CHIH-JUNG CHENChen, Po-TzuPo-TzuChenBasu, MrinmoyeeMrinmoyeeBasuYang, Kai-ChihKai-ChihYangLu, Ying-RuiYing-RuiLuDong, Chung-LiChung-LiDongMa, Chong-GengChong-GengMaShen, Chin-ChangChin-ChangShenHu, Shu-FenShu-FenHuRU-SHI LIU2018-09-102018-09-102015http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000365216000047&KeyUID=WOS:000365216000047http://scholars.lib.ntu.edu.tw/handle/123456789/390950An integrated cobalt disulfide (CoS2) co-catalyst passivation layer on Si microwires (MWs) was used as a photocathode for solar hydrogen evolution. Si MWs were prepared by photolithography and dry etching techniques. The CoS2-Si photocathodes were subsequently prepared by chemical deposition and thermal sulfidation of the Co(OH)2 outer shell. The optimized onset potential and photocurrent of the CoS2-Si electrode were 0.248 V and -3.22 mA cm-2 (at 0 V), respectively. The best photocatalytic activity of the CoS2-Si electrode resulted from lower charge transfer resistances among the photoabsorber, co-catalyst, and redox couples in the electrolyte. X-ray absorption near edge structure was conducted to investigate the unoccupied electronic states of the CoS2 layer. We propose that more vacancies in the S-3p unoccupied states of the CoS2-Si electrode were present with a lower negative charge of S22- to form weaker S-H bond strength, promoting water splitting efficiency. Moreover, the CoS2 co-catalyst that completely covered underlying Si MWs served as a passivation layer to prevent oxidation and reduce degradation during photoelectrochemical measurements. Therefore, the optimal CoS2-Si electrode maintained the photocurrent at about -3 mA cm-2 (at 0 V) for 9 h, and its hydrogen generation rate was approximately 0.833 μmol min-1. © 2015 The Royal Society of Chemistry.[SDGs]SDG7Catalysts; Charge transfer; Cobalt; Electrochemistry; Electrodes; Electrolytes; Electronic states; Field emission cathodes; Hydrogen production; Passivation; Photocathodes; Photolithography; Silicon; Solar power generation; X ray absorption; X ray absorption near edge structure spectroscopy; Charge transfer resistance; Dry etching techniques; Hydrogen generations; Photocatalytic activities; Photoelectrochemical hydrogen; Photoelectrochemical measurements; Unoccupied electronic state; X ray absorption near edge structure; Transition metal compoundsjournal article10.1039/c5ta06202kWOS:000365216000047