The significant progress of the PECHouse3 project includes the advancement of Cu2O photocathodes, exploration of new p-type Cu2S materials, modelling of optoelectronic processes, and demonstration of a variety of tandem configurations for standalone sunlight-driven water splitting.
The photoelectrochemical (PEC) performance of Cu2O photocathodes was boosted to 10 mA cm-2 at 0 V versus reversible hydrogen electrode (RHE) with an onset potential of 1 V versus RHE by marrying the buried Cu2O/Ga2O3 heterojunction with nanowire structured electrode, which is by far the best metal oxide based photoelectrode for solar water splitting. In addition, solution processed Cu2S photocathodes were developed, achieving a photocurrent density up to 7.0 mA cm-2 at -0.3 V versus RHE under AM 1.5G simulated sunlight illumination. Optoelectronic models were created to understand and optimize photoelectrode device architectures in terms of composition, doping, and morphology.
In the end, we demonstrated two types of standalone tandem solar water splitting devices. One is composed of perovskite light harvesters, Earth-abundant catalysts and a bipolar membrane. Overall, 10 mA cm-2 current density with 1.63 V bias voltage for electrochemical water splitting and 12.7% solar to hydrogen conversion efficiency for solar driven water splitting were achieved. The second is an all oxide based tandem, composed of a Cu2O photocathode and a BiVO4 photoanode, and 3% STH conversion efficiency was achieved. Furthermore, we showed the scale up possibility using Cu2O photocathodes as an example.
