Many technological approaches have been searched in order to overcome the main challenges concerning the world energy crisis and global environmental issues. Among them, plasmon‐driven photoelectrochemical reactions towards water electrolysis attract great attention due to their capacity to efficiently harvest solar energy. Synergism between tunable optical features and catalysts active sites of plasmonic nanomaterials gives rise to a singular perspective for photochemical processes. Through resonant photonic excitation, hot carriers’ motion facilitates the charge transfer process on the catalyst surface for chemical reactions. In this minireview, recent experimental research with emphasis on water splitting reactions have been summarized with the purpose of understanding the mechanistic hot electrons generation and transfer on the plasmonic noble metal nanoparticles (MNPs) and transition metal oxides (MOs) heterostructures. Examples of plasmonic nanomaterials are highlighted and compared for both water electrolysis semi reactions. Finally, this work concludes by describing the remaining challenges and gives some perspectives regarding the promising future of plasmon‐driven reactions investigations.

MnO2 is a cheap and versatile material, being able to act as a catalyst for different electrochemical reactions. The addition of small amounts of Au nanoparticles (NPs) enables the possibility to explore the localized surface plasmon resonance (LSPR) effect to improve the photocatalytic properties of MnO2. The LSPR effect can accelerate several reactions under visible light irradiation, improving the charge separation and light harvesting properties of semiconductors. Here, by employing MnO2 nanowires decorated with Au NPs (MnO2–Au), we demonstrated that MnO2 catalytic activity can be greatly improved by the LSPR in a hybrid system. The catalytic properties of the semiconductor were demonstrated for the H2O2 oxidation as a model reaction. A clear increase in the current of H2O2 oxidation was verified for gold decorated nanowires under visible light irradiation, with an increase of 116% in the sensitivity compared with dark conditions. Mechanistic analysis indicates that the increased performance was related to a more efficient charge separation by plasmonic generated hot electrons and holes. Moreover, we demonstrated that the thermal effect had no significant contribution to the increase in activity observed, as it was verified no expressive increase in temperature under light irradiation with a thermal camera. We believe the results reported herein provide an approach to achieve improved light harvesting and performance in the visible range of the spectrum for semiconductors, inspiring the use of plasmonic heterostructures toward electrocatalysis.

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