Here, we discuss the application, advantages, and potential pitfalls of using transient UV/Vis (ultraviolet-visible) absorption spectroscopy to study photoelectrodes for water splitting. We revisit one of the most commonly studied water oxidation photoanodes (α-Fe2O3−x) to provide commentary and guidelines on experiment design and data analysis for transient absorption (TA) studies of photoelectrodes within a photoelectrochemical cell. We also assess the applicability of such in situ TA studies to understand photoelectrodes under operating conditions. A major limitation is that most, if not all, past in situ TA studies have been carried out using only pulsed light sources to generate carriers, with the electrode held in the dark at other times, which is shown to be a poor model for operating conditions. However, with a simple modification of existing TA experiments, a simple operando TA measurement is reported.

Solar-driven CO2 reduction for the production of fuels and chemicals is a promising technology for achieving carbon neutrality. Photocatalytic CO2 reduction, photoelectrochemical CO2 reduction and photovoltaic-electrochemical CO2 reduction, are three...

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Photoelectrochemical water splitting is a promising strategy for harvesting and converting solar energy to green hydrogen energy. However, the current inferior performance restricts further improvement of the solar-to-hydrogen efficiency. In this work, a molecular catalyst [NdCo3(btp-3H)2(Ac)2(NO3)2] (NO3)·2H2O (referred to as NdCo3 herein) was deposited onto a porous BiVO4 photoanode using a drop-casting method, and the molecular catalyst was held in place on the BiVO4 surface via intermolecular forces. The photoelectrochemical water oxidation performance of the BiVO4/NdCo3 photoanode reached 2.25 mA cm–2 at 1.23 V vs RHE under AM 1.5G illumination (100 mW cm–2), which was much higher than the pristine BiVO4 photoanode (1.49 mA cm–2). The enhanced performance could be attributed to the improvement of the charge carrier transfer efficiency, resulting in the acceleration of the water oxidation kinetics and inhibiting charge carrier recombination. In addition, the electrocatalytic properties of the homogeneous system were also studied. It was found that a heterogeneous catalytic film was formed due to the water solubility of NdCo3, which enabled a long electrolysis process to be maintained. The electrocatalytic performance of a homogeneous system reached 1 mA cm–2 at 2.31 V vs RHE and was different from the heterogeneous catalytic film (reached 1 mA cm–2 at 2.10 V vs RHE). This integrated system showed that the combination of a molecular catalyst with a photoelectrode helped to promote charge-carrier transport and separation, reducing the amount of charge-carrier recombination. Our approach may be applicable to other materials, helping to provide ideas for developing material combinations capable of achieving greater solar-to-hydrogen efficiencies.