Z-scheme heterojunction Zn3(OH)2(V2O7)(H2O)2/V-Zn(O,S) for enhanced visible-light photocatalytic N2 fixation via synergistic heterovalent vanadium states and oxygen vacancy defects

Herein, we established a Zn 3 (OH) 2 (V 2 O 7 )(H 2 O) 2 /V-Zn(O,S) Z-scheme heterojunction (labeled ZnVO/V-Zn(O,S) with a heterovalent V 4+ /V 5+ states and oxygen vacancies in both phases via a one-step in-situ hydrolysis method. The NaBH 4 regulated the ZnVO/V-Zn(O,S)-3 with rich Vo and suitable n (V 4+ )/ n (V 5+ ) ratio achieved an excellent photocatalytic nitrogen fixation activity of 301.7 μmol/(g·h) and apparent quantum efficiency of 1.148% at 420 nm without any sacrificial agent, which is 11 times than that of V-Zn(O,S). The Vo acts as the active site to trap and activate N 2 molecules and to trap and activate H 2 O to produce the H for N 2 molecules photocatalytic reduction. The rich Vo defects can also reduce the competitive adsorption of H 2 O and N 2 molecules on the surface active site of the catalyst. The heterovalent vanadium states act as the photogenerated electrons, quickly hopping between V 4+ and V 5+ to transfer for the photocatalytic N 2 reduction reaction. Additionally, the Z-scheme heterojunction effectively minimizes photogenerated carrier recombination. These synergistic effects collectively boost the photocatalytic nitrogen fixation activity. This study provides a practical method for designing Z-scheme heterojunctions for efficient photocatalytic N 2 fixation under mild conditions. The Zn 3 (OH) 2 (V 2 O 7 )(H 2 O) 2 /V-Zn(O,S) Z-scheme heterojunction with rich Vo and suitable n (V 4+ )/ n (V 5+ ) ratio achieved an excellent photocatalytic nitrogen fixation activity of 301.7 μmol/(g·h) and apparent quantum efficiency of 1.148% at 420 nm in pure water.