Efficient design principle for interfacial charge separation in hydrogen-intercalated nonstoichiometric oxides. (November 2018) - Gu, Zhenao
Abstract: Establishing effective strategies to boost the separation of interfacial charge carriers is necessary to address the limiting bottlenecks of photocatalysis. Although oxygen vacancy modulation has become the prevalent strategy to improve the photoactivity, controversy persists regarding the real role of these defects in charge separation. To exert the great potential of nonstoichiometric semiconductors, one needs not only to establish a full atomistic picture of oxygen vacancies, but also to deliberate their possible interactions with other interfacial structures (represented by the ubiquitous intercalated hydrogen). Herein, WO3 was used as a typical model to demonstrate the principle of hydrogen-intercalated nonstoichiometric oxides for photoelectrochemical water splitting. Both experimental characterizations and theoretical calculations evidenced the synergetic interactions between oxygen vacancies and intercalated hydrogen. The sequential formation of subsurface defect clusters and surface O–H bonds contributed significantly to the spatial separation of charge carriers and the impressive stability of nonstoichiometric photoanodes. Profiting from this principle, an unprecedented photocurrent of 2.94 mA cm −2 at 1.23 V vs. RHE was achieved, apart from a 100 mV cathodic shift in the onset potential. Our principle is applicable to several semiconductors, e.g. TiO2 and Fe2 O3 . Thus, it opens up a promising avenue into designing high-performance nonstoichiometric nanoarchitectures for a wide range of applications. The termination-dependent surface reactivity also provides new opportunities of reactive species modulation for high-performance photocatalysis. Graphical abstract: fx1 Highlights: The principle of hydrogen-intercalated nonstoichiometric structures was demonstrated. The synergetic effects between oxygen vacancy and intercalated hydrogen was studied. Subsurface defect clusters and surface O-H bonds benefited the charge separation. Unprecedented photocurrent and impressive stability of WO3 photoanodes was achieved. Termination-dependent activity provided opportunity for reactive species modulation.