Abstract
Despite III-V semiconductors demonstrating extraordinary solar-to-hydrogen (STH) conversion efficiencies, high cost and poor stability greatly impede their practical implementation in photoelectrochemical (PEC) water splitting applications. Here, we present a simple and efficient strategy for III-V-based photoelectrodes that functionally and spatially decouples the light harvesting component of the device from the electrolysis part that eliminates parasitic light absorption, reduces the cost, and enhances the stability without any compromise in efficiency. The monolithically integrated PEC cell was fabricated by an epitaxial lift-off and transfer of inversely grown InGaP/GaAs to a robust Ni-substrate and the resultant photoanode exhibits an STH efficiency of ~9% with stability ~150 h. Moreover, with the ability to access both sides of the device, we constructed a fully-integrated, unassisted-wireless “artificial leaf” system with an STH efficiency of ~6%. The excellent efficiency and stability achieved herein are attributed to the light harvesting/catalysis decoupling scheme, which concurrently improves the optical, electrical, and electrocatalytic characteristics.
Highlights
Despite III-V semiconductors demonstrating extraordinary solar-to-hydrogen (STH) conversion efficiencies, high cost and poor stability greatly impede their practical implementation in photoelectrochemical (PEC) water splitting applications
Among various material systems considered for photoelectrochemical (PEC) solar fuel generation[9,10,11,12], III-V semiconductors have received significant attention because of their appropriate bandgap and electronic and transport properties, which are suitable for PEC water-splitting applications[13,14,15,16]
Extensive research efforts have been devoted over the past decade on surface protection and passivation materials for III-V and other photoelectrodes by the deposition of transition metals, metal oxides, or metal silicides, etc.[17,19,21,22,23,24,25,26]
Summary
Despite III-V semiconductors demonstrating extraordinary solar-to-hydrogen (STH) conversion efficiencies, high cost and poor stability greatly impede their practical implementation in photoelectrochemical (PEC) water splitting applications. Tandem systems composed of InGaP/GaAs double junction photoelectrodes have the potential to drive unassisted PEC water-splitting, with solarto-hydrogen conversion (STH) efficiencies of 10–19%14–20. Despite their excellent photophysical properties and record high efficiencies, the high cost and poor PEC stability prevent their real-world applications. There are insufficient options for further optimization of the cost, performance, and stability of current single sided PEC devices Such issues can be addressed by employing an innovative scheme of decoupling the optical absorption and electrocatalytic interfaces to synergistically enhance the optical, electrical, surface protection, and electrocatalysis of the overall PEC system. Vijselaar et al have explored the partial decoupling of light absorption and electrocatalysis through the spatioselective deposition of electrocatalysts on high-aspect-ratio Si microstructures[28], but such designs are cumbersome and challenging to achieve in scalable and efficient PV-PEC devices
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