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

Abstract

Artificial photosynthesis offers a route to producing clean fuel energy. However, the large thermodynamic requirement for water splitting along with the corresponding sluggish kinetics for the oxygen evolution reaction (OER) limits its current practical application. Here, we offer an alternative approach by replacing the OER with the glycerol oxidation reaction (GOR) for value-added chemicals. By using a Si photoanode, a low GOR onset potential of −0.05 V vs RHE and a photocurrent density of 10 mA/cm 2 at 0.5 V vs RHE can be reached. Coupled with a Si nanowire photocathode for the hydrogen evolution reaction (HER), the integrated system yields a high photocurrent density of 6 mA/cm 2 with no applied bias under 1 sun illumination and can run for over 4 days under diurnal illumination. The demonstration of the GOR-HER integrated system provides a framework for designing bias-free photoelectrochemical devices at appreciable currents and establishes a facile approach to artificial photosynthesis.

In situ and operando Raman spectroscopy of semiconducting photoelectrodes and devices for photoelectrochemistry

“…Solardriven biomass reforming offers a potential solution to replace the sluggish oxygen evolution reaction at photoanode with the more favorable organic molecule oxidation due to lower kinetic overpotentials and increased contact selectivity for minority carriers (i.e. holes) [77][78][79]. The data were obtained using the flow cell described in detail in the 'State of the art of operando RS of semiconducting photoelectrodes and devices for photoelectrochemistry' section at a flow rate of 10 ml min −1 .…”

“…It is noticeable that the addition of glycerol decreases the onset of the anodic potential and increases the photocurrent and the overall fill factor due to the drastic reduction of the kinetic overpotentials required to oxidize glycerol compared to water [77][78][79] and for the increased extraction rate of holes, respectively. This is well-documented by fixing the electrode potential (∆E WE-RE ) at +1.23 V vs. RHE for both solutions.…”

Modulation of charge-transfer behavior via adaptive interface treatment for efficient photoelectrochemical water splitting

“…Solar-driven photoelectrochemical (PEC) water splitting has been broadly regarded as a promising solution for sustainable and decarbonized technology in the quest of green and renewable energy. 1–7 Since TiO 2 photoanodes, researched by Fujishima and Honda, 8,9 were employed to perform water splitting to produce hydrogen, a majority of semiconductors, for example, TiO 2 , 10 α-Fe 2 O 3 , 11–14 Ta 3 N 5 , 15,16 and BiVO 4 , 17–22 have been regarded as ideal photoanodes for PEC water splitting in recent years. Among various candidates, BiVO 4 is the most promising candidate for PEC water oxidation because of a low bandgap (2.4 eV), low cost, and ideal band-edge positions.…”

Modeling diurnal and annual ethylene generation from solar-driven electrochemical CO2 reduction devices

“…13,22 Successfully translating bench-scale solar fuels experiments to the development of pilot-scale plants will require careful, intentional co-design of the electrocatalyst and photovoltaic for the environmental conditions of a specific deployment location. Recent work has begun to address this challenge, focusing on solar-driven hydrogen evolution [23][24][25][26][27] and solar-driven CO 2 R under conditions of variable irradiation. [28][29][30][31][32][33] However, there remains a need to develop tools 34 that aid in the understanding and prediction of transient, diurnal performance of integrated solar-fuels devices for complex, multi-product electrochemical reactions and the consequences of environmental conditions on the large-scale feasibility of these devices.…”