Optimizing Surface Composition and Structure of FeWO₄ Photoanodes for Enhanced Water Photooxidation

Abstract

Photoelectrochemical water splitting is a promising approach to produce green hydrogen using solar energy. A primary bottleneck remains the lack of efficient photoanodes to catalyze the sluggish water photooxidation reaction. Engineering photoabsorbers with a narrow bandgap and suitable band edge can boost the photoelectrochemical performance. Herein, nanostructured iron tungstate (FeWO4) photoanodes are engineered directly on a fluorine doped tin oxide glass substrate via a scalable and ultra‐fast flame synthesis route in 13 seconds. Physiochemical, optoelectronic, and electrochemical properties of these photoanodes are systematically investigated. The key roles of charge transport, transfer, and dissolution of W and Fe ions from the FeWO4 matrix within long‐term performance are revealed. Optimal FeWO4 photoanode with a bandgap of 1.82 eV and a FeOOH/NiOOH co‐catalyst coating shows an improved water photooxidation performance, reaching a photocurrent density of 0.23 mA cm−2 at 1.4 V versus reversible hydrogen electrode in 1 m potassium hydroxide. It further demonstrates relatively good photostability, maintaining ≈96% of photocurrent density after 1‐hour continuous photooxidation, albeit some trace of Fe, W and Ni elements dissolution. Insights on the photooxidation performance of nanostructured FeWO4 provide promising directions for the engineering of small band‐gap catalysts for a variety of photoelectrochemical applications.

Understanding the Role of (W, Mo, Sb) Dopants in the Catalyst Evolution and Activity Enhancement of Co3O4 during Water Electrolysis via In Situ Spectroelectrochemical Techniques

“…Different scan rates were used in the cyclic voltammetry measurement at the potential window of 1.05 to 1.10 V versus RHE to obtain the electrochemical capacitance current for the evaluation of the relative electrochemically active surface area. [62,63]…”

Development of ABO4‐type photoanodes for photoelectrochemical water splitting

“…For example, a nanostructured FeWO 4 photoanode was directly deposited on FTO via a scalable and ultrafast flame synthesis route. 287 The optimal FeWO 4 photoanode has a bandgap of 1.82 eV and a photocurrent density of 0.23 mA cm −2 at 1.4 V versus RHE after loading FeOOH and NiOOH cocatalysts (Figure 11G-I). Although FeWO 4 has a high light absorption ability, its photocurrent cannot be compared with that of BiVO 4 , which may be due to the rapid carrier recombination caused by the defects on the interface between FeWO 4 and the cocatalyst.…”

“…FeWO 4 is mostly used for photocatalytic water splitting or degrade pollutants, and there are only a few reports on photoanodes. For example, a nanostructured FeWO 4 photoanode was directly deposited on FTO via a scalable and ultrafast flame synthesis route 287 . The optimal FeWO 4 photoanode has a bandgap of 1.82 eV and a photocurrent density of 0.23 mA cm −2 at 1.4 V versus RHE after loading FeOOH and NiOOH cocatalysts (Figure 11G–I).…”