We report the microwave-assisted synthesis of heterojunctions based on bismuth niobate (BiNbO₄) and tungsten oxide (WO₃). These architectures have been used as photoanodes for water splitting under simulated AM1.5G solar light. We show for the first time that by controlling temperature and irradiation power it is possible to tune the fraction of orthorhombic and triclinic phases in BiNbO₄ nanoparticles, with strong consequences on the photocatalytic capabilities of the resulting heterojunctions. XRD patterns show that lower temperatures and irradiation power favor the formation of triclinic BiNbO₄ arrangements, whereas the morphology of WO₃ films is straightforwardly controlled by the addition of weak acids in the reactional medium that enable the formation of wrinkle-rod or cube-like particles. The orthorhombic symmetry of BiNbO₄ is shown to decrease the bandgap energy, whereas wrinkle-rod nanoparticles of WO₃ provides a rough surface that enhances the interaction between the semiconductors. This strategy leads to heterojunction able to generate photocurrent densities more than one order of magnitude higher than of bare WO₃ film. Our findings demonstrate that the microwave-assisted route is a very attractive alternative to directly control crystalline structure and ultimately the photocatalytic performance of bismuth niobate- and tungsten oxide-based heterojunctions.

我们报道了基于铌酸铋（BiNbO ₄）和氧化钨（WO ₃）的异质结的微波辅助合成。这些体系结构已被用作模拟AM1.5G太阳光下的水分解光阳极。我们首次表明，通过控制温度和辐射功率，可以调节BiNbO ₄纳米颗粒中的正交相和三斜晶相的比例，这对所得异质结的光催化能力产生了严重影响。XRD图谱表明较低的温度和辐射功率有利于三斜BiNbO ₄排列的形成，而WO ₃的形态通过在反应介质中添加弱酸可以直接控制薄膜，从而形成褶皱棒或立方体状颗粒。BiNbO ₄的正交对称性可降低带隙能量，而WO _3的皱纹杆纳米颗粒可提供粗糙的表面，从而增强半导体之间的相互作用。这种策略导致异质结能够产生的光电流密度比裸WO ₃薄膜高出一个数量级。我们的发现表明，微波辅助途径是直接控制晶体结构并最终控制铌酸铋和氧化钨基异质结的光催化性能的非常有吸引力的替代方法。