Metal oxide semiconductors are promising candidate photoelectrodes for photoelectrochemical H2O2 production if the issue of poor efficiency and selectivity can be resolved. An unfavorable charge transport barrier causes poor carrier...

Solar–fuel conversion depends on effective collection of photocarriers in the photoelectrode. In practice, however, considerable photocarriers are lost in the bulk through recombination due to the absence of a driving force. To overcome this, herein, a full-space electric field is induced in BiFeO3 photocathodes by building a gradient homojunction through Fermi level engineering. As expected, the BiFeO3 photocathodes with forward electric field show significantly enhanced performance: a state-of-the-art photocurrent of −1.02 mA·cm–2 at 0.5 V vs RHE and H2O2 production of 380 mmol·(L·m2)−1 within 50 min. First-principles calculations and experimental analysis suggest that the Bi vacancies as shallow acceptors can significantly modulate the Fermi level of BiFeO3. The resulting internal electric field serves as an additional driving force to promote charge collection. This work provides an approach to induce a full-space electric field in semiconductor films through gradient defects modulation, which can be broadly applied to other optoelectronic systems.

Transition metal oxide semiconductors are important candidates for photoelectrodes to convert solar energy to fuels. However, the practical applications of these materials are hindered by severe carrier losses and sluggish...

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Charge transport mediators are commonly used in photoelectronic devices to promote selective charge transport and mitigate carrier losses. However, related investigations are mainly carried out by the trial‐and‐error method, and a deeper understanding of its local charge transport behavior is still lacking. Herein, a comprehensive study is performed on a BiVO4/Ti3C2 photoanode to reveal its local charge transport properties by combing microprobe technologies and numerical computations. For the first time, a nano‐Schottky junction is directly shown at the BiVO4/Ti3C2 interface and the band bending is quantified with promoted hole transport and prolonged photocarrier's lifetime. These mechanistic insights leverage a path to further optimize performance through interface engineering and achieve a photocurrent of 5.38 mA cm−2 at 1.23 V versus reversible hydrogen electrode. This work provides deeper insight into the function of charge transport mediators in view of interface contact rather than material nature and demonstrates a strategy to improve photoelectrochemical performance through Fermi‐level engineering.