Rationally Designed Heterojunction on a CuBi₂O₄ Photocathode for Improved Activity and Stability during Photoelectrochemical Water Reduction

Abstract

CuBi2O4 (CBO) is a promising photocathode for photoelectrochemical (PEC) water reduction, whereas the disadvantages of poor stability and severe charge recombination still hinder its application. In response, we designed a stabilized, efficient CBO/ZnSe/P25 (CBO/ZS/P25) photocathode with the CBO film modified by ZS and P25. As a result, this novel photocathode exhibited an outstanding current density of 0.43 mA/cm2, more than twice that of CBO. Systematic studies reveal that the high performance is attributed to heterojunction formation between ZS and P25, high electron mobility of ZS and hole extraction capacity of CBO. Besides, P25 protective layer can effectively blocks contact with the electrolyte and enhance the stability (retained nearly 90 % of the photocurrent after testing 5000s). Therefore, our results can provide an efficient strategy to design high performance CBO‐based photocathode material.

Dendritic CuBi2O4 Array Photocathode Coated with Conformal TiO2 Protection Layer for Efficient and Stable Photoelectrochemical Hydrogen Evolution Reaction

“…The photostability of the TiO 2 -protected CuBi 2 O 4 dendrites in neutral and alkaline solutions was evaluated in contrast with the bare CuBi 2 O 4 dendrites under 100.0 mW cm –2 illumination, and the results are shown in Figure c,d (under constant illumination) and Figure S14 (under chopped illumination). As the CuBi 2 O 4 photocathode exhibits highly positive onset potential toward the HER, the stability measurements reported in the literature were usually performed using chronoamperometry at a relatively high potential of 0.40 V vs RHE in neutral solution ,, and even 0.600 V vs RHE (or higher) in alkaline solution. ,,,, Accordingly, for the sake of easy comparison, we carried out our stability experiments by applying a constant potential of 0.400 V vs RHE in neutral solution and 0.600 V vs RHE in alkaline solution. As shown in Figure c, the bare CuBi 2 O 4 dendritic photocathode shows a clear decay in photocurrent density in neutral solution within the time duration of the PEC HER, whereas the CuBi 2 O 4 /TiO 2 composite exhibits a stable photocurrent density of ca.…”

“…Our CuBi 2 O 4 dendrites exhibit a photocurrent density of 0.83 mA cm −2 at 0.200 V vs RHE, which is among the highest values ever reported for CuBi 2 O 4 photocathodes at the same applied potential (also see Table S1). 8,[14][15][16]18,19,27,34,35,49,50 Meanwhile, as shown in Figure 4a, the chopped photocurrent shows transient spikes, which are commonly observed on the CuBi 2 O 4 and copper oxides photocathodes in the negative potential region. 19,51 These spikes are mainly caused by the sluggish electron transfer kinetics from CuBi 2 O 4 to H 2 O across the CuBi 2 O 4 /solution interface, which results in the accumulation of photoinduced electron and then leads to a high recombination rate.…”

“…To assess the effect of the TiO 2 layer on the light absorption, we examined the UV−vis absorption spectra of the CuBi 2 O 4 dendrites before and after deposition of TiO 2 layer (see Figure S12) and found that the protective layer indeed decreased the light absorption. As a thicker TiO 2 layer results in better protection of CuBi 2 O 4 and also leads to a lower light absorption efficiency, there must be a maximum thickness at which the TiO 2 layer does not significantly 30 the stability measurements reported in the literature were usually performed using chronoamperometry at a relatively high potential of 0.40 V vs RHE in neutral solution 19,34,49 and even 0.600 V vs RHE (or higher) in alkaline solution. 17,29,30,36,37 Accordingly, for the sake of easy comparison, we carried out our stability experiments by applying a constant potential of 0.400 V vs RHE in neutral solution and 0.600 V vs RHE in alkaline solution.…”

Augmented photoelectrochemical water reduction: influence of copper vacancies and hole-transport layer on CuBi2O4 photocathode

“…6(c) and S6). † According to the recent reports, 29,31,64,65 the CBM of a typical CBO photocathode (CBO-Air) is located close to WF of the back contact electrode (i.e., the FTO substrate); thus, there are more charge recombinations at the back interface. The band alignment between the CBO photocathodes and back contacts aer the E F equilibrium has been reached and is schematically illustrated in Fig.…”

Enhanced photoelectrochemical performance of LaFeO3 photocathode with Au buffer layer

“…[1][2][3][4][5][6] Among the numerous PEC materials, p-type semiconductors are one of the best photocathodic materials because of their good PEC performance. 7,8 Recently, many common p-type materials such as p-Cu 2 O, 9-11 p-NiO, 12,13 p-CuFeO 2 14 and p-CuBi 2 -O 4 [15][16][17] have been developed for PEC water splitting applications. Specically, Luo et al fabricated Cu 2 O nanowire array photocathodes with a durable protective overlayer which improved the stability of Cu 2 O, thus delivering high photocurrent densities and stable operation.…”