Interfacial Microenvironment Research Articles

Surface‐Interface Engineering of Electrocatalysts for Two‐Electron Water Oxidation Reaction to Produce H2O2

AbstractElectrochemical two‐electron water oxidation reaction (2e− WOR) driven by renewable energy offers an attractive route to produce H2O2, while the corresponding electrocatalyst still requires further improvement for the activity, selectivity, and the resulting H2O2 yield. Surface‐interface engineering of electrocatalysts has great potential to advance 2e− WOR performance. This review provides a succinct yet comprehensive insight into the functional mechanisms of surface‐interfacial properties affecting 2e− WOR performance on electrocatalyst. The Gibbs free energy theoretical framework related to surface electronic structure and interfacial reactive kinetics mechanism related to electrolyte, electrode–electrolyte interface structure, and interfacial microenvironment properties are firstly discussed. Afterward, various surface‐interface engineering strategies toward high performance electrocatalysts including the regulation of surface electronic structure, the electrode–electrolyte interface structure, and the interfacial microenvironment have been overviewed. Rational manipulations of the above surface‐interfacial engineering strategies are critical to design highly efficient 2e− WOR electrocatalysts, leading to the development of the green H2O2 production.

Rational design of pulse-electrolysis protocols promotes molten-salt electrorefining

Molten-salt electrorefining (MSE) is currently the primary method for purifying many elements, offering promise for the sustainable upcycling of spent metals in the future. However, the conventional constant-current electrolysis protocol inevitably leads to deterioration of the microenvironment near the electrode, leading to reaction runaway and process inefficiency. In this work, we comprehensively studied for the first time the effect of constant- and pulse-electrolysis protocols on environmental evolution in electrode–electrolyte interfaces during the MSE of Ti, using a computer model. The results showed that compared to constant electrolysis, pulse-electrolysis protocols could effectively regulate the interfacial microenvironment and improve the electrorefining efficiency. Furthermore, a correlation between interfacial reconstruction and pulse parameters was established, indicating that the duty ratio was the key factor in inhibiting the deterioration of the interfacial microenvironment. To further verify the simulation results, the real-time morphological evolution of the electrodes during electrolysis was monitored by a novel in situ X-ray computed tomography (CT) technology under pulse-electrolysis protocols. The experimental results indicated that the pulse-electrolysis protocols enhanced the interfacial microenvironment and promoted electrolysis efficiency. Collectively, this work demonstrated that MSE could be effectively advanced by rationally designing the pulse-electrolysis protocols, facilitating its large-scale application in industry.

Enhanced electrocatalytic C[sbnd]H amination of toluene via tailored interfacial microenvironment

Electrocatalytic CH amination of hydrocarbons is a promising avenue for the synthesis of high-value CN compounds. However, efficient activation of CH bonds remains a significant challenge in electrocatalytic CN coupling. Herein, we present a novel strategy to enhance the electrocatalytic conversion of toluene to N-benzylacetamide through a Ritter–type reaction by engineering a hydrophobic electrode–electrolyte interface using polytetrafluoroethylene (PTFE)-coated carbon paper (CP). The hydrophobic CP-based electrode exhibited a superior N-benzylacetamide productivity of 1860.9 mmol m−2h−1 and a substantially higher Faradaic efficiency (FE) of 70.1 % compared to pure CP (41.5 %). Experimental results and density functional theory (DFT) calculations reveal that the PTFE coating promotes toluene adsorption and efficiently lowers the energy barrier for toluene dehydrogenation. Additionally, the hydrophobic interface effectively hinders water adsorption on the electrode, suppressing the competitive water oxidation reaction. This study underscores the crucial role of interfacial engineering in optimizing electrocatalytic CN coupling reactions for the sustainable synthesis of high-value amide compounds.

Phase-Specific Immobilization of Phospholipase D as an Efficient Pickering Emulsion Interfacial Catalyst for Converting Antarctic Krill Oil Phospholipid.

