Reduced Mass Transfer Resistance Research Articles

Positively charged nanofiltration membranes with gradient structures for enhancing separation properties

Creating a gradient structure in a separation layer is an effective approach for enhancing separation performance of thin film composite membranes. Here we present the preparation of a positively charged nanofiltration membrane with a gradient structure. An inner layer consisting of a loose polyester separation layer with large pores was formed through the interfacial polymerization (IP) reaction between triethanolamine (TEA) and trimesoyl chloride (TMC). And a dense and thin top layer composed of a polyamide separation layer was obtained by secondary interfacial polymerization (SIP) reaction using polyethyleneimine (PEI) along with unreacted TMC and residual acyl chloride groups of IP reaction. The influences of TEA concentration, PEI concentration and SIP time on the physicochemical properties and separation performances of the membrane were systematically analyzed. Our results show that the presence of the gradient structure optimized mass transfer pathways and reduced mass transfer resistance, resulting in significantly improved permeability of 13.0 ± 0.5 L·m−2·h−1·bar−1 (over 3 times compared with control-PEI), high MgCl2 rejection of 91.7 ± 0.6 %, and an excellent stability and anti-fouling performance. Our work provides valuable insights and guidance for developing high-performance positively charged NF membrane with gradient structures.

Superior Heat and Mass Transfer Performance of Bionic Wick with Finger-like Pores Inspired by the Stomatal Array of Natural Leaf.

The thermal management of electronics has gained significant attention, with loop heat pipes (LHPs) emerging as an attractive solution for heat dissipation. The heat transfer performance of LHPs is influenced by the heat and mass transfer processes within the wick. However, designing the pore diameter of the wick is challenging due to the different requirements of flow resistance and capillary force. Specifically, the working fluid needs large pores to reduce resistance, while the liquid suction requires small pores to provide a large capillary force. To address this issue, we drew inspiration from the stomatal array of natural leaves used for transpiration and developed an alumina ceramic bionic wick with finger-like pores using the phase-inversion tape casting method. The finger-like pores in the wick resemble the straight hole structure of stomata, which increases the gas-liquid interface area within the wick. This design allows for timely discharge of water vapor generated by boiling, thereby reducing mass transfer resistance. Additionally, numerous micrometer-sized small pores surrounding the finger-like pores provide sufficient capillary force to replenish liquid for the gas-liquid evaporation interface. Experimental results demonstrate that the introduction of finger-like pores in the wick increases gas and water permeabilities by 2.4 and 5.2 times, respectively. Furthermore, the superior heat and mass transfer performance of the bionic wick was demonstrated with an LHP. This work effectively addresses the conflicting demands of capillary force and flow resistance, enhancing the heat transfer performance of LHPs, which holds great promise for addressing heat dissipation challenges in high power density electronic chips and has potential applications in aviation, aerospace, and microelectronics for efficient thermal management.

A Highly Integrated Component with Tri‐Part Significantly Enhances Fuel Cell Power Density by Reducing Mass Transfer Resistance and Excellent Humidity Tolerance

AbstractTraditional flow fields and gas diffusion layers (GDL) suffer from water flooding at the rib contact surface, resulting in mass transfer obstruction. Herein, an integrated component (i‐component) with tri‐part of the flow field, gas diffusion backing, and the microporous layer is prepared using the filter molding method to prevent flooding at the rib. The i‐component with micro‐tunnels is more compact than traditional fuel cells and has no distinct interface, significantly enhancing fuel cell performance, reducing mass transfer resistance, and improving water management. Remarkably, the mass transfer resistance of the i‐components is reduced by six times, accompanied by a 50% increase in power density (1.63 W cm−2) and a 146% surge in volume‐specific power (24 500 W L−1). Additionally, it exhibits excellent humidity tolerance in the relative humidity range of 30–100%. This method achieves large‐area i‐component (388 cm2) preparation in 0.5 h at 350 °C, which reduces time by dozens and energy consumption by over 100 times compared to the traditional method for preparing commercial GDL. The i‐component significantly enhances the mass transfer and water management capabilities of fuel cells. Hence, the i‐component provides new strategies for next‐generation fuel cells, water electrolysis, flow battery, carbon dioxide reduction, etc.

