Yb3+, Er3+ co-doped NaGdF4/BiVO4 embedded Cu2O photocathodes for photoelectrochemical water reduction with near infrared light

Upconverting near infrared light to photoelectrode absorbable visible light is desirable for enhancing photo electrochemical hydrogen production. In this work, photocathodes were fabricated by embedding beta-NaGdF4: Yb3+,Er3+ nanocrystals and BiVO4 microcrystals into Cu2O matrix, where beta-NaGdF4:Yb3+, Er3+ nanocrystals were used for upconversion luminescence and the BiVO4 microcrystals were employed to form abundant heterojunctions inside the Cu2O matrix. In comparison with the pristine Cu2O thin film, the NaGdF4:Yb3+,Er3+/BiVO4 embedded Cu2O photocathodes illustrated good response to near infrared light. Photocurrent produced by 980 nm light was enhanced by a factor of 40 to about 1 mA cm(-2). The high photocurrent can be attributed to the widely distributed internal electric fields introduced by the BiVO4 in the bulk of the Cu2O, which inhibits the recombination of the electrons and holes excited by the NaGdF4:Yb3+,Er3+ emitted visible light in the vicinity. Furthermore, the 980 nm light induced temperature increment exhibits significant synergistic effect on the enhanced photocurrent.