The photoelectrochemical splitting of water into hydrogen and oxygen requires a semiconductor to absorb light and generate electron-hole pairs, and a catalyst to enhance the kinetics of electron transfer between the semiconductor and solution. A crucial question is how this catalyst affects the band bending in the semiconductor, and, therefore, the photovoltage of the cell. We introduce a simple and inexpensive electrodeposition method to produce an efficient n-Si/SiOx/Co/CoOOH photoanode for the photoelectrochemical oxidation of water to oxygen. The photoanode functions as a solid-state, metal-insulator-semiconductor photovoltaic cell with spatially non-uniform barrier heights in series with a low overpotential water-splitting electrochemical cell. The barrier height is a function of the Co coverage; it increases from 0.74 eV for a thick, continuous film to 0.91 eV for a thin, inhomogeneous film that has not reached coalescence. The larger barrier height leads to a 360 mV photovoltage enhancement relative to a solid-state Schottky barrier.

Nature Materials (2015) doi:10.1038/nmat4408
Received 15 May 2014 Accepted 27 August 2015 Published online 14 September 2015

http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4408.html

用光电化学法裂解水制氢气和氧气需要有半导体来吸收光子产生电子-空穴对，还需要有催化剂来提高电子在从半导体向溶液中转移的动力。一个重要的问题是，催化剂如何能有效影响半导体中的能带弯曲，进而提高光生电压。 Hill 等人报道了一种简单、廉价的电化学沉积法，来制备用于光催化裂解水的高效的 n-Si/SiOx/Co/CoOOH 光阳极。这个光阳极作为一种固态、金属-绝缘体-半导体光电池，与低过电压的水裂解电化学电池串联在一起。势垒高度与 Co 的覆盖范围相关，厚膜下势垒为 0.74eV ，薄膜下势垒提升到 0.91eV 。这种更大的 势垒使得最终的光生电压提高了360mV。（新材料在线）