Phosphatidylserine (PS), a rare phospholipid in Antarctic krill oil (AKO) critical for brain development, can be produced from the abundant phosphatidylcholine (PC) using phospholipase D (PLD) in Pickering emulsion interfacial catalysis (PIC) systems. However, the exposure of PLD to organic solvent around the emulsion interface diminished PLD activity, limiting the conversion efficiency of PS. In this study, we proposed a strategy to fabricate a PIC system with high efficiency and stability by immobilizing PLD in a specific phase on the emulsion interface, based on investigating the effect of the interfacial microenvironment on PLD activity. Janus-poly(acrylic acid)/polystyrene (JPP) and Janus-polyethylenimine/octadecane (JPO) particles were fabricated as carriers to realize the specific-phase immobilization of PLD. The highest activity was observed when PLD was immobilized on the hydrophilic side of JPP (PLD@JPP(W)), 1.9-fold that of free PLD. The catalytic efficiency of PLD@JPP(W) was 1.7-fold that of free PLD, confirmed by the kcat/Km value enhancement. Immobilization on the hydrophilic side also enhanced the thermal stability of PLD. The half-lives of PLD were extended from 4 to 36 h at 40 °C and from 6 to 28 days at 4 °C. Importantly, PLD@JPP(W) showed excellent catalytic efficiency as a PIC system, achieving a PS productivity of 93% within a short time of 2 h at an enzyme dosage of 0.05 mg. PLD@JPP(W) exhibited a 3.6 times higher yield than free PLD in the production of PS from PC rich in Antarctic krill oil. The strategy in this work could also be applied to other lipases, providing a promising method for the efficient conversion of functional lipids.

Fluorine-Doped Carbon Support Enables Superfast Oxygen Reduction Kinetics by Breaking the Scaling Relationship.

It is well-established that Pt-based catalysts suffer from the unfavorable linear scaling relationship (LSR) between *OOH and *OH (ΔG(*OOH)=ΔG(*OH)+3.2±0.2 eV) for the oxygen reduction reaction (ORR), resulting in a great challenge to significantly reduced ORR overpotentials. Herein, we propose a universal and feasible strategy of fluorine-doped carbon supports, which optimize interfacial microenvironment of Pt-based catalysts and thus significantly enhance their reactive kinetics. The introduction of C-F bonds not only weakens the *OH binding energy, but also stabilizes the *OOH intermediate, resulting in a break of LSR. Furthermore, fluorine-doped carbon constructs a local super-hydrophobic interface that facilitates the diffusion of H2O and the mass transfer of O2. Electrochemical tests show that the F-doped carbon-supported Pt catalysts exhibit over 2-fold higher mass activities than those without F modification. More importantly, those catalysts also demonstrate excellent stability in both rotating disk electrode (RDE) and membrane electrode assembly (MEA) tests. This study not only validates the feasibility of tuning the electrocatalytic microenvironment to improve mass transport and to break the scaling relationship, but also provides a universal catalyst design paradigm for other gas-involving electrocatalytic reactions.

Fluorine‐Doped Carbon Support Enables Superfast Oxygen Reduction Kinetics by Breaking the Scaling Relationship

AbstractIt is well‐established that Pt‐based catalysts suffer from the unfavorable linear scaling relationship (LSR) between *OOH and *OH (ΔG(*OOH)=ΔG(*OH)+3.2±0.2 eV) for the oxygen reduction reaction (ORR), resulting in a great challenge to significantly reduced ORR overpotentials. Herein, we propose a universal and feasible strategy of fluorine‐doped carbon supports, which optimize interfacial microenvironment of Pt‐based catalysts and thus significantly enhance their reactive kinetics. The introduction of C−F bonds not only weakens the *OH binding energy, but also stabilizes the *OOH intermediate, resulting in a break of LSR. Furthermore, fluorine‐doped carbon constructs a local super‐hydrophobic interface that facilitates the diffusion of H2O and the mass transfer of O2. Electrochemical tests show that the F‐doped carbon‐supported Pt catalysts exhibit over 2‐fold higher mass activities than those without F modification. More importantly, those catalysts also demonstrate excellent stability in both rotating disk electrode (RDE) and membrane electrode assembly (MEA) tests. This study not only validates the feasibility of tuning the electrocatalytic microenvironment to improve mass transport and to break the scaling relationship, but also provides a universal catalyst design paradigm for other gas‐involving electrocatalytic reactions.

