Amorphous carbon nitride (ACN) with a bandgap of 1.90 eV shows an order of magnitude higher photocatalytic activity in hydrogen evolution under visible light than partially crystalline graphitic carbon nitride with a bandgap of 2.82 eV. ACN is photocatalytically active under visible light at a wavelength beyond 600 nm.

A novel reduced melon photocatalyst with a bandgap of 2.03 eV developed here has a widened visible light absorption range and suppressed radiative recombination of photo-excited charge carriers due to the homogeneous self-modification with nitrogen vacancies. As a consequence, the reduced melon shows a much superior photocatalytic activity compared to the pristine melon in generating •OH radicals and degrading the organic pollutant Rhodamine B.

Selective breaking of the hydrogen bonds of graphitic carbon nitride can introduce favorable features, including increased band tails close to the band edges and the creation of abundant pores. These features can simultaneously improve the three basic processes of photocatalysis. As a consequence, the photocatalytic hydrogen-generation activity of carbon nitride under visible light is drastically increased by tens of times.

The selectivity of the CO2 photoreduction reaction in the presence of water vapour can be modulated by the band structure of a g-C3N4 photocatalyst. The major products obtained using bulk g-C3N4 with a bandgap of 2.77 eV and g-C3N4 nanosheets with a bandgap of 2.97 eV are acetaldehyde (CH3CHO) and methane (CH4), respectively.

Increasing visible light absorption of classic wide-bandgap photocatalysts like TiO has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry of these photocatalysts is essential to narrow their bandgap for a strong visible-light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail-like absorption band in hydrogen-free oxygen-deficient TiO , an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO by intentionally introducing atomic hydrogen-mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo-electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide-bandgap semiconductors to fully capture solar light.

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Semiconductor photocatalysis is an attractive approach to efficient solar energy conversion, reliant on appropriately engineered band structures to promote surface reactions under light irradiation. There are three fundamental factors for consideration in the design and development of semiconductor photocatalysts: (i) light absorption, (ii) separation and transport of photogenerated electrons and holes in bulk, and (iii) their transfer on the surface. [1][2][3][4][5] As a quintessential example of semiconductor photocatalysts, transition metal oxides and nitrides, in which valence band maxima and conduction band minima consists of anionic p states and cationic d states, respectively, always suffer from the much smaller mobility of holes in the valence band than electrons in the conduction band due to the intrinsically smaller slope of p states than d states at the extrema. [6][7][8][9] Under light irradiation, this imbalance could lead to a larger population or a higher probability of surface-reaching electrons than that of holes. As a consequence, the photocatalytic activity is largely compromised because most photocatalytic reactions, including hydrogen release from water splitting or a water/electron scavenger mixture, are controlled by (multi)holes involved in

Integrating a semiconducting light absorber with an appropriate co-catalyst appears almost indispensable for photocatalytic solar fuel generation. Although ferroelectric materials with spontaneous electrical polarization are considered promising light absorbers with the ability to induce oppositely directed transport of photogenerated electrons and holes in the bulk, their applications are intrinsically restricted by the large Schottky barrier at the interface of the ferroelectric material and the co-catalyst, which has a larger work function. Here, we demonstrate that, by selective chemical epitaxial growth of anatase TiO 2 islands on the positively poled (00-1) facet of PbTiO 3 single-crystal particles to form an atomically smooth interface with a small potential difference, the material shows significantly improved photocatalytic hydrogen and oxygen generation under both UV-visible and visible light, while the island-free PbTiO 3 is inactive in visible light. This strategy may be applicable to various ferroelectric materials to produce unusual asymmetric micro-nano structures for excellent performance.