Phosphorous and selenium tuning Co-based non-precious catalysts for electrosynthesis of H_(2)O_(2)in acidic media

Electrosynthesis of hydrogen peroxide(H2O2)is an on-site method that enables independent distribution applications in many fields due to its small-scale and sustainable features.The crucial point remains developing highly active,selective and cost-effective electrocatalysts.The electrosynthesis of H2O2 in acidic media is more practical owing to its stability and no need for further purification.We herein report a phosphorus and selenium tuning Co-based non-precious catalyst(CoPSe)toward two-electron oxygen reduction reaction(2e–ORR)to produce H2O2 in acidic media.The starting point of using both P and Se is finding a balance between strong ORR activity of CoSe and weak activity of CoP.The results demonstrated that the CoPSe catalyst exhibited the optimized 2e–ORR activity compared with CoP and CoSe.It disclosed an onset potential of 0.68 V and the H2O2 selectivity 76%-85%in a wide potential range(0–0.5 V).Notably,the CoPSe catalyst overcomes a significant challenge of a narrow-range selectivity for transitionmetal based 2e–ORR catalysts.Finally,combining with electro-Fenton reaction,an on-site system was constructed for efficient degradation of organic pollutants.This work provides a promising non-precious Co-based electrocatalyst for the electrosynthesis of H2O2 in acidic media.

Ultrafine Co nanoparticles confined in nitrogen-doped carbon toward two-electron oxygen reduction reaction for H_(2)O_(2) electrosynthesis in acidic media

Electrocatalytic production of hydrogen peroxide(H_(2)O_(2))by two-electron oxygen reduction reaction(2e^(-)ORR)under acidic condition has been considered to have great application value.Co nanoparticles(CoNPs)coupled with N-doped carbon are a class of potential electrocatalysts.The effective strategies to further enhance their performances are to improve the active sites and stability.Herein,the material containing ultrafine CoNPs confined in a nitrogen-doped carbon matrix(NC@CoNPs)was synthesized by pyrolyzing corresponding precursors,which was obtained through regulating the topological structure of ZIF-67/ZIF-8 with dopamine(DA).The DA self-polymerization process induced the formation of CoNPs with smaller sizes and formed polydopamine film decreased the detachment of CoNPs from the catalyst.High density of Co-N_(x) active sites and defective sites could be identified on NC@CoNPs,leading to high activity and H_(2)O_(2) selectivity,with an onset potential of 0.57 V(vs.RHE)and∼90%selectivity in a wide potential range.An on-site electrochemical removal of organic pollutant was achieved rapidly through an electro-Fenton process,demonstrating its great promise for on-site water treatment application.

基于混合电子/离子导体的无膜可穿戴汗液电解质传感器

利用可穿戴传感器对汗液电解质进行无创的实时监测可获得大量与健康相关的生理学信息.目前,可穿戴汗液传感器其电解质传感单元主要是基于固态离子选择电极(SC-ISEs).SC-ISEs包含2个功能传感层,即用于离子识别的离子选择性膜层(ISM)和信号转换的离子-电子转导层.然而,两层之间的水层效应、ISM层离子载体的生物毒性以及昂贵的成本导致SC-ISEs难以实际应用于可穿戴传感领域.本质上,这些挑战都源于ISM.基于此,本文提出了基于钨青铜混合电子/离子导体的无膜(ISM-free)离子传感器.该材料作为双功能传感层,无需传统的ISM,通过晶格实现离子识别,同时W^(6+/5+)氧化还原中心实现离子-电子的转导.相比于传统的离子载体,钨青铜表现出更为优异的性能.基于钨青铜构建的可穿戴离子传感器,实现了人体汗液NH_(4)^(+)和pH的监测.该工作提出了无膜固态离子传感的概念,强调了开发下一代无ISM可穿戴离子传感器的重要性.

Electrochemical probing into the active sites of graphitic-layer encapsulated iron oxygen reduction reaction electrocatalysts

The graphitic-layer encapsulated iron-containing nanoparticles(G@Fe) have been proposed as a potential type of active and stable non-precious metal electrocatalysts(NPMCs) for the oxygen reduction reaction(ORR). However, the contribution of the encapsulated components to the ORR activity is still unclear compared with the well-recognized surface coordinated FeN_x/C structure. Using the strong complexing effect of the iron component with anions, cyanide(CN^-) in alkaline and thiocyanate(SCN^-) in acidic media, the metal containing active sites are electrochemically probed. Three representative catalysts are chosen for a comparison including the as-prepared encapsulated G@Fe, commercial Fe/N/C catalyst with iron–nitrogen coordinated surface functionalities and molecular iron phthalocyanine(Fe Pc) containing well-defined structures and compositions. It was found that all samples showed significant shifts of half-wave potentials indicating that surface Fe coordinated sites in all cases. The G@Fe catalyst showed the weakest poisoning effect(the lowest shifts of half-wave potential) compared to the Fe/N/C and Fe Pc catalysts in both electrolytes. These results could be explained that the encapsulated iron components influence the FeN_x/C and/or N_xC surface functionality.