The atomic interface effect of single atom catalysts for electrochemical hydrogen peroxide production

Producing hydrogen peroxide(H_(2)O_(2))through an electrochemical oxygen reduction reaction(ORR)is a safe,green strategy and a promising alternative to traditional energy-intensive anthraquinone processes.Air and renewable power could be utilized for onsite and decentralized H_(2)O_(2)production,demonstrating significant application potential.Currently,single atom catalysts(SACs)have demonstrated significant advantages in the catalytic production of H_(2)O_(2)in 2e−ORR.However,the selectivity of SACs in ORR once puzzled researchers.This article reviews the research on the development and achievements of H_(2)O_(2)production by SACs catalysis in recent years.Especially,the structure-performance relationship is a guide to designing new SACs.Combining advanced characterization techniques and theoretical calculation methods,researchers have a clearer and more thorough understanding of the impact of the atomic interface of SACs on ORR catalytic performance.The coordination moiety formed between the active metal center atom and the support seriously determines the selectivity of SACs,mainly manifested in the adsorption of*OOH intermediates.Particularly,the atomic interface of metal atoms together with O/N co-coordination exhibit high selectivity and mass activity,and heteroatoms or functional groups on carbon supports present synergistic effects to promote the production of H_(2)O_(2)in 2e−ORR.Fine and accurate regulation of the atomic interface of SACs directly affects the 2e−ORR performance of the catalysts.Therefore,it is important to deeply understand the atomic interface of SACs and contribute to the development of novel catalysts.

Enhancing photocatalytic hydrogen peroxide production of Tibased metal-organic frameworks:The leading role of facet engineering

Rational construction of the facet engineering over metal-organic frameworks is of significant interest for enhancing photocatalytic performance,yet the role of modulator except regulating facet is largely ignored.Herein,facet engineering of NH_(2)-MIL125(aMIL)was achieved through the facile one-pot method by controlling the concentration of acetic acid modulator.The probable domino effects induced with the detectable modulator were extensively investigated,evidencing the multi-position in one mode contained powder X-Ray diffraction(PXRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),and X-ray absorption spectroscopy(XAS),etc.Meanwhile,correlation among the{111}facets engineering,the degree of structural defects,and the performance of photocatalytic hydrogen peroxide(H_(2)O_(2))production was studied in detail,revealing that facet and defect engineering respectively play positive and relatively negative roles in the photocatalytic oxygen reduction reaction(ORR)with a volcano-type trend.aMIL-3 photocatalyst could deliver H_(2)O_(2) production rate of 925.8μmol·h^(−1)·g^(−1)(2.03-fold of aMIL)under visible-light irradiation and a quantum yield of 1.08%at 420 nm.

Aqueous Synthesis of Covalent Organic Frameworks as Photocatalysts for Hydrogen Peroxide Production

Covalent organic frameworks(COFs)are crystalline porous polymers with designable structures and properties.Their crystallization typically relies on trialand-error experimentation involving harsh conditions,including organic solvents,presenting significant obstacles for rational design and large-scale production.Herein,we present a liquid crystal-directed synthesis methodology and its implementation for up to gram-scale production of highly crystalline COFs in water and air.It is compatible with monomers of different structures,shape,size,length of side chains,and electron-donating,electron-accepting,and heterocyclic substitutions near reactive sites.Seventeen types of donor-acceptor two-dimensional COFs including four types of new ones and a three-dimensional COF with a yield of up to 94%were demonstrated,showing great generality of the method.The as-synthesized donor-acceptor COFs are organic semiconductors and contain macropores besides intrinsic mesopores which make them attractive catalysts.The production of H_(2)O_(2)under visible light in water was studied and the structure-property relationships were revealed.The production rate reached 4347μmol h^(−1)gcat^(−1),which is about 467%better than that of the benchmark photocatalyst g-C_(3)N_(4).This study will inspire the mild synthesis and scale-up of a wide spectrum of COFs and organic semiconductors as efficient catalysts,promote their structure-property investigation,and boost their applications.

