Herein, we demonstrated the controllable synthesis of a centimeter-scale two-dimensional (2D) ZnO-doped Ga 2 O 3 nanostructure layer by a liquid Ga−Zn alloy printing strategy at near room temperature. Different from the liquid Ga−In and Ga− In−Sn alloys, the surface oxidation behavior of a liquid Ga−Zn alloy follows an obvious competition and cooxidation characteristics instead of the dominant oxidation characteristic of Ga, which could be effectively used to precisely tailor the Zn content of 2D Ga 2 O 3 films. With an increase of the nominal Zn content in the Ga−Zn alloy from 0 to 8 atom %, the real Zn content of 2D ZnOdoped Ga 2 O 3 films gradually increases and finally reaches a maximum saturated value of 16−18 atom % at the eutectic component of 3.87 atom %. Correspondingly, the transmittance and band gap of 2D ZnO-doped Ga 2 O 3 films could also be tuned by changes of the Zn content and crystallinity. The method proposed in this work provides a general route toward the doping synthesis of a diverse nonlayered 2D structure, which will shed light on the applications of various displays and deep-ultraviolet optoelectronic devices.

Photoelectrochemical water splitting based on suitable catalysts has attracted wide attention as a promising strategy to utilize solar energy to produce clean and renewable hydrogen fuel. Herein, we reported cobalt phosphate-modified (GaN)1–x (ZnO) x /GaN nanowire arrays on a high-temperature conductive GaN substrate toward enhanced photoelectrochemical water splitting by a facile two-step Au-assisted chemical vapor deposition method. The highly conductive Si-doped GaN substrate is designed to serve as a current collector and epitaxial substrate to grow GaN nanowires at high temperature. Meanwhile, high density of branched (GaN)1–x (ZnO) x nanowires with a tunable band gap, strong visible-light absorption, and high catalytic activity is deposited on the surface of GaN nanowires to act as active components to harvest light toward the oxygen evolution reaction. Such multi-junction heterostructures effectively enhance wide spectral utilization and light absorption and simultaneously accelerate the separation of electrons and holes and the transfer of photogenerated electrons from (GaN)1–x (ZnO) x nanowires to the GaN substrate collector and Pt electrode. The photocurrent density of the (GaN)1–x (ZnO) x /GaN nanowire array photoanode can reach 37.5 μA cm–2 at 1.23 V vs reversible hydrogen electrode and could be further enhanced to 186 μA cm–2 by modifying the cobalt phosphate cocatalyst, showing promising potential in clean hydrogen production.