Carbon flowers as electrocatalysts for the reduction of oxygen to hydrogen peroxide

Small-scale and decentralized production of H_(2)O_(2)via electrochemical reduction of oxygen is of great benefit,especially for sanitization,air and water purification,as well as for a variety of chemical processes.The development of low-cost and highperformance catalysts for this reaction remains a key challenge.Carbon-based materials have drawn substantial research efforts in recent years due to their advantageous properties,such as high chemical stability and high tunability in active sites and morphology.Deeper understanding of structure–activity relationships can guide the design of improved catalysts.We hypothesize that mass transport to active sites is of great importance,and herein we use carbon materials with unique flower-like superstructures to achieve high activity and selectivity for O2 reduction to H_(2)O_(2).The abundance of nitrogen active sites controlled by pyrolysis temperature resulted in high catalytic activity and selectivity for oxygen reduction reaction(ORR).The flower superstructure showed higher performance than the spherical nanoparticles due to greater accessibility to the active sites.Chemical activation improves the catalysts’performances further,driving the production of H_(2)O_(2)to a record-setting rate of 816 mmol·gcat^(−1)·h^(−1)using a bulk electrolysis setup.This work demonstrates the development of a highly active catalyst for the sustainable production of H_(2)O_(2)through rational design and synthetic control.The understanding from this work provides further insight into the design of future carbon-based electrocatalysts.

On-demand production of hydrogen by reacting porous silicon nanowires with water

On-demand hydrogen generation is desired for fuel cells,energy storage,and clean energy applications.Silicon nanowires(SiNWs)and nanoparticles(SiNPs)have been reported to generate hydrogen by reacting with water,but these processes usually require external assistance,such as light,electricity or catalysts.Herein,we demonstrate that a porous SiNWs array,which is fabricated via the metal-assisted anodic etching(MAAE)method,reacts with water under ambient and dark conditions without any energy inputs.The reaction between the SiNWs and water generates hydrogen at a rate that is about ten times faster than the reported rates of other Si nanostructures.Two possible sources of enhancement are discussed:SiNWs maintain their high specific surface area as they don’t agglomerate,and the intrinsic strain of the nanowires promotes the reactivity.Moreover,the porous SiNWs array is portable,reusable,and environmentally friendly,yielding a promising route to produce hydrogen in a distributed manner.