Architecture lattice‐matched cauliflower‐like CuO/ZnO p–n heterojunction toward efficient water splitting

Abstract

BACKGROUND: In photoelectrochemical (PEC) water splitting, hydrogen and oxygen can be dissociated from water molecules on semiconductors by directly utilizing clean renewable solar energy. The key bottleneck of PEC water splitting is to design new types of photoelectrodes with long-term stability and high PEC performance.RESULTS: Here, cauliflower-shaped p-n CuO/ZnO heterojunction photocathodes with lattice matching were synthesized using one-step electrodeposition and heat treatment. The results showed that the deposition of CuO and ZnO took place simultaneously. The proportion of CuO and ZnO varied with the electrodeposition time and calcination temperature and duration. The parallel lattice-matched CuO/ZnO heterojunction enhanced the separation and migration of photogenerated charge carriers, which accomplished a photocurrent density value of approximately −1.8 mA cm −2 at a bias of 0 V RHE in 0.5 mol L −1 Na 2 SO 4 solution.CONCLUSIONS: This work could provide a simplified strategy for the synthesis of p-n copper-based heterogeneous photocathodes for application in PEC water splitting.

Hierarchical CuO/ZnO Heterojunction with Improved Spectrum Absorption for Interfacial Solar Steam Generation

“…Moreover, the peaks at 31.8°(100), 34.4°(002), and 36.3°(101) were indexed to the planes of ZnO. These distinct XRD patterns in CZO–CP were in good agreement with previous reports, confirming the successful creation of the p–n CZO on the surface of CP. , …”

“…After the redistribution and equilibrium of electrons were reached, the contact interfacial region was charged. As a result, the band structures of CuO and ZnO changed and exhibited bending, which could form a built-in electric field from ZnO to CuO for improving the transformation and migration of photogenerated carriers. ,,, During the separation of photogenerated carriers in CZO, most energy could be converted into heat energy by nonradiative relaxation. ,,, As a result, CZO provided excellent solar energy conversion for photothermal energy, outperforming CuO (Figure S2). In combination with the carbon material, the CZO–CP with hierarchical structures also showed superior light absorption capacity compared to that of the CZO and CP, which had more multiple reflections to capture more photons because of hierarchical structures .…”

“…The deposition of CuO/ZnO on CP was performed using our previously reported method . Briefly, copper (Cu­(CH 3 COO) 2 , 15 mmol L –1 ) and zinc (Zn­(NO 3 ) 2 , 0.5 mol L –1 ) ions were codeposited on CP via galvanostatic electrodeposition and then calcined to obtain the copper oxide/zinc oxide heterojunction.…”

“…49−51 Previously, we reported the construction of lattice-matched CuO/ZnO heterojunctions, which can effectively separate photogenerated electron− hole pairs, thereby enhancing the nonradiative relaxation. 52 In addition, combining CuO/ZnO heterojunctions with carbon materials (e.g., carbon paper, CP) could further expand the light absorption range. 53,54 The excellent carrier mobility and wide range of light absorption could enable CuO/ZnO heterojunctions to perform the role of photothermal conversion in ISSG, resulting in higher water evaporation.…”

“…This means that it can absorb solar light in all visible and part of the near-infrared light spectrum. CuO also has several advantages, including good hydrophilicity, easy preparation, and abundant reserves, making it a popular choice for antibacterial, photocatalytic, photoelectrochemical, and solar evaporation applications. − Nevertheless, the higher photogenerated carrier recombination rate limits its occurrence of nonradiative relaxation effect, which could be improved by a promising and repeatedly reported strategy of a heterogeneous electric field in the p–n junction. − Previously, we reported the construction of lattice-matched CuO/ZnO heterojunctions, which can effectively separate photogenerated electron–hole pairs, thereby enhancing the nonradiative relaxation . In addition, combining CuO/ZnO heterojunctions with carbon materials (e.g., carbon paper, CP) could further expand the light absorption range. , The excellent carrier mobility and wide range of light absorption could enable CuO/ZnO heterojunctions to perform the role of photothermal conversion in ISSG, resulting in higher water evaporation.…”