Synergetic Effect of Conjugated Ni(OH)₂/IrO₂ Cocatalyst on Titanium-Doped Hematite Photoanode for Solar Water Splitting

Abstract

Hematite is a promising photoanode material for renewable solar fuel production via photoelectrochemical (PEC) water splitting. However, the fast electron−hole recombination and sluggish surface reaction retard it from getting satisfied performance. Herein, hematite nanorod arrays doped with titanium (Ti−Fe 2 O 3 ) on the surface were prepared by a solutionbased process. Because of one-dimension anisotropy and improved charge transfer property, the photocurrent density is doubled compared to pure Fe 2 O 3 at 1.50 V vs RHE under simulated sunlight (AM 1.5 G) irradiation. Loading conjugated Ni(OH) 2 /IrO 2 cocatalyst further leads to about 200 mV negative shift of the onset potential and dramatic increase of the applied bias photon-to-current efficiency (ABPE). We find that Ni(OH) 2 can efficiently capture the photogenerated holes from hematite as a hole-storage layer (HSL) to improve the charge transfer process across the interface of hematite and IrO 2 electrocatalyst. Furthermore, the stored photogenerated holes in Ni(OH) 2 can be utilized by IrO 2 for water oxidation more facilely. This synergetic effect along with the efficient surface doping are proposed to be responsible for the enhanced performance.

Rational Design and Construction of Cocatalysts for Semiconductor‐Based Photo‐Electrochemical Oxygen Evolution: A Comprehensive Review

“…The achieved Ni 4+ ions are recognized as the actual active centers for water oxidation. For example, Wang et al [168] coupled Ni(OH) 2 with more active IrO 2 to realize its full catalytic activity (Figure 13c). Since then, strategies have been adopted to promote the activity and stability of Ni(OH) 2 .…”

Photoelectrode for water splitting: Materials, fabrication and characterization

“…It has reached a consensus that the PEC process has at least three key steps to utilize the solar energy, which are light harvest, charge separation and surface reaction as shown in Fig. 2, determined by the bulk and surface properties of the semiconductor [22,23]. For the light harvest of an electrode, the efficiency (η LH ) depends on the absorbance of the semiconductor which usually has close relationship with the bandgap of the semiconductor, transition model (direct or indirect transition), film thickness, etc.…”

“…In addition, the chemical bath method is another widely used method in FeOOH, Cu 2 O, NiOOH deposition [23,69,70]. Uniform films can be produced in the stock solution at ambient pressure below boiling point of solution.…”

Combining Bulk/Surface Engineering of Hematite To Synergistically Improve Its Photoelectrochemical Water Splitting Performance

“…Many attempts have also been made to enhance the charge transfer efficiency of Fe 2 O 3 . These include development of oxygen evolution catalysts (OEC) and formation of hole-storage layer 22 performance of Fe 2 O 3 , which includes Ti doping, dense layer for suppressing the back-injection of electron to FTO, and surface treatment, and consequently, all these processes promise a reduction of photocurrent onset potential of 380 mV. 4 Despite all these achievements, the facile fabrication of prominent PEC water splitting photoanode still remains a challenge.…”