Facilitating photocatalytic CO2 methanation via synergetic feed of photon-induced carriers and reactants over S-scheme BiVO4@TiO2 nanograss/needle arrays

Herein, a unique structure BiVO4@TiO2 nanograss/needle arrays S-scheme heterojunction photocatalyst for CO2 photoreduction reaction was created. The photocatalyst can drive electrons to the reactive spots spontaneously and continuously, which effectively tackles the problem of severe recombination and disordered migration of photogenerated carriers. Theoretical calculations and experimental results demonstrate that adding BMIM-BF4 ionic liquid to generate BMIM-*CO2 intermediate promotes CO2 activation and enrichment of reactants concentration around the catalytic sites. Benefiting from the sufficient electron supply of catalytic sites and reinforced reactants supply in the interfacial microenvironment, the BiVO4@TiO2 photocatalyst shows high selectivity and activity of CO2-to-CH4 conversion. The CH4 selectivity increased to 57.3 % (132.7 μmol m-2h−1) and the methanation activity was increased by 8.6 times in the 5.0 % BMIM-BF4 aqueous solution. Significantly, the BiVO4@TiO2 NNAs catalyst obtains a solar-to-fuels energy efficiency of ∼ 0.46 ‰ under ultraviolet-enhanced light sources without any sacrificial agent or co-catalyst. This work displays the relationship between reaction process factors (electron supply, CO2 molecule, and proton supply) and CO2 photoreduction activity and selectivity, giving new insight into achieving efficient CO2 photoreduction conversion.

Polyelectrolyte Additive‐Modulated Interfacial Microenvironment Boosting CO2 Electrolysis in Acid

Acidic CO2 electrolysis offers a promising strategy to achieve high carbon utilization and high energy efficiency. However, challenges remain in suppressing the competitive hydrogen evolution reaction (HER) and improving product selectivity. High concentrations of potassium ions (K+) can suppress HER and accelerate CO2 reduction, but they still inevitably suffer from salt precipitation problems. In this study, we demonstrate that the sulfonate‐based polyelectrolyte, polystyrene sulfonate (PSS), enables to reconstruct the electrode‐electrolyte interface to significantly enhance the acidic CO2 electrolysis. Mechanistic studies reveal that PSS induces high local K+ concentrations through electrostatic interaction between PSS anions and K+. In situ spectroscopy reveals that PSS reshapes the interfacial hydrogen–bond (H–bond) network, which is attributed to the H–bonds between PSS anions and hydrated proton as well as the steric hindrance of the additive molecules. This greatly weakens proton transfer kinetics and leads to the suppression of undesirable HER. As a result, a Faradaic efficiency of 93.9% for CO can be achieved at 250 mA cm–2, simultaneous with a high single‐pass carbon efficiency of 72.2% on commercial Ag catalysts in acid. This study highlights the important role of the electrode‐electrolyte interface induced by polyelectrolyte additives in promoting electrocatalytic reactions.

Stabilized Cuδ+-OH species on in situ reconstructed Cu nanoparticles for CO2-to-C2H4 conversion in neutral media

Achieving large-scale electrochemical CO2 reduction to multicarbon products with high selectivity using membrane electrode assembly (MEA) electrolyzers in neutral electrolyte is promising for carbon neutrality. However, the unsatisfactory multicarbon products selectivity and unclear reaction mechanisms in an MEA have hindered its further development. Here, we report a strategy that manipulates the interfacial microenvironment of Cu nanoparticles in an MEA to suppress hydrogen evolution reaction and enhance C2H4 conversion. In situ multimodal characterizations consistently reveal well-stabilized Cuδ+-OH species as active sites during MEA testing. The OH radicals generated in situ from water create a locally oxidative microenvironment on the copper surface, stabilizing the Cuδ+ species and leading to an irreversible and asynchronous change in morphology and valence, yielding high-curvature nanowhiskers. Consequently, we deliver a selective C2H4 production with a Faradaic efficiency of 55.6% ± 2.8 at 316 mA cm−2 in neutral media.

Synergistic Effects of the Electric Field Induced by Imidazolium Rotation and Hydrogen Bonding in Electrocatalysis of CO2.

