Millisecond synthesis of CoS nanopartides for highly efficient overall water splitting

High performance and low-cost electrocatalysts for overall water splitting,i.e.,catalyzing hydrogen and oxygen evolution reactions with the same material,are of great importance for large-scale,renewable energy conversion processes.Here,we report an ultrafast(~7 ms)synthesis tech nique for tran sition metal chalcoge nide n anoparticles assisted by high temperature treatme nt.As a proof of con cept,we dem on strate that cobalt sulfide(~20 nm in diameter)@few-layer graphe ne(~2 nm in thick ness)core-shell nan oparticles embedded in RGO nano sheets exhibit remarkable bifunctional electrocatalytic activity and stability for overall water splitting,which is comparable to commercial 40 wt.%platinum/carbon(Pt/C)electrocatalysts.After 60 h of continuous operation,10 mA crrT?water splitting current density can still be achieved at a low potential of^1.77 V without any activity decay,which is among the most active for non-noble material based electrocatalysts.The presented study provides prospects in synthesizing highly efficient bifunctional electrocatalysts for large-scale energy conversion application via a simple yet efficient technique.

Catalyst-Free In Situ Carbon Nanotube Growth in Confined Space via High Temperature Gradient

Carbonaceous materials,such as graphite,carbon nanotubes(CNTs),and graphene,are in high demand for a broad range of applications,including batteries,capacitors,and composite materials.Studies on the transformation between diferent types of carbon,especially from abundant and low-cost carbon to high-end carbon allotropes,have received surging interest.Here,we report that,without a catalyst or an external carbon source,biomass-derived amorphous carbon and defective reduced graphene oxide(RGO)can be quickly transformed into CNTs in highly confned spaces by high temperature Joule heating.Combined with experimental measurements and molecular dynamics simulations,we propose that Joule heating induces a high local temperature at defect sites due to the corresponding high local resistance.Te resultant temperature gradient in amorphous carbon or RGO drives the migration of carbon atoms and promotes the growth of CNTs without using a catalyst or external carbon source.Our fndings on the growth of CNTs in confned spaces by fast high temperature Joule heating shed light on the controlled transition between diferent carbon allotropes,which can be extended to the growth of other high aspect ratio nanomaterials.