Phase Interface Regulating on Amorphous/Crystalline Bismuth Catalyst for Boosted Electrocatalytic CO2 Reduction to Formate

Amorphous/Crystalline Interface of Bi/Bi4NbO8Cl Heterostructure for Improved Piezo-Photocatalysis

Efficient separation of photogenerated charges at the surface of photocatalysts is vital for achieving high photocatalytic activity. Here, a Bi/Bi4NbO8Cl heterostructure piezo-photocatalyst with an amorphous/crystalline interface (acBi/BNC) is prepared by in situ reduction using Bi4NbO8Cl as a self-sacrificial template. This ingenious design synergistically utilizes the advantages of the amorphous/crystalline interface structure, localized surface plasmon resonance effect, and piezoelectric field. The formation of amorphous/crystalline interfaces induces the generation of oxygen vacancies, and subsequently lattice distortions, thus improving the piezoelectric properties. Theoretical and experimental results demonstrate that the combination of piezoelectric field and amorphous/crystalline interface promotes the effective separation and migration of photogenerated charges between the bulk and surface of the catalysts. Under simultaneous light and ultrasound, the optimal heterostructure (acBi/BNC-3) exhibit superior photodegradation efficiency of tetracycline reached 80% within 5 min, and the reaction rate (2.78 × 10-1 min-1) is 7.8 and 5.4 times that of pure Bi4NbO8Cl (BNC) and crystalline Bi/Bi4NbO8Cl (cBi/BNC), respectively. Furthermore, the piezo-photocatalytic tetracycline degradation efficiency surpasses those under individual photocatalysis and piezocatalysis conditions. This work provides a novel rational design to improve the spatial charge separation of Bi-based catalysts and prepare high-performance piezo-photocatalysts via interface engineering.

Progress in Catalysts for Formic Acid Production by Electrochemical Reduction of Carbon Dioxide

Utilising renewable energy to drive the conversion of carbon dioxide into more valuable products can effectively alleviate the energy crisis and protect the environment while actively responding to the policy of "carbon peaking and carbon neutrality". Additionally, formic acid/formate is one of the most promising and commercially valuable products of the electrocatalytic CO2 reduction reaction (ECO2RR) as well as a nonhazardous material for hydrogen storage. With the continuous progress in the field of electrocatalytic CO2 reduction to formic acid/formate (ECO2RF), various electrocatalysts with excellent performance have been developed. In this paper, first, the reaction mechanism of ECO2RF is briefly summarised, and then the recent research progress for various catalysts for ECO2RF, including metal-based catalysts, carbon-based material catalysts, metal-organic framework catalysts, covalent organic framework catalysts, and molecular catalysts, is reviewed. Finally, the current challenges and future perspectives of ECO2RF are discussed and presented.

Modulating the Active Sites of VS2 by Mn Doping for Highly Selective CO2 Electroreduction to Methanol in a Flow Cell

Methanol is a valuable liquid C1 product in CO2 electroreduction (CO2ER); however, it is hard to achieve high selectivity and a large current density simultaneously. In this work, we construct Mn2+-doped VS2 multilayer nanowafers applied in a flow cell to yield methanol as a single liquid product to tackle this challenge. Mn doping adjusts the electronic structure of VS2 and concurrently introduces sulfur vacancies, forming a critical *COB intermediate and facilitating its sequential hydrogenation to methanol. The optimal Mn4.8%-VS2 exhibits methanol Faradic efficiencies of more than 60% over a wide potential range of -0.4 to -0.8 V in a flow cell, of which the maximal value is 72.5 ± 1.1% at -0.6 V along with a partial current density of 74.3 ± 1.1 mA cm-2. This work opens an avenue to rationally design catalysts for engineering C1 intermediates toward CO2ER to a single liquid methanol in a flow cell.

Crystalline CdS/Amorphous Cd(OH)2 Composite for Electrochemical CO2 Reduction to CO in a Wide Potential Window

Electrochemical CO2 reduction is a promising method for converting atmospheric CO2 into valuable low-carbon chemicals. In this study, a crystalline cadmium sulfide/amorphous cadmium hydroxide composite was successfully deposited on the carbon paper substrate surface by in-situ chemical bath deposition (named as c-CdS/a-Cd(OH)2/CP electrodes) for the efficient electrochemical CO2 reduction to produce CO. The c-CdS/a-Cd(OH)2/CP electrode exhibited high CO Faradaic efficiencies (>90 %) under a wide potential window of 1.0 V, with the highest value reaching ~100 % at the applied potential ranging from -2.16 V to -2.46 V vs. ferrocene/ferrocenium (Fc/Fc+), superior to the crystalline counterpart c-CdS/CP and c-CdS/c-Cd(OH)2@CP electrodes. Meanwhile, the CO partial current density reached up to 154.7 mA cm-2 at -2.76 V vs. Fc/Fc+ on the c-CdS/a-Cd(OH)2/CP electrode. The excellent performance of this electrode was mainly ascribed to its special three-dimensional structure and the introduction of a-Cd(OH)2. These structures could provide more active sites, accelerate the charge transfer, and enhance adsorption of *COOH intermediates, thereby improving the CO selectivity. Moreover, the electrolytes consisting of 1-butyl-3-methylimidazolium tetrafluoroborate and acetonitrile also enhanced the reaction kinetics of electrochemical CO2 reduction to CO.

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.

Anion-Mediated In Situ Reconstruction of the Bi2MoO6 Precatalyst for Enhanced Electrochemical CO2 Reduction over a Wide Potential Window

Electrochemical CO2 reduction reaction (eCO2RR) is a viable approach to achieve carbon neutrality. Bismuth-based electrocatalysts demonstrate exceptional selectivity in CO2-to-formate conversion, but their reconstruction mechanisms during the eCO2RR remain elusive. Herein, the reconstruction processes of bismuth molybdate (Bi2MoO6) nanoplates are elucidated during the eCO2RR. Operando and ex situ measurements reveal the in situ partial reduction of Bi2MoO6 to Bi metal, forming Bi@Bi2MoO6 at negative potentials. Meanwhile, CO32- ions in the electrolyte spontaneously exchange with MoO42- in Bi2MoO6. The obtained Bi@Bi2MoO6/Bi2O2CO3 delivers a formate Faradaic efficiency (FE) of 95.2% at -1.0 V. Notably, high formate FEs (>90%) are maintained within a wide 500 mV window. Although computational calculations indicate a higher energy barrier for *OCHO formation on Bi2O2CO3, the prevention of excessive reduction to metal Bi significantly enhances long-term stability. Furthermore, the CO32- ion exchange process occurs in various 2D Bi-containing precatalysts, which should be emphasized in further studies.