An intelligent dual stimuli-responsive Pickering emulsion for highly efficiently producing waste frying oil-based biodiesel

Directionally converting waste frying oil (WFO) to biodiesel is not only a crucial strategy for its clean and efficient utilization, but also a promising alternative for the large-scale substitution of petroleum-based fuels. However, the challenge of reducing mass transfer resistance between the alcohol/oil bi-liquid phases remains a major obstacle in the industrialization of WFO-based biodiesel (WFOBB). Additionally, both rapid emulsification and efficient demulsification still present bottlenecks that need to be addressed in emulsion reaction. Herein, the present study successfully demonstrates the fabrication of a novel Pickering interfacial catalyst with immobilized Brønsted-Lewis di-acid functionalized ionic liquids and photosensitizer (P(5[DVB]-[SP]-[ILs-2FeCl3])@SiO2@Fe3O4) through layer-by-layer self-assembly. This novel Pickering interfacial catalyst efficiently constructed an intelligent magneto-optical dual stimuli-responsive Pickering emulsion. The intelligent Pickering emulsion enables precise control over amphiphilic interfacial catalyst using Vis-light regulation, thereby significantly enhancing mass transfer in the biphasic methanol-WFO system while providing an optimal hydrophobic micro-environment for highly efficient WFOBB production. The intelligent Pickering catalyst exhibits exceptional catalytic performance in achieving a 92.4% yield of WFOBB, which is currently the highest reported value under similar conditions. Furthermore, the efficient demulsification and separation of this Pickering interfacial catalyst could be achieved through the synergistic effect of UV-irradiation-induced hydrophilicity and its magnetic property. These findings present a new avenue for advancing the development of WFOBB technologies, while also offering promising prospects for industrial applications of Pickering emulsion systems.

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Three‐dimensionally ordered macro/mesoporous carbon material is a new material with interconnected macroporous structure and rich meso/micropores. The interconnected macroporous structure can effectively reduce mass transfer resistance and improve the contact efficiency between reactants and active sites during the catalytic process. More details are discussed in the article by Sun et al. on page 164—170. image

Experimental and molecular dynamics simulation study of toluene absorption by nanofluids

It is well known that the emission of volatile organic compounds (VOCs) is a significant threat to human health and the ecological environment, and toluene is a typical representative of aromatic VOCs, whose elimination makes an important contribution to the prevention and control of air pollution. Absorption is the classical process to eliminate air pollutants, but the application of absorption is often constrained by absorbent and gas-liquid mass transfer. In recent years, process intensification has become an important development in the chemical industry, and nanotechnology can effectively reduce mass transfer resistance and improve gas-liquid mass transfer effectiveness. This work aims to evaluate the effect of adding nanoparticles on the gas-liquid mass transfer process. The effects of TiO2, Al2O3, and SiO2 nanoparticles on the removal of toluene by green solvent low transition temperature mixtures (LTTM) were investigated experimentally and theoretically. The mass transfer enhancement factors of the toluene absorption process were measured at different concentrations and sizes of TiO2, Al2O3, and SiO2 nanoparticles, absorption temperatures and number of cycles. Molecular dynamics (MD) simulations of the microscopic properties of LTTM and toluene were performed. Based on the MD simulation results, the toluene density distribution, interaction energy, radial distribution function, spatial distribution function, and self-diffusion coefficient were calculated, which helped to explain the absorption mechanism of toluene gas. The findings demonstrated that nanoparticles can alter the gas-liquid mass transfer process, and provided a method and theoretical reference for enhancing the toluene absorption process.

Mild and selective catalytic oxidation of 5-HMF to 2,5-FDCA over metal loaded biomass derived graphene oxide using hydrogen peroxide in aqueous media

Biomass-derived graphene oxide-supported metal catalysts (Ru@S-GO, Pd@ S-GO, and Pd/Ru@ S-GO) were produced in a tube furnace with a metal loading of 1 weight percent. All the synthesised nano catalysts were well characterised by XRD, FESEM-EDS, ICP-OES, XPS and FTIR, and applied for the oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-furan dicarboxylic acid (FDCA). Hydrogen peroxide was utilized as the liquid oxidant due to its reduced mass transfer resistance. 5-HMF used in this study was also obtained from biomass. All the operational parameters, such as temperature of the reaction, amount of oxidant, base concentration, and catalyst loading were optimized using Response surface methodology (RSM) based on central composite design (CCD). Ru@S-GO was found to have greater activity and selectivity towards FDCA under benign reaction conditions, and complete conversion of 5-HMF to 2,5-FDCA was accomplished (98.8% yield) over 5 hours of reaction time in an aqueous medium with a lower catalyst loading and reduced metal content.

