Abstract: Since the water oxidation half-reaction requires the transfer of multi-electrons and the formation of O-O bond, it’s crucial to investigate the catalytic behaviours of semiconductor photoanodes. In this work, a bio-inspired copper-bipyridine catalyst of Cu(dcbpy) is decorated on the nanoporous Si photoanode (black Si, b -Si). Under AM1.5G illumination, the b -Si/Cu(dcbpy) photoanode exhibits a high photocurrent density of 6.31 mA cm -2 at 1.5 V RHE at pH 11.0, which is dramatically improved from the b -Si photoanode (1.03 mA cm -2 ) and f -Si photoanode (0.0087 mA cm -2 ). Mechanism studies demonstrate that b -Si/Cu(dcbpy) has improved light-harvesting, interfacial charge-transfer, and surface area for water splitting. More interestingly, b-Si/Cu(dcbpy) exhibits a pH-dependent water oxidation behaviour with a minimum Tafel slope of 241 mV/dec and the lowest overpotential of 0.19 V at pH 11.0, which is due to the monomer/dimer equilibrium of copper catalyst. At pH ~11, the formation of dimeric hydroxyl-complex could form O-O bond through a redox isomerization (RI) mechanism, which decreases the required potential for water oxidation. This in-depth understanding of pH-dependent water oxidation catalyst brings insights into the design of dimer water oxidation catalysts and efficient photoanodes for solar energy conversion.

J.-X. Jian*, J.-X. Liao, M.-H. Zhou, M.-M. Yao, Y.-J. Chen, X.-W. Liang, C.-P. Liu, Q.-X. Tong*, Enhanced Photoelectrochemical Water Splitting of Black Silicon Photoanode by pH-Dependent Copper-Bipyridine Catalysts, Chem. Eur. J., 2022, DOI: 10.1002/chem.202201520. (中科院二区, IF = 5.020)

https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202201520