The roles of the ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), and water in controlling the mechanism, energetics, and electrocatalytic activity of CO2 reduction to CO on silver in nonaqueous electrolytes were investigated. The first electron transfer occurs to CO2 at reduced overpotentials when it is trapped between the planes of the [EMIM]+ ring and the electrode surface due to cation reorientation as determined from voltammetry, in situ surface-enhanced Raman spectroscopy, and density functional theory calculations. Within this interface, water up to 0.5 M does not induce significant Faradaic activity, opposing the notion of it being a free proton source. Instead, water acts as a hydrogen bond donor, and the proton is sourced from [EMIM]+. Furthermore, this study demonstrates that alcohols with varying acidities tune the hydrogen bonding network in the interfacial microenvironment to lower the energetics required for CO2 reduction. The hydrogen bonding suppresses the formation of inactive carboxylate species, thus preserving the catalytic activity of [EMIM]+. The ability to tune the hydrogen bonding network opens new avenues for advancing IL-mediated electrocatalytic reactions in nonaqueous electrolytes.

Tailoring the interfacial microenvironment by electrolyte engineering boosts bicarbonate electrolysis

AbstractBicarbonate electrolysis, as a carbon utilization technology with high efficiency and potential for industrial applications, provides a promising pathway for CO2 emission reduction. However, how to inhibit serious hydrogen evolution reaction (HER) and increase the relatively low CO2 concentration at the electrode‐electrolyte interfacial is challenging. Here, we introduce three typical aminopolycarboxylic acids (APCAs) with different amounts of carboxylic acid roots into 3 M KHCO3 to enhance the Faradaic efficiency of CO (FECO) from 51.2% to 68.0% at 100 mA cm−2. Spectroscopic characterization confirms that the role of APCAs in confining the activity of water dissociation and improving the availability of CO2. The strategy adopted in this work that introducing APCAs into the electrolyte to balance the content of CO2 and H2O for improving the electrocatalytic performance, can serve as a reference for other electrocatalytic systems.

Tip-intensified engineering of interfacial microenvironment toward pH-universal hydrogen evolution reaction

Engineering a robust non-platinum electrode toward hydrogen evolution reaction (HER) is important for water electrolysis. Here we develop a nanotip-structured electrode through a solution phase etching procedure. Based on the experimental and finite element simulation, the results show that the nanotip-structured design of electrodes cannot only lower the adhesion force of bubbles, but also induce a local-concentrated electric field that can promote the formation of Marangoni effect, and K+ concentrated and local acid-like microenvironment, consequently facilitating the detachment of bubbles and the HER kinetics. The electrochemical measurements and density function theory (DFT) calculation indicate that the constructed electrode exhibits a low H* binding energy and an outstanding HER performance that outperforms the commercial Pt/C in pH-universal medium. Overall, this work provides a feasible strategy for electrode design with a pH-universal feasibility by precisely constructing electrode interfaces.

Anionic Surfactant-Modulated Electrode-Electrolyte Interface Promotes H2O2 Electrosynthesis.

Conventional strategies for highly selective and active hydrogen peroxide (H2O2) electrosynthesis primarily focus on catalyst design. Electrocatalytic reactions take place at the electrified electrode-electrolyte interface. Well-designed electrolytes, when combined with commercial catalysts, can be directly applied to high-efficiency H2O2 electrosynthesis. However, the role of electrolyte components is equally crucial but is significantly under-researched. In this study, anionic surfactant n-tetradecylphosphonic acid (TDPA) and its analogs are used as electrolyte additives to enhance the selectivity of the two-electron oxygen reduction reaction. Mechanistic studies reveal that TDPA assembled over the electrode-electrolyte interface modulates the electrical double-layer structure, which repels interfacial water and weakens the hydrogen-bond network for proton transfer. Additionally, the hydrophilic phosphonate moiety affects the coordination of water molecules in the solvation shell, thereby directly influencing the proton-coupled kinetics at the interface. The TDPA-containing catalytic system achieves a Faradaic efficiency of H2O2 production close to 100% at a current density of 200mA cm-2 using commercial carbon black catalysts. This research provides a simple strategy to enhance H2O2 electrosynthesis by adjusting the interfacial microenvironment through electrolyte design.

Anionic Surfactant-Tailored Interfacial Microenvironment for Boosting Electrochemical CO2 Reduction.