Constructing Gas Transmission Pathways in Two-Dimensional Composite Material ZIF-8@BNNS Mixed-Matrix Membranes to Enhance CO2/N2 Separation Performance

Two-dimensional (2D) nanomaterials, due to their high aspect ratio and high specific surface area, which provide a more tortuous pathway for larger gas molecules, are frequently used in membrane separation. However, in mixed-matrix membranes (MMMs), the high aspect ratio and high specific surface area of 2D fillers can increase transport resistance, thereby reducing the permeability of gas molecules. In this work, we combine boron nitride nanosheets (BNNS) with ZIF-8 nanoparticles to develop a novel material, ZIF-8@BNNS, to improve both CO2 permeability and CO2/N2 selectivity. Growth of ZIF-8 nanoparticles on the BNNS surface is achieved using an in-situ growth method where the amino groups of BNNS are complexed with Zn2+, creating gas transmission pathways that accelerate CO2 transmission. The 2D-BNNS material acts as a barrier in MMMs to improve CO2/N2 selectivity. The MMMs with a 20 wt.% ZIF-8@BNNS loading achieved a CO2 permeability of 106.5 Barrer and CO2/N2 selectivity of 83.2, surpassing the Robeson upper bound (2008) and demonstrating that MOF layers can efficiently reduce mass transfer resistance and enhance gas separation performance.

A novel lignocellulose pretreatment technology by combining KOH, urea peroxide and organosilane to improve glucose yield

Alkali pretreatments are considered as one of the most popular strategies to pretreat lignocellulose due to its high-efficiency, low-cost, high lignine removing and cellulose content. Nevertheless, glucose concentration obtained from lignocellulose by alkali pretrements still can’t meet biorefinery requirements. Thus, a novel strategy to pretreat lignocellulose by combining KOH, UHP (urea peroxide) and organosilane (KOH-UHP-Si pretreatment) was proposed. This novel strategy solved two difficult problems that seriously affected the combined pretreatment of alkali and advanced oxidant, and then the cellulose relative content and glucose yield were increased by about 2.4 times and 9 times compared with the original straw, about 19% and 20% compared with the alkali (KOH) pretreatment, and about 2.2 times and 3.3 times compared with the advanced oxidation (UHP) pretreatment. After optimizing the pretreatment process, cellulose relative content in corn straw reached 81.4%, and the removal rates of lignin and hemicellulose were increased to 97.3% and 88.13%, respectively. In addition, we illustrated the mechanism of KOH-UHP-Si pretreatment, in which KOH plays the major role, the organosilane suspension and UHP play the auxiliary role. When the organosilane reduced mass transfer resistance in the reaction system, KOH and UHP assisted and promote each other mutually. Besides, we also illustrated the mechanism of urea assisting KOH removal of lignin through quantum chemical calculations. Moreover, the substances contained in wastewater produced by the novel technique could be turned into agricultural fertilizers after being processed simply, and there will be zero emission in the whole process. Our results indicate that KOH-UHP-Si pretreatment was a high efficiency low cost and eco-friendly strategy for lignocellulose pretreatment.

Development of a new rotating photocatalytic reactor for the degradation of hazardous pollutants

Abstract The aim of this study was to develop a new rotating photocatalytic reactor operating in recirculation mode with light sources placed outside the photoreactor vessel. The photoreactor with cylindrical geometry was equipped with four artificial lamps used to simulate solar irradiation (2.4% UVB and 12% UVA; 300–700 nm). The photocatalyst was immobilized on abrasive material used as a support and placed on the central (inner) photoreactor tube, which was connected to a power-driven shaft that allowed rotation at a desired speed. A suitable modification of the commercial TiO2 P25 photocatalyst was carried out to reduce its band gap energy and electron-hole recombination and to extend the visible light response range of TiO2. The main task of this research was to apply the basic principles of process intensification methodology, i.e. to explore the influence of rotational hydrodynamics, which allows good access of reactants to the photocatalyst surface, good irradiation of the photocatalytic surface and reduction of mass transfer resistance, leading to increased process efficiency. The homemade photoreactor was used for the photocatalytic degradation of one of the major types of neonicotinoid insecticides, acetamiprid. The influence of various working conditions, such as initial solution pH, rotation speed, recirculation flow rate and initial concentration of acetamiprid on the photocatalytic degradation process was investigated. The optimum degradation conditions were found at a recirculation flow rate of 200 cm3 min−1 and a rotation speed of 200 rpm, indicating that the mass transfer process strongly contributes to the photocatalytic degradation rate at the conditions used in this study. The results obtained during the photocatalytic degradation of acetamiprid in a rotating photoreactor were compared with those obtained under similar operating conditions in a flat-plate photoreactor, and the corresponding conclusions were drawn based on the performed kinetic analysis.

