Hydrogen spillover bridged dual nano-islands triggered by built-in electric field for efficient and robust alkaline hydrogen evolution at ampere-level current density

Employing the alkaline water electrolysis system to generate hydrogen holds great prospects but still poses significant challenges,particularly for the construction of hydrogen evolution reaction(HER)catalysts operating at ampere-level current density.Herein,the unique Ru and RuP_(2)dual nano-islands are deliberately implanted on N-doped carbon substrate(denoted as Ru-RuP_(2)/NC),in which a built-in electric field(BEF)is spontaneously generated between Ru-RuP_(2)dual nano-islands driven by their work function difference.Experimental and theoretical results unveil that such constructed BEF could serve as the driving force for triggering fast hydrogen spillover process on bridged Ru-RuP_(2)dual nano-islands,which could invalidate the inhibitory effect of high hydrogen coverage at ampere-level current density,and synchronously speed up the water dissociation on Ru nano-islands and hydrogen adsorption/desorption on RuP_(2)nano-islands through hydrogen spillover process.As a result,the Ru-RuP_(2)/NC affords an ultra-low overpotential of 218 mV to achieve 1.0 A·cm^(−2)along with the superior stability over 1000 h,holding the great promising prospect in practical applications at ampere-level current density.More importantly,this work is the first to advance the scientific understanding of the relationship between the constructed BEF and hydrogen spillover process,which could be enlightening for the rational design of the cost-effective alkaline HER catalysts at ampere-level current density.

Engineering adjacent Fe_(3)C as proton-feeding centers to single Fe sites enabling boosted oxygen reduction reaction kinetics for robust Zn-air batteries at high current densities

Oxygen reduction reaction(ORR)plays an important role in the next-generation energy storage technologies,whereas it involves the sluggish and complicated proton-coupled electron transfer(PCET)steps that greatly limit the ORR kinetics.Therefore,it is urgent to construct an efficient catalyst that could simultaneously achieve the rapid oxygen-containing intermediates conversion and fast PCET process but remain challenging.Herein,the adjacent Fe_(3)C nanoparticles coupling with single Fe sites on the bubble-wrap-like porous N-doped carbon(Fe_(3)C@FeSA-NC)were deliberately constructed.Theoretical investigations reveal that the adjacent Fe_(3)C nanoparticles speed up the water dissociation and serve as proton-feeding centers for boosting the ORR kinetics of single Fe sites.Benefiting from the synergistic effect of the Fe_(3)C and single Fe sites,the Fe_(3)C@FeSA-NC affords an excellent half-wave potential of 0.88 V,and enables the assembled Zn-air batteries with the high peak power density of 164.5 mW·cm^(-2)and long-term stability of over 200 h at high current densities at 50 mA·cm^(-2).This work clarifies the mechanism for improving ORR kinetics of single atomic sites by engineering the adjacent proton-feeding centers,shedding light on the rational design of cost-effective electrocatalysts for energy conversion and storage technologies.

近邻Ni位点对双Fe中心电子自旋态调制实现催化剂增强的催化活性和锌空气电池超长稳定性

在锌空气电池(ZABs)领域中,开发具有优异氧还原反应(ORR)活性和超长期稳定性的Fe基单原子催化剂是一项充满挑战的任务.为此,本文在氮掺杂空心碳球上构建了近邻NiN4单原子位点和Fe_(2)N_(5)双原子位点共存的催化剂(Fe/Ni-NHCS),作为ZABs中高效稳定的空气阴极ORR电催化剂.理论计算和磁性测试结果均表明,近邻NiN_(4)位点的引入对优化Fe2Ns位点的电子自旋态和降低含氧中间体吸附和转化能垒起到关键作用,从而使得Fe/Ni-NHCS具有出色的ORR催化活性和极低的副产物HO_(2)产率。更重要的是,由Fe/Ni-NHCS作为空气阴极驱动的ZABs展现出超过1200h的长时间可充放电循环稳定性。该工作通过调制活性位点的自旋态同时实现了对于催化活性和稳定性的双重优化,从而为能量转换技术的发展拓展了一条新路径。

Controllable Ni/NiO interface engineering on N-doped carbon spheres for boosted alkaline water-to-hydrogen conversion by urea electrolysis

Interface engineering has gradually attracted substantial research interest in constructing active bifunctional catalysts toward urea electrolysis.The fundamental understanding of the crystallinity transition of the components on both sides of the interface is extremely significant for realizing controllable construction of catalysts through interface engineering,but it still remains a challenge.Herein,the Ni/NiO heterogenous nanoparticles are successfully fabricated on the porous N-doped carbon spheres by a facile hydrothermal and subsequent pyrolysis strategy.And for the first time we show the experimental observation that the Ni/NiO interface can be fine-tuned via simply tailoring the heating rate during pyrolysis process,in which the crystalline/amorphous or crystalline/crystalline Ni/NiO heterostructure is deliberately constructed on the porous N-doped carbon spheres(named as CA-Ni/NiO@NCS or CC-Ni/NiO@NCS,respectively).By taking advantage of the unique porous architecture and the synergistic effect between crystalline Ni and amorphous NiO,the well-designed CA-Ni/NiO@NCS displays more remarkable urea oxidation reaction(UOR)and hydrogen evolution reaction(HER)activity than its crystalline/crystalline counterpart of CC-Ni/NiO@NCS.Particularly,the whole assembled two-electrode electrolytic cell using the elaborate CANi/NiO@NCS both as the anode and cathode can realize the current density of 10 mA·cm^(−2)at a super low voltage of 1.475 V(264 mV less than that of pure water electrolysis),as well as remarkable prolonged stability over 63 h.Besides,the H_(2)evolution driven by an AA battery and a commercial solar cell is also studied to enlighten practical applications for the future.