Design,fabrication And Hydrogen Generation Performance Of TiO₂/Au Nanoring/p-Si Nanohole Heteronanostructure Photocathode

Nowadays,hydrogen is widely considered as an ideal green energy.Since Fujishima and Honda first demonstrated using TiO2 for solar water splitting to generate hydrogen in 1972,photoelectrochemical(PEC)water splitting has been regarded as one of the most promising ways to generate hydrogen by utilizing the renewable solar energy.Si with low material cost and earth abundance is a promising candidate for photoelectrode due to its wide light absorption range and long carrier diffusion distance.Nanostructures fabricated by nanofabrication technology will bring with Si enhanced anti-reflection property,which could improve the efficiency of the light absorption of the electrode.In addition,nanostructures could also increase the contact area of electrode/electrolyte,leading to a more efficient water splitting process.Herein,we prepared a Si substrate with nanohole arrays on it.Embedded Au nanoring(AuNR)arrays and TiO2 layer were introduced to form heteronanostructure(HN)arrays,which were applied in water splitting hydrogen production.Since the fabrication process is repeatable and controllable,we can fabricate nanostructure arrays with uniform and precise sizes.The Si nanohole(SiNH)arrays substrate was prepared by nanoimprint lithography and reactive ion etching.Then embedded AuNRs were fabricated by sputtering deposition and subsequent ion beam etching to remove the Au layer covering the horizontal Si surface.The cylindrical AuNR clinging to the side wall of SiNH could maximize the horizontal exposure area of Si substrate,avoiding loss of light harvesting caused by reflection and scattering of nanoparticles fabricated on horizontal surface of Si substrate and having little adverse effect on its light absorption.We studied the optical properties of the HN arrays by theory simulation and try to control the actual structure sizes close to the theoretical model.The design is supported by theory simulation and could lead to expectable PEC performance by precisely controlling the geometry and size of the HN.Through the simulation analysis,we know that the embedded AuNR could trigger localized surface plasmon resonance(LSPR).The LSPR brings about prominent enhancement of light harvesting ability and excites vast hot electrons under light illumination which could transfer across the Schottky junction formed by AuNR and TiO2 to contribute to the hydrogen evolution reaction.Our prepared HN arrays exhibited outstanding hydrogen production performance during the electrochemical measurement process.The sample with best performance owns an onset potential of 0.32 VRHE and the maximum photon-to-energy conversion efficiency reaches 13.3%.Meanwhile,the sample possesses great hydrogen production rate,which is attributed to the synergetic effect of an electrochemical and PEC process.It can be observed from the current density,reaching 50 mA/cm2 at a bias of-1 VRHE.The stability test results demonstrate that the NH electrode exhibits good and stable performance of hydrogen production.The experimental results are in good accordance with the simulation analysis.We conclude the working mechanism of the NH arrays in hydrogen generation process based on the experimental results and simulation analysis,and demonstrate the efficient generation,separation and transport process of carriers arising from the special structure.This work develops an innovative HN photocathode with great hydrogen production performance and may provide a new path to boost hydrogen production performance of electrodes by utilization of suitable materials in combination with a reasonable design of component structures.