Surface-Exposed Single-Ni Atoms with Potential-Driven Dynamic Behaviors for Highly Efficient Electrocatalytic Oxygen Evolution.

Trapping the active sites on the exterior surface of hollow supports can reduce mass transfer resistance and enhance atomic utilization. Herein, we report a facile chemical vapor deposition strategy to synthesize single-Ni atoms decorated hollow S/N-doped football-like carbon spheres (Ni SAs@S/N-FCS). Specifically, the CdS@3-aminophenol/formaldehyde is carbonized into S/N-FCS. The gas-migrated Ni species are anchored on the surface of S/N-FCS simultaneously, yielding Ni SAs@S/N-FCS. The obtained catalyst exhibits outstanding performance for alkaline oxygen evolution reaction (OER) with an overpotential of 249 mV at 10 mA cm-2 , a small Tafel slope of 56.5 mV dec-1 , and ultra-long stability up to 166 hours without obvious fading. Moreover, the potential-driven dynamic behaviors of Ni-N4 sites and the contribution of the S dopant at different locations in the matrix to the OER activity are revealed by the operando X-ray absorption spectroscopy and theoretical calculations, respectively.

Surface‐Exposed Single‐Ni Atoms with Potential‐Driven Dynamic Behaviors for Highly Efficient Electrocatalytic Oxygen Evolution

AbstractTrapping the active sites on the exterior surface of hollow supports can reduce mass transfer resistance and enhance atomic utilization. Herein, we report a facile chemical vapor deposition strategy to synthesize single‐Ni atoms decorated hollow S/N‐doped football‐like carbon spheres (Ni SAs@S/N‐FCS). Specifically, the CdS@3‐aminophenol/formaldehyde is carbonized into S/N‐FCS. The gas‐migrated Ni species are anchored on the surface of S/N‐FCS simultaneously, yielding Ni SAs@S/N‐FCS. The obtained catalyst exhibits outstanding performance for alkaline oxygen evolution reaction (OER) with an overpotential of 249 mV at 10 mA cm−2, a small Tafel slope of 56.5 mV dec−1, and ultra‐long stability up to 166 hours without obvious fading. Moreover, the potential‐driven dynamic behaviors of Ni‐N4 sites and the contribution of the S dopant at different locations in the matrix to the OER activity are revealed by the operando X‐ray absorption spectroscopy and theoretical calculations, respectively.

Recent Developments in Activated Carbon Catalysts Based on Pore Size Regulation in the Application of Catalytic Ozonation

Due to its highly developed pore structure and large specific surface area, activated carbon is often used as a catalyst or catalyst carrier in catalytic ozonation. Although the pore structure of activated carbon plays a significant role in the treatment of wastewater and the mass transfer of ozone molecules, the effect is complicated and unclear. Because different application scenarios require catalysts with different pore structures, catalysts with appropriate pore structure characteristics should be developed. In this review, we systematically summarized the current adjustment methods for the pore structure of activated carbon, including raw material, carbonization, activation, modification, and loading. Then, based on the brief introduction of the application of activated carbon in catalytic ozonation, the effects of pore structure on catalytic ozonation and mass transfer are reviewed. Furthermore, we proposed that the effect of pore structure is mainly to provide catalytic active sites, promote free radical generation, and reduce mass transfer resistance. Therefore, large external surface area and reasonable pore size distribution are conducive to catalytic ozonation and mass transfer.

Tailored design of highly permeable polyamide-based nanofiltration membrane via a complex-dissociation regulated interfacial polymerization