High-rate electrochemical H_(2)O_(2) production over multimetallic atom catalysts under acidic–neutral conditions

Hydrogen peroxide(H_(2)O_(2))production by the electrochemical 2-electron oxygen reduction reaction(2e−ORR)is a promising alternative to the energy-intensive anthraquinone process,and single-atom electrocatalysts show the unique capability of high selectivity toward 2e−ORR against the 4e−one.The extremely low surface density of the single-atom sites and the inflexibility in manipulating their geometric/electronic configurations,however,compromise the H_(2)O_(2) yield and impede further performance enhancement.Herein,we construct a family of multiatom catalysts(MACs),on which two or three single atoms are closely coordinated to form high-density active sites that are versatile in their atomic configurations for optimal adsorption of essential*OOH species.Among them,the Cox–Ni MAC presents excellent electrocatalytic performance for 2e−ORR,in terms of its exceptionally high H_(2)O_(2) yield in acidic electrolytes(28.96 mol L^(−1) gcat.^(−1) h^(−1))and high selectivity under acidic to neutral conditions in a wide potential region(>80%,0–0.7 V).Operando X-ray absorption and density functional theory analyses jointly unveil its unique trimetallic Co2NiN8 configuration,which efficiently induces an appropriate Ni–d orbital filling and modulates the*OOH adsorption,together boosting the electrocatalytic 2e−ORR capability.This work thus provides a new MAC strategy for tuning the geometric/electronic structure of active sites for 2e−ORR and other potential electrochemical processes.

Efficient production of hydrogen peroxide in microbial reverse-electrodialysis cells coupled with thermolytic solutions

H_(2)O_(2) was produced at an appreciable rate in microbial reverse-electrodialysis cells(MRCs)coupled with thermolytic solutions,which can simultaneously capture waste heat as electrical energy.To determine the optimal cathode and membrane stack configurations for H_(2)O_(2) production,different catalysts,catalyst loadings and numbers of membrane cell pairs were tested.Carbon black(CB)outperformed activated carbon(AC)for H_(2)O_(2) production,although AC showed higher catalytic activity for oxygen reduction.The optimum CB loading was 10 mg/cm^(2) in terms of both the H_(2)O_(2) production rate and power production.The optimum number of cell pairs was determined to be three based on a tradeoff between H_(2)O_(2) production and capital costs.A H_(2)O_(2) production rate as high as 0.99±0.10 mmol/(L·h)was achieved with 10 mg/cm^(2) CB loading and 3 cell pairs,where the H_(2)O_(2) recovery efficiency was 52±2%and the maximum power density was 780±37 mW/m^(2).Increasing the number of cell pairs to five resulted in an increase in maximum power density(980±21 mW/m^(2))but showed limited effects on H_(2)O_(2) production.These results indicated that MRCs can be an efficient method for sustainable H_(2)O_(2) production.

Fullerene-derived boron-doped defective nanocarbon for highly selective H_(2)O_(2) electrosynthesis

Electrochemical production of hydrogen peroxide(H_(2)O_(2))via the two-electron(2e-)pathway of oxygen reduction reaction(ORR)supplies an auspicious alternative to the current industrial anthraquinone process.Nonetheless,it still lacks efficient electrocatalysts to achieve high ORR activity together with 2e-selectivity simultaneously.Herein,a boron-doped defective nanocarbon(B-DC)electrocatalyst is synthesized by using fullerene frameworks as the precursor and boric oxide as the boron source.The obtained B-DC materials have a hierarchical porous structure,befitting boron dopants,and abundant topological pentagon defects,exhibiting a high ORR onset potential of 0.78 V and a dominated 2e-selectivity(over 95%).Remarkably,when B-DC electrocatalyst is employed in a real device,it achieves a high H_(2)O_(2) yield rate(247 mg·L^(-1)·h^(-1)),quantitative Faraday efficiency(~100%),and ultrafast organic pollutant degradation rate.The theoretical calculation reveals that the synergistic effect of topological pentagon defects and the incorporation of boron dopants promote the activation of the O_(2) molecule and facilitates the desorption of oxygen intermediate.This finding will be very helpful for the comprehension of the synergistic effect of topological defects and heteroatom dopants for boosting the electrocatalytic performance of nanocarbon toward H_(2)O_(2) production.

Surface Oxidation of Single-walled-carbon-nanotubes with Enhanced Oxygen Electroreduction Activity and Selectivity

Electrochemical oxygen reduction reaction(ORR) with 2-electron process is an alternative for decentralized H_(2)O_(2) production, but it remains high challenging to develop highly active and selective catalysts for this process. In this work, we present a selective and efficient nonprecious electrocatalyst, prepared through an easily scalable mild oxidation of single-walled carbon nanotubes(SWNTs) with different oxidative acids including sulfur acid, nitride acid and mixed sulfuric/nitric acids, respectively. The high-degree oxidized SWNTs treated by mixed acids exhibit the highest activity and selectivity of electroreduction of oxygen to synthesize H_(2)O_(2) at low overpotential in alkaline and neutral media. Spectroscopic characterizations suggested that the C–O is vital for catalyzing 2-electron ORR, providing an insightful understanding of defected carbon surface as the active catalytic sites for 2-electron ORR.