Inverse Opal CuBi<sub>2</sub>O<sub>4</sub> Photocathodes for Robust Photoelectrochemical Water Splitting
D. Amaranatha Reddy, Yujin Kim, Pooja Varma, Madhusudana Gopannagari, K. Arun Joshi Reddy, Da Hong, Inae Song, D. Praveen Kumar, Tae Kyu Kim
Abstract
In general, p-type CuBi2O4 (CBO) photocathodes demonstrate excellent solar-to-hydrogen conversion efficiencies but have low quantum yields near the band-edge region (i.e., above 600 nm), which substantially impedes achieving photocurrent densities that match the theoretical values. This is the main obstacle in the construction of photoelectrochemical (PEC) water-splitting cells. To overcome this difficulty, we fabricated inverse opal-like structured CBO (IO-CBO) photocathodes using a layered self-assembly approach. The fabricated photocathodes have an interconnected macroporous structure that supports enhanced visible-light-harvesting capabilities and improves intrinsic charge-carrier transport properties. Optimized IO-CBO cathodes exhibit a high photocurrent density of 2.95 mA cm–2 at 0.6 V versus a reversible hydrogen electrode with stability over 2 h of operation. Furthermore, IO-CBO cathodes have exceptional near-band-edge photon harvesting and quantum yields of 15% at 600 nm, which is unprecedented for CuBi2O4-type photocathodes. We believe that the present work promotes the application of ternary-based nanostructures in solar-driven hydrogen production.