59 / 2019-10-14 11:51:38

DEVELOPING EFFICIENT TERNARY OXIDE PHOTOANODES WITH LONG-TERM STABILITY FOR PRACTICAL SOLAR WATER SPLITTING

Solar water splitting,Photoanode,Ternary oxide,Long-term stability

Solar hydrogen production by photoelectrochemical (PEC) water splitting offers a great means to address the intermittency and storage problem of solar energy. However, photoanodic materials operable in the low-bias range, i.e., between 0.2~0.7 Vvs RHE, under visible light illumination are limited, but are essential for building practical non-biased PEC overall water splitting devices.
So far, most reports with such low-bias performance are based on n type BiVO4 semiconductor. Although the photocurrents have been significantly improved in recent years, the long-term stability is still a challenge. Furthermore, limited visible light absorption restricts the maximum solar conversion efficiency. Sn(II)-based oxide materials are potential candidates to deliver better light absorption along with charge separation efficiency comparable to BiVO4. But the stability of Sn(II) ion is the top concern in view of the oxidative environment during operation.
In this talk, we show that new concepts of surface modification of BiVO4 and SnNb2O6 can enable efficient water oxidation below 0.6 V vs RHE with unprecedented stability. To address the PEC corrosion and catalyst consumption for BiVO4, we developed a combined doping-annealing process to improve its crystallinity to suppress dissolution and an in-situ self-generation and regeneration process to maintain the catalytic activity. Bare SnNb2O6 electrodes indeed suffer from rapid degradation. As conventional methods for catalyst decoration do not work well with the current system, we have developed a unique method for catalyst deposition and activation to avoid corrosion of Sn(II) during the operations. We have also studied the underlying mechanism for the stabilization, and the discrete roles of Co-based layer and Ni-based layer in this process are successfully identified.