Photochemical Diodes for Simultaneous Bias-Free Glycerol Valorization and Hydrogen Evolution

Artificial photosynthesis offers a route to producingclean fuelenergy. However, the large thermodynamic requirement for water splittingalong with the corresponding sluggish kinetics for the oxygen evolutionreaction (OER) limits its current practical application. Here, weoffer an alternative approach by replacing the OER with the glyceroloxidation reaction (GOR) for value-added chemicals. By using a Siphotoanode, a low GOR onset potential of -0.05 V vs RHE anda photocurrent density of 10 mA/cm(2) at 0.5 V vs RHE canbe reached. Coupled with a Si nanowire photocathode for the hydrogenevolution reaction (HER), the integrated system yields a high photocurrentdensity of 6 mA/cm(2) with no applied bias under 1 sun illuminationand can run for over 4 days under diurnal illumination. The demonstrationof the GOR-HER integrated system provides a framework for designingbias-free photoelectrochemical devices at appreciable currents andestablishes a facile approach to artificial photosynthesis.