Growth of p-Type Hematite by Atomic Layer Deposition and Its Utilization for Improved Solar Water Splitting

Abstract

Mg-doped hematite (α-Fe(2)O(3)) was synthesized by atomic layer deposition (ALD). The resulting material was identified as p-type with a hole concentration of ca. 1.7 × 10(15) cm(-3). When grown on n-type hematite, the p-type layer was found to create a built-in field that could be used to assist photoelectrochemical water splitting reactions. A nominal 200 mV turn-on voltage shift toward the cathodic direction was measured, which is comparable to what has been measured using water oxidation catalysts. This result suggests that it is possible to achieve desired energetics for solar water splitting directly on metal oxides through advanced material preparations. Similar approaches may be used to mitigate problems caused by energy mismatch between water redox potentials and the band edges of hematite and many other low-cost metal oxides, enabling practical solar water splitting as a means for solar energy storage.

WS2 as an Effective Noble-Metal Free Cocatalyst Modified TiSi2 for Enhanced Photocatalytic Hydrogen Evolution under Visible Light Irradiation

“…Due to growing environmental concerns and increasing energy demands, hydrogen, as the highest energy density carrier per unit weight and an environmentally friendly energy source, has attracted great attention [1][2][3][4][5][6]. Since the discovery of hydrogen evolution through the photoelectrochemical water splitting on the TiO 2 electrode [7], photocatalytic water splitting to produce hydrogen under solar light irradiation has been considered as one of the most important approaches to meet the world energy demands and to solve environmental issues.…”

The Principle of Photoelectrochemical Water Splitting

“…Fe 2 O 3 is a typical n-type semiconductor due to oxygen vacancies. It can be changed to p-type through Mg doping [28]. Efforts have been devoted to improving the conductivity of hematite via doping with Ti, Si and Sn, and these impurity dopants are supposed to contribute to the enhancement of photocurrent.…”

“…Even without any addition of oxygen-evolving catalysts, photocurrents of 1.6 and 2.7 mA·cm −2 at 1.23 and 1.53 V vs. RHE, respectively, were obtained ( Figure 18(b)). [33]. Copyright @ American Chemical Society.…”

Branched nanostructures for photoelectrochemical water splitting

“…They have been widely applied in electronics, sensors, catalysts and more recently energy conversion/storage devices due to their environmental friendliness, abundance, low cost and/or stability. 3,4,9,10,16,[34][35][36][37] Morphologytunable synthesis of their nanostructures is substantially crucial for exploring their further potentials and for enabling scientists with great manipulation power on material and device performance. 10 There are manifold synthesis methods reported in the literature for their nanostructures, including hydrothermal synthesis, vapourliquid-solid (VLS) process, chemical vapour deposition (CVD) and microwave irradiation synthesis.…”