Silicon photoanodes patterned with thin-film Ni catalyst islands exhibited stable oxygen evolution for over 240 h of continuous operation in 1.0 mol L⁻¹ KOH under simulated sunlight conditions. Buried-junction np⁺-Si(111) photoanodes with an 18.0% filling fraction of a square array of Ni microelectrodes, np⁺-Si(111)|NiμE_18.0%, demonstrated performance equivalent to a Ni anode in series with a photovoltaic device having an open-circuit voltage of 538 ± 20 mV, a short-circuit current density of 20.4 ± 1.3 mA cm⁻², and a photovoltaic efficiency of 6.7 ± 0.9%. For the np⁺-Si(111)|NiμE_18.0% samples, the photocurrent density at the equilibrium potential for oxygen evolution was 12.7 ± 0.9 mA cm⁻², yielding an ideal regenerative cell solar-to-oxygen conversion efficiency of 0.47 ± 0.07%. The photocurrent passed exclusively through the Ni catalyst islands to evolve O₂ with nearly 100% faradaic efficiency, while a passivating, insulating surface layer of SiO_x formed in situ on areas of the Si in direct contact with the electrolyte. The (photo)electrochemical behavior of Si electrodes patterned with varying areal filling fractions of Ni catalyst islands was also investigated. The stability and efficiency of the patterned-catalyst Si electrodes were affected by the filling fraction of the Ni catalyst, the orientation and dopant type of the substrates, and the measurement conditions. The electrochemical behavior at different stages of operation, including Ni catalyst activation, Si passivation, stable operation, and device failure, was affected by the dynamic processes of anodic formation and isotropic dissolution of SiO_x on the exposed Si. Ex situ and operando microscopic and spectroscopic studies revealed that these processes were three-dimensional and spatially non-uniform across the surface of the substrate, and occurred near the active catalyst islands. The patterned catalyst/substrate electrodes serve as a model system for accelerated studies of failure mechanisms in photoanodes protected by multifunctional catalytic coatings or other hole-conductive thin-film coatings that contain defects.

中文翻译：

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薄膜镍催化剂岛构图的水氧化硅阳极的性能和失效模式

在模拟的阳光条件下，在1.0 mol L ^-1 KOH中，用薄膜Ni催化剂岛构图的硅光电阳极在超过240小时的连续运行中表现出稳定的氧放出。具有Ni微电极方形阵列np ⁺ -Si（111）|NiμE18.0 _％的18.0％填充率的埋入式np ⁺ -Si（111）光电阳极表现出与与光伏器件串联的Ni阳极等效的性能具有538±20mV的开路电压，20.4±1.3mA cm ^-2的短路电流密度和6.7±0.9％的光伏效率。对于np ⁺ -Si（111）|NiμE18.0 _％在样品中，在氧气释放的平衡电势下的光电流密度为12.7±0.9 mA cm ^-2，产生的理想再生电池太阳能到氧气的转换效率为0.47±0.07％。光电流仅通过Ni催化剂岛，以近100％的法拉第效率释放出O ₂，同时原位形成SiO _x的钝化绝缘表面层在与电解质直接接触的硅区域上。还研究了用Ni催化剂岛的不同面积填充率构图的Si电极的（光）电化学行为。图案化的催化剂Si电极的稳定性和效率受Ni催化剂的填充率，基底的取向和掺杂剂类型以及测量条件的影响。在暴露的Si上形成SiO _x的阳极形成过程和各向同性溶解的动力学过程影响着操作的不同阶段的电化学行为，包括Ni催化剂活化，Si钝化，稳定的操作和器件故障。易地而operando显微镜和光谱学研究表明，这些过程是三维的，整个基材表面在空间上是不均匀的，并且发生在活性催化剂岛附近。图案化的催化剂/底物电极用作模型系统，用于加速研究由多功能催化涂层或其他包含缺陷的空穴传导性薄膜涂层保护的光阳极的失效机理。