Both the catalyst and electrolyte deeply impact the performance of the carbon dioxide reduction reaction (CO2RR). It remains a challenge to design the electrolyte compositions for promoting the CO2RR. Here, typical anionic surfactants, dodecylphosphonic acid (DDPA) and its analogues, are employed as electrolyte additives to tune the catalysis interface where the CO2RR occurs. Surprisingly, the anionic surfactant-tailored interfacial microenvironment enables a set of typical commercial catalysts for the CO2RR to deliver a significantly enhanced selectivity of carbon products in both neutral and acidic electrolytes. Mechanistic studies disclose that the DDPA addition restructures the interfacial hydrogen-bond environment via increasing the weak H-bonded water, thus promoting the CO2 protonation to CO. Specifically, in an H-type cell, the Faradaic efficiency of CO increases from 70 to 98% at -1.0 V versus the reversible hydrogen electrode. Furthermore, in a flow cell, the DDPA-containing electrolyte maintains over 90% FECO from 50-400 mA cm-2. Additionally, this electrolyte modulation strategy can be extended to acidic CO2RR with a pH of 1.5-3.5.

Efficient Electrosynthesis of Urea over Single-Atom Alloy with Electronic Metal Support Interaction.

Urea electrosynthesis from carbon dioxide (CO2) and nitrate (NO3 -) is an alternative approach to traditional energy-intensive urea synthesis technology. Herein, we report a CuAu single-atom alloy (SAA) with electronic metal support interaction (EMSI), achieving a high urea yield rate of 813.6 μg h-1 mgcat -1 at -0.94 V versus reversible hydrogen electrode (vs. RHE) and a Faradaic efficiency (FE) of 45.2 % at -0.74 V vs. RHE. In situ experiments and theoretical calculations demonstrated that single-atom Cu sites modulate the adsorption behavior of intermediate species. Bimetallic sites synergistically accelerate C-N bond formation through spontaneous coupling of *CO and *NO to form *ONCO as key intermediates. More importantly, electronic metal support interaction between CuAu SAA and CeO2 carrier further modulates electron structure and interfacial microenvironment, endowing electrocatalysts with superior activity and durability. This work constructs SAA electrocatalysts with EMSI effect to tailor C-N coupling at the atomic level, which can provide guidance for the development of C-N coupling systems.

Efficient Electrosynthesis of Urea over Single‐Atom Alloy with Electronic Metal Support Interaction

AbstractUrea electrosynthesis from carbon dioxide (CO2) and nitrate (NO3−) is an alternative approach to traditional energy‐intensive urea synthesis technology. Herein, we report a CuAu single‐atom alloy (SAA) with electronic metal support interaction (EMSI), achieving a high urea yield rate of 813.6 μg h−1 mgcat−1 at −0.94 V versus reversible hydrogen electrode (vs. RHE) and a Faradaic efficiency (FE) of 45.2 % at −0.74 V vs. RHE. In situ experiments and theoretical calculations demonstrated that single‐atom Cu sites modulate the adsorption behavior of intermediate species. Bimetallic sites synergistically accelerate C−N bond formation through spontaneous coupling of *CO and *NO to form *ONCO as key intermediates. More importantly, electronic metal support interaction between CuAu SAA and CeO2 carrier further modulates electron structure and interfacial microenvironment, endowing electrocatalysts with superior activity and durability. This work constructs SAA electrocatalysts with EMSI effect to tailor C−N coupling at the atomic level, which can provide guidance for the development of C−N coupling systems.

Steering sulfur reduction kinetics of lithium-sulfur batteries by interfacial microenvironment modulation

Catalytic conversion of lithium polysulfides (LiPSs) is considered as an effective avenue to suppress the shuttle effect of lithium-sulfur (Li-S) batteries, for which the interfacial microenvironment constructed by the interaction between electrocatalysts and LiPSs plays a pivotal role in modulating the sulfur reduction kinetics. However, most of previous reports mainly focused on modulating the band structure of electrocatalysts or LiPSs alone to enhance the catalytic activity rather than considering the interfacial microenvironment as a whole. Herein, we propose a binary descriptor composed of the energy difference between d-band of electrocatalysts and p-band of LiPSs (ΔεM-S) and the antibonding filling degree (εABF), which capture the energy band contributions from both electrocatalysts and LiPSs, to reveal the influence of interfacial microenvironment on sulfur reduction kinetics. Among different designed electrocatalysts, NiO presents a moderate LiPSs anchoring capacity and rapid electron transfer kinetics owing to the optimal ΔεM-S and decreased εABF after interacting with LiPSs, which lead to a robust interfacial microenvironment and thus guarantee a continuous catalytic conversion of LiPSs in the long-term cycling. Such a fundamental understanding of catalytic activity toward LiPSs from the viewpoint of interfacial microenvironment provides an alternative avenue for designing highly efficient electrocatalysts for Li-S batteries.

