###### Abstract
); [EMAIL_ADDRESS] (J.) Advanced Nano-Surface Research Group, Korea Basic Science Institute, Daejeon 34133, Korea Correspondence: [EMAIL_ADDRESS] (J.M. ); [EMAIL_ADDRESS] (U.S.); Tel. : +82-42-865-3652 (J.M. ); +82-62-530-1718 (U.S.)  
Footnote †: journal: Applied Physics Letters  
1
Footnote 1: Department of Materials Science & Engineering, Chonnam National University, Gwangju 61186, Korea; [EMAIL_ADDRESS] (Y.S. ); [EMAIL_ADDRESS] (J.J.) Advanced Nano-Surface Research Group, Korea Basic Science Institute, Daejeon 34133, Korea Correspondence: [EMAIL_ADDRESS] (J.M. ); [EMAIL_ADDRESS] (U.S.); Tel. : +82-42-865-3652 (J.M. ); +82-62-530-1718 (U.S.)  
Footnote †: journal: Applied Physics Letters  
1
Footnote 1: Department of Materials Science & Engineering, Chonnam National University, Gwangju 61186, Korea; [EMAIL_ADDRESS] (Y.S. ); [EMAIL_ADDRESS] (J.J.) Advanced Nano-Surface Research Group, Korea Basic Science Institute, Daejeon 34133, Korea Correspondence: [EMAIL_ADDRESS] (J.M. ); [EMAIL_ADDRESS] (U.S.);  
Footnote †: journal: Applied Physics Letters  
1
Footnote 1: Department of Materials Science & Engineering, Chonnam National University, Gwangju 61186, Korea; [EMAIL_ADDRESS] (Y.S. ); [EMAIL_ADDRESS] (J.) Advanced Nano-Surface Research Group, Korea Basic Science Institute, Daejeon 34133, Korea Correspondence: [EMAIL_ADDRESS] (J.M. ); [EMAIL_ADDRESS] (U.S.);  
Footnote †: journal: Applied Physics Letters  
1
Footnote 1: Department of Materials Science & Engineering, Chonnam National University, Gwangju 61186, Korea; [EMAIL_ADDRESS] (Y.S. ); [EMAIL_ADDRESS] (J.J.) Advanced Nano-Surface Research Group, Korea Basic Science Institute, Daejeon 34133, Korea Correspondence: [EMAIL_ADDRESS] (J.M. ); [EMAIL_ADDRESS] (U.S.);  
Footnote †: journal: Applied Physics Letters  
1
Footnote 1: Department of Materials Science & Engineering, Chonnam National University, Gwangju 61186, Korea; [EMAIL_ADDRESS] (Y.S. ); [EMAIL_ADDRESS] (J.J.) Advanced Nano-Surface Research Group, Korea Basic Science Institute, Daejeon 34133, Korea Correspondence: [EMAIL_ADDRESS] (J.M. ); [EMAIL_ADDRESS] (U.S.);  
Footnote †: journal: Applied Physics Letters  
1
Footnote 1: Department of Materials Science & Engineering, Chonnam National University, Gwangju 61186, Korea; [EMAIL_ADDRESS] (Y.S. ); [EMAIL_ADDRESS] (J.) Advanced Nano-Surface Research Group, Korea Basic Science Institute, Daejeon 34133, Korea Correspondence: [EMAIL_ADDRESS] (J.M. ); usim@jnu. However, using a silicon electrode is highly challenging due to the high overpotential required for the generation of hydrogen. Thus, developing highly efficient electrodes, which can overcome the drawbacks posed by silicon, is crucial. Various approaches, such as surface modifications considering the cost and natural abundance of the electrocatalyst, have been explored to improve the PEC response of one-dimensional silicon nanostructures, especially that of silicon nanowires (SiNWs). Owing to their narrow band structure, silicon-based photoelectrodes are employed as both photocathode and photoanode for water splitting reactions [8; 10; 11]. A fundamental problem observed with a low-band gap Si as a photocathode for H\({}_{2}\) generation is that the difference between the Si valence band edge and the H\({}^{+}\)/H\({}_{2}\) redox level is rather narrow, which limits the generated photovoltage [12; 13]. As an emerging class of two-dimensional material, graphene has attracted significant attention in numerous applications owing to its stability, higher surface area, better optical transparency, and high carrier mobility. Reduced graphene oxide (rGO), which is a carbon-based material, is often used for these applications, owing to its exceptional PEC water splitting capability and fast-interfacial charge transfer between the electrode surface and the electrolyte [14; 15; 16]. Considering these advantages, we used rGO as a co-catalyst for PEC water splitting reactions. Scheme 1 illustrates the functionalization of rGO on SiNW photocathode.