Highly Efficient Photoelectrochemical Water Splitting: Surface Modification of Cobalt‐Phosphate‐Loaded Co₃O₄/Fe₂O₃ p–n Heterojunction Nanorod Arrays

Abstract

Hematite (α-Fe 2 O 3 ) as a photoanode material for photoelectrochemical (PEC) water splitting suffers from the two problems of poor charge separation and slow water oxidation kinetics. The construction of p-n junction nanostructures by coupling of highly stable Co 3 O 4 in aqueous alkaline environment to Fe 2 O 3 nanorod arrays with delicate energy band positions may be a challenging strategy for efficient PEC water oxidation. It is demonstrated that the designed p-Co 3 O 4 /n-Fe 2 O 3 junction exhibits superior photocurrent density, fast water oxidation kinetics, and remarkable charge injection and bulk separation efficiency (η inj and η sep ), attributing to the high catalytic behavior of Co 3 O 4 for the oxygen evolution reaction as well as the induced interfacial electric field that facilitates separation and transportation of charge carriers. In addition, a cocatalyst of cobalt phosphate (Co-Pi) is introduced, which brings the PEC performance to a high level. The resultant Co-Pi/Co 3 O 4 /Ti:Fe 2 O 3 photoanode shows a photocurrent density of 2.7 mA cm −2 at 1.23 V RHE (V vs reversible hydrogen electrode), 125% higher than that of the Ti:Fe 2 O 3 photoanode. The optimized η inj and η sep of 91.6 and 23.0% at 1.23 V RHE are achieved on Co-Pi/Co 3 O 4 /Ti:Fe 2 O 3 , respectively, corresponding to the 70 and 43% improvements compared with those of Ti:Fe 2 O 3 . Furthermore, Co-Pi/Co 3 O 4 /Ti:Fe 2 O 3 shows a low onset potential of 0.64 V RHE and long-time PEC stability.

Janus‐Structured Co‐Ti3C2 MXene Quantum Dots as a Schottky Catalyst for High‐Performance Photoelectrochemical Water Oxidation

“…To the best of our knowledge, the PEC water oxidation and stability of as constructed Co‐MQD photoelectrocatalyst are comparable or even superior to the works on other classical high performance photoanode materials, such as TiO 2 , [ 44,45 ] BiVO 4 , [ 46 ] Fe 2 O 3 , [ 47–52 ] ZnO, [ 53 ] and MoS 2 . [ 54 ] As shown in Table S5, Supporting Information, at a bias potential of 1.23 V versus RHE, the Co‐MQD‐48 photoanode achieves almost the highest current density of 2.99 mA cm −2 , making it among the state‐of‐the‐art performance in PEC water oxidation.…”

Significance of interface barrier at electrode of hematite hydroelectric cell for generating ecopower by water splitting

“…Research work has been foregoing on hydrogen‐based efficient energy economy development using solar/UV irradiation on water since last four decades in the form of artificial photosynthetic techniques . Tremendous efforts have been directed in improving the photoenergy conversion efficiency using sophisticated oxide based photoelectrodes in photoelectrochemical cells . However, higher cost, use of electrolyte, and the low conversion efficiency factor while using input solar/UV irradiation became dominant factors in its lacking industrialization prospects.…”

Surface sulfurization activating hematite nanorods for efficient photoelectrochemical water splitting

“…V oc, light is tested under simulated 1 sun (AM 1.5 G, 100 mW cm À2 ). The lifetime of photo-generated charge carriers (s n ) was determined with open-circuit potential by the following equation [34]:…”