Coupled Lead Halide Perovskite Photoelectrode for Unbiased Photoelectrochemical Water Splitting

Abstract

In search for new technology to preserve global warming caused by fossil fuel, solar energy driven devices have been high in demand. For instance, photovoltaics (PV) are a promising technology that can produce high power conversion efficiency (PCE). In addition, photoelectrochemical (PEC) water splitting, a promising artificial photosynthesis method, is a potential alternative technique to generate renewable fuel. PEC devices can generate renewable energy sources such as hydrogen, which can alleviate CO2 emission from fossil fuels. However, most readily employed PEC devices require external bias to function as a hydrogen producer. Thus, utilizing PV active layer as a photo absorber, PEC system is a suitable approach to the breakthrough of efficient hydrogen production.In the past decade of PV technology advances, organic-inorganic lead halide perovskite (LHP) can be arguably the most progressive research because of its tunable bandgap, fast charge separation, broad light absorption spectra, low cost, facile fabrication, and high efficiency. These advantageous properties led LHPs to be used as an active layer of water splitting devices. However, LHP-based PECs have flaws to be addressed to be viable material for PEC. LHP are known for their fragile nature from exposure to water. Hence, LHP-based PECs are commonly protected with metal foil encapsulation while covering the edges with epoxy resins. However, the metal foil provides poor contact with the LHP leading to poor charge transfer for water splitting. To solve this problem, we applied carbon conductive powder (CCP) as the interlayer to successfully facilitate charge transfer.With the proposed device modeling, monolithic PEC device that is capable of generating hydrogen in presence of low external applied bias is fabricated. Nonetheless, single monolithic PEC devices still need external applied bias to function as water splitting device which seek for further research. Therefore, adding another photoelectrode will eliminate the necessity of external bias resulting in an only solar powered water splitting device. Herein, we report unassisted solar to hydrogen conversion by using inverted and planar type LHP solar cells as photocathode and photoanode, respectively. With the integration of catalyst, 3D Ni.NiFe and NiPCoP, LHP-based PEC with exceptional performance was attained. We demonstrated unbiased PEC water splitting using a coupled LHP-based photoelectrode under alkaline conditions. Each LHP-based photoelectrode exhibited a outstanding performance of 22.42 mA cm-2 at 1.23 VRHE and 21.96 mA cm-2 at 0 VRHE for the photoanode and photocathode, respectively. Thus, we achieved solar to hydrogen (STH) of 10.64% and unassisted photo-current density of 8.65 mA/cm2. In addition, unbiased catalytic reactivity over 20 h retaining about 60% of photo-current density was attained.