Nanofiltration (NF) that can separate neutral/charged solutes is considered as a key industrial technology in water softening and wastewater treatment. However, commercial polyamide (PA) NF membranes, with undesirable surface properties and excessive mass transfer resistance, seriously restrict the permeability and are easily attached by pollutants. In this study, a novel complex-dissociation regulated interfacial polymerization (CDRIP) strategy was proposed to prepare highly permeable polyamide-based (PA-based) NF membranes, in which tannic acid (TA)/Ca(II) complex was in situ formed on substrate surface and then dissociated by sodium citrate (SC) after interfacial polymerization. Interestingly, SC can not only adjust surface properties of PA, such as hydrophilicity and surface charge, but also form water-soluble SC/Ca(II) complexes for constructing additional transport channels within the separation layer to reduce mass transfer resistance. After the dissociation of TA/Ca(II) complex, TA remained on the membrane surface to further regulate the surface properties of separation layer. The results showed that the PA/TA/Ca(II)-SC NF membrane maintained a high Na2SO4 rejection (98.5 %) and a remarkable water permeability of 31.7 L·m−2·h−1·bar−1, which is 2-fold that of the pristine PA NF membrane. Moreover, the prepared NF membrane exhibits favorable operation stability and anti-fouling ability. Therefore, by employing the CDRIP method, the permeability of NF membrane can be further improved almost without sacrificing the rejection of Na2SO4, which provides a green and efficient strategy for the fabrication of high-performance PA-based NF membranes.

Two-dimensional heterogenous channels incorporated by enhanced-surface hydrophilic hollow ZIF-8 nanocrystals for ultrafast water permeation

Two-dimensional (2D) interlayer confined channels of graphene oxide (GO) membrane and their potential for ultrafast water molecules transport behavior have drawn substantial interest for advanced water-related membrane separation process. However, the water transfer pathways along the edge-to-edge slits to interlayer channels of adjacent GO nanosheets are still very tortuous, leading to low-efficiency water permeation. Herein, we designed and prepared hollow zeolitic imidazolate framework-8 nanocrystals with enhanced hydrophilic surface (DP@HZIF-8), and then they were incorporated into GO membrane to introduce more nanofluidic channels. More importantly, the enhanced-surface hydrophilicity could well capture water molecules and make them diffuse along the porous multi-pathways of DP@HZIF-8 and interlayer channels of GO, further reducing mass transfer resistance and improving water transfer efficiency under highly-water chemical potential driving force in membrane microregion. As-prepared DP@HZIF-8/GO membrane on polyethersulfone (PES) substrate with optimum structure showed the pure water flux as high as 32.11 kg m−2 h−1 at 323 K, and meanwhile exhibited superior pervaporation dehydration performance of butanol/water mixture with total flux of 5.32 kg m−2 h−1 and separation factor of 3567 at 343 K, respectively. This work strengthens the understanding of high-efficiency water transport along multi-dimensional heterogenous channels in advanced 2D separation membranes.

Controllable growth of coral-like CuInS2 on one-dimensional SiO2 nanotube with super-hydrophilicity for enhanced photocatalytic hydrogen evolution

Designing a semiconductor photocatalyst with a unique structure is crucial for photocatalytic hydrogen evolution. The adsorption of water molecules is considered to be an important link affecting the photocatalytic activity. Nanoconfined water molecules inside the microporous SiO2 nanotube adsorbed on the active sites boosting the photocatalytic hydrogen evolution compared with the bulk water system. Herein, hydrophilic porous SiO2 hollow nanotubes were prepared through electrospinning fiber membranes as templates. CuInS2 nanoparticles were uniformly deposited on porous SiO2 hollow nanotubes to form CuInS2/SiO2 composites. The unique CuInS2/SiO2 hollow nanotube with a coral structure was prepared. A series of characterization results show that CuInS2 supported on porous SiO2 hollow nanotubes has two advantages. On the one hand, SiO2 has excellent hydrophilicity and can be used as a micro water-collecting reactor to reduce mass transfer resistance. On the other hand, SiO2 reduces the particle size of CuInS2, thus improving the utilization rate of light, and inhibiting electron-hole recombination. The CuInS2/SiO2 with a coral structure exhibited the highest hydrogen production rate of 367.00 μmol g−1 h−1 under visible light irradiation (λ ≥ 420 nm), which is 3.1 times than that of CuInS2 powder. This work points out a novel method to enhance photocatalytic hydrogen evolution.

Hierarchical porous N-doped carbon-supported PtCu nanoparticles as an efficient catalyst for oxygen reduction reaction

The catalyst of PtCu bimetallic nanoparticles anchored on hierarchical porous N-doped carbon (PtCu/NHPC) is successfully fabricated through a simple pyrolysis synthesis. The high surface area (827 m2 g−1) of N-doped porous carbon (NHPC) can effectively favor the high distribution of PtCu particles on carbon. The high mesopore ratio of NHPC helps to reduce mass transfer resistance. Furthermore, homogeneously distributed nitrogen in carbon can not only uniformly disperse nanoparticles but also optimize catalyst oxygen affinity, significantly improving catalytic efficiency for oxygen reduction reaction. PtCu/NHPC shows excellent electrocatalytic activity with a high half-wave potential (0.915 V vs. RHE) compared with commercial Pt/C (0.864 V) in half-cell test. In the single-cell system, PtCu/NHPC also behaves good performance, and its initial current density is 595 mA cm−2 at 0.85 V. PtCu/NHPC shows better durability (only 6.6% mass activity loss) after 10,000 potential cycles compared to JM Pt/C catalyst (30%). The research provides a simple preparation strategy for improving the oxygen reduction reaction activity and stability of fuel cell platinum-based catalysts.

