One-pot pyrolysis synthesis of highly active Ru/RuOx nanoclusters for water splitting

Using simple methods to obtain efficient catalysts has been a long-standing goal for researchers.In this work,the employment of a one-pot pyrolysis reaction to achieve molecular confinement,has led to the preparation of ruthenium(Ru)-based nanoclusters in a carbon matrix.A unique feature of the synthetic approach employed is that solvent and substrates were calcined together.As solvent evaporates,during calcination,the substrates form a dense solid which has the effect of limiting the aggregation of Ru centers during the carbonization process.The catalyst prepared in this simple manner showed an impressively high activity with respect to the hydrogen/oxygen evolution reaction(HER/OER).The Ru nanoclusters(Ru NCs),as the hydrogen evolution reaction(HER)catalysts,require ultralow overpotentials of 5 mV and 5.1 mV at-10 mA·cm^(-2) in 1.0 M KOH,and 0.5 M H_(2)SO_(4),respectively.Furthermore,the catalyst prepared by the one-pot method has higher crystallinity,a higher Ru content and an ultrafine cluster size,which contributes to its exceptional electrochemical performance.Meanwhile,the RuO_(x) nanoclusters(RuO_(x) NCs),obtained by oxidizing the aforementioned Ru NCs,exhibited good oxygen evolution reaction(OER)performance with an overpotential of 266 mV at 10 mA·cm^(-2).When applied to overall water splitting,Ru/RuO_(x) nanoclusters as the cathode and anode catalysts can reach 10 mA·cm^(-2) at cell voltages of only 1.49 V in 1 M KOH.

Interatomic electron transfer promotes electroreduction CO_(2)-to-CO efficiency over a CuZn diatomic site

Diatomic site catalysts(DACs)with two adjacent atomic metal species can provide synergistic interactions and more sophisticated functionalities to break the bottleneck of intrinsic drawbacks of single atom catalysts(SACs).Herein,we have designed a CuZn diatomic site(CuZn-DAS)electrocatalyst with unique coordination structure(CuN_(4)-ZnN_(4))by anchoring and ordering the spatial distance between the metal precursors on the carbon nitride(C_(3)N_(4))derived N-doped carbon(NC)substrate.The CuZn-DAS/NC shows high activity and selectivity for electroreduction CO_(2)into CO.The Faradaic efficiency for CO of CuZn-DAS/NC(98.4%)is higher than that of Cu single atomic site on NC(Cu-SAS/NC)(36.4%)and Zn single atomic site on NC(Zn-SAS/NC)(66.8%)at-0.6 V versus reversible hydrogen electrode(vs.RHE).In situ characterizations reveal that the CuZn-DAS is more favorable for the formation and adsorption of^(*)COOH than those of the electrocatalysts with single atomic site.Theorical calculations show that the charge redistribution of Zn site in CuZn-DAS/NC caused by the considerable electron transfers from Zn atoms to the adjacent Cu atoms can reduce the adsorption energy barriers for^(*)COOH and^(*)CO production,improving the activity and CO selectivity.

原位界面工程构建二元过渡金属碳化物异质结构及其高效全解水性能研究

调控催化剂表面的化学键来平衡表面水分子的吸附和分解对于碱性溶液中水分解至关重要.本研究提出一种通过原位界面工程来设计与合成表面具有丰富的Ni-W金属键的Ni2W4C-W3C Janus异质结构的简便策略.预先将金属离子均匀分散在纳米纤维中,在碳化过程中,以电纺纤维为反应器,金属盐首先被还原成Ni和W3C.在持续分解的过程中,Ni原子原位插入W3C晶体中形成新的Ni2W4C相,得到Ni2W4C-W3C Janus异质结构.这使得W3C中原本惰性的W原子成为Ni2W4C中的活性位点.Ni2W4C-W3C/碳纳米纤维可以直接作为电极材料,其在碱性电解液中析氢活性达到10 m A/cm^2的电流密度需要63 m V过电位,析氧活性达到30 m A/cm^2的电流密度需要270 m V的过电位.若同时用作阴极和阳极进行全解水性能研究,其电池电压分别需要1.55和1.87 V就达到10和100 m A/cm^2.密度泛函理论结果表明,Ni与W之间的强相互作用增强了W原子的局域电子态.Ni2W4C为H-OH键的裂解提供了活性位点,W3C促进了Hads中间体与H2分子的结合.原位电化学拉曼光谱的结果表明该材料对水分子和羟基具有很强的吸收能力,W原子是真正的反应活性位点.该方法为构建高效电解水催化材料提供了另一种思路.

Recent development of efficient electrocatalysts derived from porous organic polymers for oxygen reduction reaction

Porous organic polymers(POPs) have recently emerged as promising candidates for catalyzing oxygen reduction reaction(ORR).Compared to conventional Pt-based ORR catalysts, these newly developed porous materials, including both non-precious metal based catalysts and metal-free catalysts, are more sustainable and cost-effective. Their porous structures and large surface areas facilitate mass and electron transport and boost the ORR kinetics. This mini-review will give a brief summary of recent development of POPs as electrocatalysts for the ORR. Some design principles, different POP structures, key factors for their ORR catalytic performance, and outlook of POP materials will be discussed.

In Situ Fabrication of Electrospun Carbon Nanofibers-Binary Metal Sulfides as Freestanding Electrode for Electrocatalytic Water Splitting

In search of effective and stable bifunctional electrocatalyst for electrocatalytic water splitting is still a major challenge for the highly efficient H_(2) production.Here,we reported a facile strategy to design high-indexed Cu_(3)Pd_(13)_S_(7) nanoparticles(NPs)in situ synthesized on the three-dimensional(3D)carbon nanofibers(CNFs)by combining electrospinning and chemical vapor deposition(CVD)technology.The high-index facets with abundant active sites,the 3D architecture CNFs with high specific surface area and synergistic effect of Cu-Pd-S bonds with strong electron couplings together promote the elec-trocatalytic performance.The Cu_(3)Pd_(13)_S_(7)/CNFs shows excellent electrocatalytic activity with low overpotentials of 52 mV(10 mA cm^(−2))for hydrogen evolution reaction(HER)and 240 mV(10 mA cm^(−2))for oxygen evolution reaction(OER).The excellent protection of Cu_(3)Pd_(13)_S_(7) by CNFs from aggregation and electrolyte corrosion lead to the high stability of Cu_(3)Pd_(13)_S_(7)/CNFs under acidic and alkaline conditions.