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.

Effects and mechanisms of surfactants on physical properties and microstructures of metakaolin-based geopolymer

In this study,the effects of five different ionic and nonionic surfactants on the physical properties and microstructures of a metakaolin-based geopolymer(MKG)were investigated.It is the first comprehensive comparative study of the effects of sodium lauryl sulfonate(SLS),alkyl polyglycoside(APG),benzalkonium chloride(BAC),sucrose fatty acid esters(SE),and stearic acid(STA)on MKG.Viscosity,densities,apparent water absorption,and compressive strength were measured,and pore structures,micro-defects,and gels observed through scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP).In the MKG slurry,a high affinity of surfactants to liquid-air interfaces increased viscosity and promoted the generation of bubbles.Based on both the ionic types and molecular configurations of the surfactants,stronger adsorption of a surfactant on the surface of the metakaolin resulted in better dispersion of metakaolin particles and a denser microstructure of the MKG.The surfactants with weaker adsorption(SLS and APG)caused higher porosity,a larger pore size,and more micro-defects,while those with stronger adsorption(BAC,SE,and STA)led to relatively lower porosity and denser microstructures.Density,water absorption,and compressive strength were closely related to the total intrusion porosity of the MKG.The mechanisms underlying surfactant adsorption to the surface of metakaolin are proposed.