RhO2修饰BiVO4薄膜光阳极的制备及其光电催化分解水性能

钒酸铋是最具有光电催化应用潜力的水分解光电阳极之一, 但由于表面缓慢的动力学反应速率, 其光电催化效率仍不理想。本研究通过浸渍法在BiVO₄薄膜光阳极上负载纳米RhO₂助催化剂, 研究RhO₂负载量对BiVO₄光阳极光电催化性能的影响规律及其机理。晶粒尺寸10~25 nm的RhO₂均匀负载在颗粒尺寸100~250 nm、厚度约为400 nm的BiVO₄光阳极薄膜表面。考虑到贵金属铑的昂贵成本, RhO₂的最佳负载量为质量分数1.65%, 在偏压1.23 V (vs. RHE)、1.0 mol/L Na₂SO₃溶液中(pH8.5)AM 1.5模拟可见光照射下, 光电流密度达3.81 mA·cm^-2, 相较纯BiVO₄提升了10.58倍。在没有有机牺牲剂的条件下, 光阳极同时析出了氢气和氧气, 两者比例接近2 : 1, 产氧速率为8.22 μmol/(h·cm²)。负载RhO₂有效改善了光阳极的表面水氧化动力学, 使光生空穴更快与电解质溶液进行水氧化反应, 抑制光生载流子复合, 从而显著提升光电催化性能。另外, 负载RhO₂后, 空穴更容易从光阳极表面被有效提取到电解质溶液中, 减少其在光阳极表面积累, 从而使BiVO₄/RhO₂(1.65%)光阳极可持续稳定工作10 h以上。

RhO2 Modified BiVO4 Thin Film Photoanodes: Preparation and Photoelectrocatalytic Water Splitting Performance

Bismuth vanadate is one of the most promising photoanodes for photoelectrocatalytic water splitting, however, its photoelectrocatalytic efficiency is still not ideal due to its sluggish kinetic reaction rate. The RhO₂ cocatalyst was loaded on the BiVO₄ thin film photoanode by impregnation method, and the photoelectrochenucal performance of the BiVO₄ photoanode with different RhO₂ loadings was studied. RhO₂ with grain size of 10-25 nm was uniformly loaded on the BiVO₄ film with grain size of 100-250 nm and thickness of 400 nm. The BiVO₄ photoanode with 1.65% RhO₂ (mass percent) showed the best comprehensive performance, of which the visible-light photocurrent density reached 3.81 mA·cm^-2 under 1.23 V (vs. RHE) in 1.0 mol/L Na₂SO₃ (pH8.5) electrolyte, which was 10.58 times higher than that of bare BiVO₄. In the absence of any sacrificial agent, the photoanodes produced hydrogen and oxygen at the same time at the ratio of close to 2 : 1, and the oxygen production rate was 8.22 µmol/(h·cm²). RhO₂ loading effectively improved the surface water oxidation kinetics, so that photogenerated holes could undergo water oxidation reaction more quickly. Meanwhile, the photogenerated carrier recombination was inhibited, significantly improving the photoelectrocatalytic performance. In addition, since holes were more easily extracted from the surface of photoanode into electrolyte solution in the presence of RhO₂ cocatalyst, reducing accumulation on the surface of the photoanode, the BiVO₄/RhO₂ (1.65%) photoanode achieved excellent stability for more than 10 h.