Hydrogen-Bond Network Promotes Water Splitting on the TiO₂ Surface

Abstract

Breaking the strong covalent O–H bond of an isolated H2O molecule is difficult, but it can be largely facilitated when the H2O molecule is connected with others through hydrogen-bonding. How a hydrogen-bond network forms and performs becomes crucial for water splitting in natural photosynthesis and artificial photocatalysis and is awaiting a microscopic and spectroscopic understanding at the molecular level. At the prototypical photocatalytic H2O/anatase-TiO2(001)-(1×4) interface, we report the hydrogen-bond network can promote the coupled proton and hole transfer for water splitting. The formation of a hydrogen-bond network is controlled by precisely tuning the coverage of water to above one monolayer. Under ultraviolet (UV) light irradiation, the hydrogen-bond network opens a cascaded channel for the transfer of a photoexcited hole, concomitant with the release of the proton to form surface hydroxyl groups. The yielded hydroxyl groups provide excess electrons to the TiO2 surface, causing the reduction of Ti4+ to Ti3+ and leading to the emergence of gap states, as monitored by in situ UV/X-ray photoelectron spectroscopy. The density functional theory calculation reveals that the water splitting becomes an exothermic process through hole oxidation with the assistance of the hydrogen-bond network. In addition to the widely concerned exotic activity from photocatalysts, our study demonstrates the internal hydrogen-bond network, which is ubiquitous at practical aqueous/catalyst interfaces, is also indispensable for water splitting.

Targeted H2O activation to manipulate the selective photocatalytic reduction of CO2to CH3OH over carbon nitride-supported cobalt sulfide

“…In the photocatalytic H 2 O activation process, protons are generated by oxidizing H 2 O with photogenerated holes (H 2 O + h + → • OH + H + ), while the photoreduction of H 2 O can only generate H 2 without the generation of protons (H 2 O + e − → OH − + 1/2H 2 ). 55,56 Moreover, the production of protons is controlled by the sluggish reaction kinetics in the photocatalytic oxidation of H 2 O. 57,58 This means that reducing the activation energy of H 2 O oxidation can help facilitate the generation of protons.…”

Modulating the Interfacial Water Network of Dual-Site Pd/FeOx/C Catalyst for Efficient Formate Electrooxidation

“…Based on this work, we further expect that engineering a functional interface between Pd catalyst and its substrate could be an effective strategy of tailoring the kinetic of FOR . Meanwhile, we noted that water molecules play a crucial role in the electrooxidation of organic fuels and disturbing the interfacial water network is conducive to the dissociation of water, − while tailoring the water network between the interface between Pd and substrate might be a possible avenue of inhibiting the catalysts deactivation caused by H ad . − To testify the hypothesis, herein, we designed a dual site Pd/FeO x /C catalyst by introducing iron oxides (FeO x ) as an assistant site to activate water molecules at the interface of Pd/C. − Iron oxides (FeO x ) with promising oxyphilic ability were codeposited on pristine Pd/C, resulting in a functional interface to modulate the interaction properties between water molecules and the catalyst. Electrochemical characterizations showed that the sharp peak featuring the H ad was nearly disappeared over the as-prepared Pd/FeO x /C catalyst, indicating a successfully removing of the H ad with the assistance of functional interface.…”

Thickness Control of BiOIO3 Enables Polarization Enhancement To Promote Carrier Separation and Pyro-PEC Performance

“…Therefore, the use of solar energy to produce hydrogen is promising as a new energy source to replace traditional fossil, and it is considered to be a reliable solution to the above problems. Since Honda and Fujishima discovered that TiO 2 can be used for PEC water splitting in 1972, a large number of semiconductor materials that can be used for solar hydrogen production have been widely studied, such as WO 3 , − TiO 2 , − Fe 2 O 3 , , and BiVO 4 − have become hot spots for research. However, there are many limitations in practical applications, the low carrier separation efficiency and high carrier compounding during migration to the surface are the biggest problems affecting the photocatalytic efficiency .…”