Conversion of bimetallic MOF to Ru-doped Cu electrocatalysts for efficient hydrogen evolution in alkaline media

The rational design and construction of inexpensive and highly active electrocatalysts for hydrogen evolution reaction(HER)is of great importance for water splitting.Herein,we develop a facile approach for preparation of porous carbon-confined Ru-doped Cu nanoparticles(denoted as Ru-Cu@C)by direct pyrolysis of the Ru-exchanged Cu-BTC metal–organic framework.When served as the electrocatalyst for HER,strikingly,the obtained Ru-Cu@C catalyst exhibits an ultralow overpotential(only 20 mV at 10 mA cm^(-2))with a small Tafel slope of 37 m V dec^(-1)in alkaline electrolyte.The excellent performance is comparable or even superior to that of commercial Pt/C catalyst.Density functional theory(DFT)calculations confirm that introducing Ru atoms into Cu nanocrystals can significantly alter the desorption of H_(2) to achieve a close-to-zero hydrogen adsorption energy and thereby boost the HER process.This strategy gives a fresh impetus to explore low-cost and high-performance catalysts for HER in alkaline media.

Long-term and short-term plasticity independently mimicked in highly reliable Ru-doped Ge_(2)Sb_(2)Te_(5) electronic synapses

In order to fulfill the complex cognitive behaviors in neuromorphic systems with reduced peripheral circuits,the reliable electronic synapses mimicked by single device that achieves diverse long-term and short-term plasticity are essential.Phase change random access memory(PCRAM)is of great potential for artificial synapses,which faces,however,difficulty to realize short-term plasticity due to the long-lasting resistance drift.This work reports the ruthenium-doped Ge_(2)Sb_(2)Te_(5)(RuGST)based PCRAM,demonstrating a series of synaptic behaviors of short-term potentiation,pair-pulse facilitation,longterm depression,and short-term plasticity in the same single device.The optimized RuGST electronic synapse with the high transformation temperature of hexagonal phase>380
C,the outstanding endurance>108 cycles,the low resistance drift factor of 0.092,as well as the extremely high linearity with correlation coefficients of 0.999 and 0.976 in parts of potentiation and depression.Further investigations also go insight to mechanisms of Ru doping according to thorough microstructure characterization,revealing that Ru dopant is able to enter GST lattices thus changing and stabilizing atomic arrangement of GST.This leads to the short-term plasticity realized by RuGST PCRAM.Eventually,the proposed RuGST electronic synapses performs a high accuracy of94.1%in a task of image recognition of CIFAR-100 database using ResNet 101.This work promotes the development of PCRAM platforms for large-scale neuromorphic systems.

Promoting nitric oxide electroreduction to ammonia over electron-rich Cu modulated by Ru doping

Electrocatalytic nitric oxide(NO)reduction is a promising strategy to produce ammonia.Developing a facile approach to synthesize efficient catalysts with enhanced NO electroreduction performance is highly desirable.Here,a series of Ru-doped Cu materials are constructed through in situ electroreduction of corresponding metal hydroxides.The optimized Ru_(0.05)Cu_(0.95)exhibits superior electrocatalytic performance for ammonia synthesis by using NO/Ar(1/4,n/n)as the feedstocks(Faradaic efficiency:64.9%,yield rate:17.68μmol cm^(-2)h^(-1)),obviously outperforming Cu counterpart(Faradaic efficiency:33.0%,yield rate:5.73μmol cm^(-2)h^(-1)).Electrochemical in situ Fourier transform infrared(FTIR)spectroscopy and online differential electrochemical mass spectrometry(DEMS)are adopted to detect intermediates and unveil the possible reaction pathway.The downshift of the Cu d-band center induced by Ru doping facilitates the rate-limiting hydrogenation step and decreases the desorption energy of NH_(3),leading to high Faradaic efficiency and yield of ammonia.