Bifunctional NiFe inverse opal electrocatalysts with heterojunction Si solar cells for 9.54%-efficient unassisted solar water splitting. (December 2017)

• Record Type: Journal Article
• Authors: Song, Hakhyeon; Oh, Seungtaeg; Yoon, Hyun; Kim, Ka-Hyun; Ryu, Sangwoo; Oh, Jihun
• Is Part Of: Nano energy. Volume 42(2017:Dec.)
• Page Start: 1
• Page End: 7
• Publication Date: 2017-12
• Subjects: Water splitting -- NiFe catalysts -- Inverse opal structures -- Photovoltaic-electrolyzer -- Solar-to-hydrogen efficiency; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2017.10.028
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Photovoltaic cell–electrolyzer combined systems have recently been considered a most promising route to commercialization of photoelectrochemical (PEC) water splitting although efficiency, stability, and cost remain major challenges. Herein, we develop a highly efficient and low-cost, bifunctional NiFe electrocatalyst that uses NiFe inverse opal nanostructures for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). From their increased surface area, NiFe inverse opal structures can reduce the overpotential by ~ 70 mV and ~ 90 mV for OER and HER, respectively. In addition, correlations between increased surface area of inverse opal 3-dimensional nanostructures and electrocatalytic activity of OER and HER are explored. Furthermore, a NiFe inverse opal structure with an optimized number of thickness layers reduces the overpotential of water splitting by ~160 mV. When integrated to four series-connected Si heterojunction (SHJ) solar cells, the NiFe inverse opal electrolyzer achieves a 9.54% solar-to-hydrogen conversion efficiency over 24 h under a zero-bias condition. The combined PEC water splitting investigated in this work is expected to provide a basis for the design of highly efficient renewable and sustainable water electrolysis systems that incorporate earth-abundant, low-cost materials. Graphical abstract: Highlights: Ordered NiFe-mesostructures for bifunctional electrocatalysts for water splitting. The role of nano- and meso-structures for catalytic activity is suggested. Combination of NiFe inverse opals and Si heterojunction solar cells. 9.54% unassisted solar to hydrogen conversion efficiency is achieved for 25 h.