Superior activity and durability of Co3Mo correlated with interfacial microenvironment for hydrogen evolution

Interfacial microenvironment is critical for the effective matching of catalyst and electrolyte. In this work, interfacial microenvironment is modulated to simultaneously improve catalytic activity and durability of Co3Mo. The dissolution of Mo atoms in Co3Mo during HER produces MoO42-, which can be further dimerized into Mo2O72- at high overpotential. Adsorption of Mo2O72- at the catalyst interface modulates the electronic structure of the surface active atoms, thereby reducing the Gibbs free energy required for HER. An optimal ratio of Mo2O72- with a critical MoO42- concentration of ∼13.4 mM in the electrolyte can make a positive contribution to catalytic activity, which is evidenced by ultralow overpotential of 78 mV at current density of 100 mA·cm−2. Meanwhile, almost no voltage increase is detected after 325 h at a current density of 0.5 A·cm−2 in an anion-exchange membrane electrolyzer. This investigation provides a strategic and scientific route for industrial electrolyzer based on Mo-based alloys.

Experimental and Theoretical Investigation of Interfacial Engineering in Fe2O3/NiFe2O4 Heterostructures toward the Cycloaddition of CO2 with Styrene Oxide.

The chemical fixation of CO2 into epoxides for the synthesis of cyclic carbonates is an appealing solution to both reduce global CO2 emission and produce fine chemicals, but it is still a prime challenge to develop a low-cost, earth-abundant, yet efficient solid catalyst. Herein, Fe2O3/NiFe2O4 heterostructures are facilely constructed for the highly efficient cycloaddition of CO2 with styrene oxide (SO) to produce styrene carbonate (SC). Both experimental findings and density functional theory (DFT) calculations substantiate the prominent electron transfer and charge redistribution within the heterointerfaces between the biphasic components, which induce a unique interfacial microenvironment that can facilitate the adsorption and activation of SO. This endows the biphasic catalyst with a substantially higher reactivity than the individual components. This study sheds new insights into the establishment of heterostructured catalysts consisting of transitional metal oxides for the high-efficiency production of SC from the cycloaddition of CO2 with SO.

Surfactant Directionally Assembled at the Electrode-Electrolyte Interface for Facilitating Electrocatalytic Aldehyde Hydrogenation.

Electrocatalytic hydrogenation of unsaturated aldehydes to unsaturated alcohols is a promising alternative to conventional thermal processes. Both the catalyst and electrolyte deeply impact the performance. Designing the electrode-electrolyte interface remains challenging due to its compositional and structural complexity. Here, we employ the electrocatalytic hydrogenation of 5-hydroxymethylfurfural (HMF) as a reaction model. The typical cationic surfactant, cetyltrimethylammonium bromide (CTAB), and its analogs are employed as electrolyte additives to tune the interfacial microenvironment, delivering high-efficiency hydrogenation of HMF and inhibition of the hydrogen evolution reaction (HER). The surfactants experience a conformational transformation from stochastic distribution to directional assembly under applied potential. This oriented arrangement hampers the transfer of water molecules to the interface and promotes the enrichment of reactants. In addition, near 100 % 2,5-bis(hydroxymethyl)furan (BHMF) selectivity is achieved, and the faradaic efficiency (FE) of the BHMF is improved from 61 % to 74 % at -100 mA cm-2. Notably, the microenvironmental modulation strategy applies to a range of electrocatalytic hydrogenation reactions involving aldehyde substrates. This work paves the way for engineering advanced electrode-electrolyte interfaces and boosting unsaturated alcohol electrosynthesis efficiency.