Enabling Si photoanodes for efficient solar water oxidation would facilitate the development of solar fuel conversion, but it is challenging owing to Si surface passivation via photo-induced corrosion in aqueous elect...Enabling Si photoanodes for efficient solar water oxidation would facilitate the development of solar fuel conversion, but it is challenging owing to Si surface passivation via photo-induced corrosion in aqueous electrolytes. To overcome this challenge, most approaches have focused on improving the stability of Si by coating dense and thin protective layers using high vacuum-based techniques such as atomic layer deposition. However, these procedures are costly, making scalability for practical applications difficult. Herein, we report a modified electroless deposition （ELD） method to uniformly deposit protective and catalytic Ni films on Si wafers, resulting in efficient and stable Si photoanodes for solar water oxidation. The optimized Ni/n-Si photoanode achieves an onset potential of -1.09 V vs. a reversible hydrogen electrode and a saturation current density of -27.5 mA/cm^2 under AM 1.5 G illumination at pH 14. The ELD method is additionally capable of Ni deposition on a 4-inch n-Si wafer, demonstrating the first 4-inch Si photoanode. The solar water oxidation of the ELD-Ni/n-Si photoanode can be further improved by surface texturing, built-in n-p junctions, or coupling with more efficient catalysts.展开更多
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 t...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.展开更多
文摘Enabling Si photoanodes for efficient solar water oxidation would facilitate the development of solar fuel conversion, but it is challenging owing to Si surface passivation via photo-induced corrosion in aqueous electrolytes. To overcome this challenge, most approaches have focused on improving the stability of Si by coating dense and thin protective layers using high vacuum-based techniques such as atomic layer deposition. However, these procedures are costly, making scalability for practical applications difficult. Herein, we report a modified electroless deposition （ELD） method to uniformly deposit protective and catalytic Ni films on Si wafers, resulting in efficient and stable Si photoanodes for solar water oxidation. The optimized Ni/n-Si photoanode achieves an onset potential of -1.09 V vs. a reversible hydrogen electrode and a saturation current density of -27.5 mA/cm^2 under AM 1.5 G illumination at pH 14. The ELD method is additionally capable of Ni deposition on a 4-inch n-Si wafer, demonstrating the first 4-inch Si photoanode. The solar water oxidation of the ELD-Ni/n-Si photoanode can be further improved by surface texturing, built-in n-p junctions, or coupling with more efficient catalysts.
基金The authors acknowledge the support of the California Energy Commission,Stanford Natural Gas Initiative,and Stanford Hydrogen Focus Group.Part of this work was performed at the Stanford Nano Shared Facilities(SNSF),supported by the National Science Foundation under award ECCS-1542152.
文摘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.
