Facial boron incorporation in hematite photoanode for enhanced photoelectrochemical water oxidation

Advanced hematite nanomaterials for newly emerging applications

Because of the combined merits of rich physicochemical properties, abundance, low toxicity, etc., hematite (α-Fe2O3), one of the most chemically stable compounds based on the transition metal element iron, is endowed with multifunctionalities and has steadily been a research hotspot for decades. Very recently, advanced α-Fe2O3 materials have also been developed for applications in some cutting-edge fields. To reflect this trend, the latest progress in developing α-Fe2O3 materials for newly emerging applications is reviewed with a particular focus on the relationship between composition/nanostructure-induced electronic structure modulation and practical performance. Moreover, perspectives on the critical challenges as well as opportunities for future development of diverse functionalities are also discussed. We believe that this timely review will not only stimulate further increasing interest in α-Fe2O3 materials but also provide a profound understanding and insight into the rational design of other materials based on transition metal elements for various applications.

Boron-passivated surface Fe(iv) defects in hematite for highly efficient water oxidation

Hematite is a good photocatalyst for solar water oxidation but its performance is highly limited by the strong electron-hole recombination. Surface defects as recombination centers were considered as one of the most important factors in determining the efficiency of hematite. However, the defects have never been clearly identified, which strongly limits the targeted modification. Here we report the identification of surface Fe(iv) defects in hematite by using synchrotron radiation based X-ray absorption spectroscopy. Moreover, the Fe(iv) defects can be effectively passivated by facile surface engineering with boron-termination, which can suppress the surface recombination and then significantly improve the performance. The B-passivated hematite thus shows a large cathodic shift (up to 100 mV) of the onset potential when compared to the pristine sample, and can be effectively coupled with Ti-treatment and Co-Pi co-catalyst to finally achieve a high photocurrent of 2.61 mA cm-2 at 1.23 V vs. RHE. The results may open up a new way by targeted surface engineering to effectively passivate the defects in hematite.