrogen doping could induce charge transfer from the N atom to the Bi atom, thus modulating the electronic structure of N-Bi nanosheets. DFT results demonstrated the N-BiNSs reduced the adsorption energy of the *OCHO intermediate and promoted the mass transfer of charges, thereby improving the CO₂RR with high FE_formate. This study provides a valuable strategy to enhance the catalytic performance of bismuth-based catalysts for CO₂RR by using a nitrogen-doping strategy.

The Critical Role of Initial/Operando Oxygen Loading in General Bismuth-Based Catalysts for Electroreduction of Carbon Dioxide

Operando reconstruction of solid catalyst into a distinct active state frequently occurs during electrocatalytic processes. The correlation between initial and operando states, if ever existing, is critical for the understanding and precise design of a catalytic system. Inspired by recently established intermediate metallic state of Bi-based catalysts during electrocatalytic carbon dioxide reduction (CO₂RR), here we investigate a series of Bi oxide catalysts (Bi, Bi₂O₃, BiO₂) and demonstrate that the operando surface/subsurface oxygen loading, positively correlated to the initial oxygen content, plays a critical role in determining Bi-based CO₂RR performance. Higher initial oxygen loading indicates a better electrocatalytic efficiency. Further analysis shows that this conclusion generally applies to all Bi-based electrocatalysts reported up to date. Following this principle, cost-effective BiO₂ nanocrystals demonstrated the highest formate Faradaic efficiency (FE) and current density compared to Bi/Bi₂O₃, further allowing a pair-electrolysis system with 800 mA/cm² current density and an overall 175% FE for formate production.

Metal-Organic Framework-Derived BiIn Bimetallic Oxide Nanoparticles Embedded in Carbon Networks for Efficient Electrochemical Reduction of CO2 to Formate

Bismuth-based catalysts exhibit excellent activity and selectivity for the electroreduction of carbon dioxide (CO₂). However, single-component bismuth-based catalysts are not satisfactory for the electrochemical reduction of CO₂ to formic acid, mainly due to their high hydrogen production, low electrical conductivity, and small catalytic current density. Herein, we used a coordination strategy to recombine Bi and In at the molecular level to form Bi/In bimetallic metal-organic frameworks (MOFs), which were then calcined to obtain MOF-derived Bi/In bimetallic oxide nanoparticles embedded in carbon networks. Thanks to the synergistic effect of bimetallic components, high specific surface area, suitable pore size distribution, and high electrical conductivity of the carbon network, the material exhibits excellent activity and selectivity for electroreduction of CO₂ to formate. In H-type electrolyzers, the formate Faradaic efficiency reaches 91% at -0.9 V (vs RHE) and does not decrease significantly within 48 h. In situ Fourier transform infrared spectroscopy confirms the reaction intermediates and reveals that CO₂ electroreduction is dominant by the *OCHO pathway.