Disentangling the Role of Ag‐Based Nanocorals as Efficient Cocatalyst over CuBi2O4 Photocathodes Toward Hydrogen Evolution Reaction.

CuBi2O4 is one of the most studied potential candidates for photoelectrocatalytic solar fuel generation, from H2 production, to CO2 reduction, or even N2 fixation. Hence, understanding its performance and catalytic behavior is key to use this material under real working conditions. Herein, Ag nanocorals are successfully deposited over CuBi2O4 photocathodes for enhancing its performance as a promising candidate for photoelectrocatalytic reduction reactions. An in‐depth study of this novel structure through a combination of several materials' characterization techniques, confirming the tetragonal structure and the stoichiometric proportion of the elemental components, is presented. In addition, the different charge transfer processes and catalytic mechanisms behind the performance of Ag‐decorated CuBi2O4 photocathodes are unveiled through a combination of electrochemical impedance spectroscopy and transient absorption spectroscopy. The combination of these advanced spectroscopies reveals that Ag is acts as a true catalyst, enhancing the charge extraction and decreasing the charge accumulation and the recombination at the CuBi2O4 surface, thus boosting the photocathode performance. [ABSTRACT FROM AUTHOR]