Experimental study on the absorption enhancement of CO2 by MDEA‐MEA based nanofluids

AbstractNanofluids promote the application of nanotechnology in the mass transfer process, which can effectively reduce mass transfer resistance and increase the gas–liquid mass transfer rate. A bubbling absorption system was used to explore the CO2 absorption performance of methyldiethanolamine (MDEA) and monoethanolamine (MEA) blended nanofluids. TiO2 nanoparticles and sodium polyacrylate (ASAP) surfactant were added to MDEA‐MEA aqueous solutions to prepare nanofluids. The effects of MDEA concentration, MEA concentration, blended amine ratio, and nanoparticle solid content on CO2 capture performance were investigated, respectively. The study found that, compared with single‐component MEA/MDEA solutions, nanofluids have a more significant enhancement in CO2 absorption of blended amines. The increase of MEA concentration in blended amine has a negative effect on the enhanced CO2 absorption of TiO2 nanoparticles. The enhancement factor of MDEA‐MEA nanofluids at each solid content is higher than that of two single‐component nanofluids. The best solid content of TiO2 nanoparticles in the MDEA‐MEA system is 0.6 g/L, while the enhancement factor E in 25% MDEA + 5% MEA nanofluids can reach up to 1.36. Finally, a new empirical formula was proposed to predict the enhancement factor and optimum solid content of TiO2‐MEA/MDEA nanofluids.

Crystallization characteristics and structural analysis of CaO–SiO2-based mold fluxes with different La2O3 contents

To elucidate deterioration mechanism of La2O3 on the crystallization performance of conventional mold fluxes, crystallization characteristics and structure of CaO–SiO2-based mold fluxes with various contents of La2O3 were studied. Results showed that adding 0 wt% to 15 wt% La2O3 increased initial crystallization temperature and critical cooling rate of slags. Crystalline phases changed from Ca4Si2F2O7 to CaLa2(SiO4)2 and Ca4Si2F2O7 with the increase in content of La2O3. Furthermore, crystallization incubation time was shortened gradually. Combined with structural analysis, the main reasons for enhanced crystallization characteristics of mold fluxes with La2O3 were following two factors. First, high-polymerized Q3 units were simplified by O2− released from La2O3 to form low-polymerized units Q2, Q1, and Q0. As a result, NBO/T of slags increased and the degree of polymerization decreased, resulting in the reduction of mass transfer resistance of ions and facilitating crystal nucleation. Second, with an increase in La2O3 content, La3+ exhibited strong attraction to simpler Q0 ([SiO4]4-) units due to its high field strength and large electric charge, which was conducive to the precipitation of rare earth phase. In this study, La3+ together with Ca2+ played charge balance effect and combined with Q0 units to form CaLa2(SiO4)2 phase at high temperature.

Integrated Sn/CNT@N[sbnd]C hierarchical porous gas diffusion electrode by phase inversion for electrocatalytic reduction of CO2

A 3D integrated hierarchical porous N-doped Sn/CNT@NC gas diffusion electrode is proposed via phase inversion to synergistically improve electron-proton-gas transfer and efficiency of CO2 reduction reaction (CO2RR). Hierarchical porous structure is tuned by the carbon nanotube additive during phase inversion, which integrates microporous layer and diffusion layer to decrease mass transfer resistance comparing with the 2D layer structure of commercial carbon paper. XPS results show that Sn/CNT@NC 800 contains pyridinic nitrogen and pyrrolic nitrogen with catalytic activity. EIS and LSV curves show that Sn/CNT@NC 800 is beneficial to reduce mass transfer resistance and increase current density after twice hydrophobic treatments. As a result, Sn/CNT@NC 800 shows higher CO2RR electrocatalytic activity. The reaction rate and Faraday efficiency of CO at 12 mA cm−2 increase by 40.2% and 40.6%, respectively compared with Sn/carbon paper. The reaction rate and Faraday efficiency of formate are also slightly higher than those of Sn/carbon paper.