Approaching Theoretical Limit of Ta3N5 Photoanode via Photothermal‐Accelerating Kinetics with Full‐Spectrum Utilization

Tantalum nitride is widely considered as a promising photoanode material for its suitable band structure as well as the high theoretical conversion efficiency in solar water splitting. However, it is limited to inefficient photoinduced electron–hole pair separation and interfacial dynamics in the photoelectrochemical oxygen evolution reaction. Herein, multiple layers including Ti x Si y and NiFeCoO x were fabricated based on band engineering to regulate tandem electric states for efficient transfer of energy carriers. Besides, photothermal local surface plasmon resonance was introduced to accelerate the kinetics of photoelectrochemical reactions at the interface when the special Ag nanoparticles were loaded to extend the absorbance to near infrared light. Consequently, a recordable photocurrent density of 12.73 mA cm −2 has been achieved at 1.23 V versus RHE, approaching a theoretical limit of the tantalum nitride photoanode with full‐spectrum solar utilization. Meanwhile, compared to the applied bias photon‐to‐current efficiency of 1.36% without photothermal factor, a high applied bias photon‐to‐current efficiency of 2.27% could be raised by applying local surface plasmon resonance to photoelectrochemical oxygen evolution reaction. The efficient design could maximize the use of solar light via the classification of spectrum and, therefore, may spark more innovative ideas for the future design and development of the next‐generation photoelectrode.