This work demonstrates a strategic nanoengineering design of a TiO2 nanorod (NR)-based photoanode. Here, the doping of Sb in TiO2 NRs along with co-integration of plasmonic gold nanoparticles and an amorphous lanthanum-cobalt double hydroxide (LaCo­(OH) x ) oxygen evolution catalyst (OEC) is found to improve visible-light absorption, rapid electron–hole pair separation, fast electron transportation, and the surface photocatalytic reaction of the photoanode, resulting in the ameliorated water oxidation performance. The Sb-doped TiO2 NRs exhibit a reduced band gap, improved photoconductivity, and an excellent photocurrent density (1.03 mA·cm–2 at 1.23 V vs reversible hydrogen electrode (RHE)). The anchoring of Au nanoparticles on Sb-TiO2 NRs significantly improves visible-light absorption and the photocurrent density because of the localized surface plasmon resonance effect. Herein, LaCo­(OH) x is demonstrated as a photo-electrocatalyst and incorporated with a TiO2 NR-based photoanode for the first time. Integration of a suitable amount of the LaCo­(OH) x OEC with Au/Sb-TiO2 NRs significantly improves photocarrier separation, photogenerated charge transportation, and the surface photo-electrocatalytic reaction and reduces the charge transfer resistance, delivering above 10 mA/cm2 photocurrent density at 2.06 V vs RHE and resulting in the enhanced photoelectrochemical (PEC) activity and photostability for water oxidation. The LaCo­(OH) x -electrodeposited Au/Sb-TiO2 NR sample exhibits a hydrogen production rate of 21.4 μmol·cm–2·h–1 at the counter electrode under illumination. This work demonstrates a strategic design of a TiO2-based photoanode integrating doping with plasmonic nanostructures and cocatalysts for solar fuel production through water splitting.

The architectural design of multidimensional nanoheterostructures-based photoelectrodes is demonstrated by coupling the multilayered two-dimensional (2D) structure of MoS 2 and MoO 3 on the well-aligned arrays of one-dimensional (1D) ZnO nanorods template, with the expected effective synergic effects. The advantages of catalytically active sites of the 2D layered structure of transition-metal dichalcogenides/oxides is integrated with the distinctive dimensionality-dependent phenomena of 1D structure to achieve enormous surface area for light harvesting and photoelectrochemical reaction, along with the favorable photocarrier dynamics required for water splitting. The ZnO/MoS 2 and ZnO/MoO 3 nanoheterostructure photoanodes exhibit low onset potential and enhanced broadband light absorption, resulting in high photocurrent densities of 2.04 and 0.67 mA cm −2 at 1.23 V versus reversible hydrogen electrode under AM 1.5 G illumination, which corrospond to 334% and 43% increases in photocurrent, respectively, compared to that of pure ZnO nanorods. The nanoheterostructure photoanodes also exhibit enhanced applied bias photon-to-current conversion efficiency and superior spatial photo-induced exciton separation and transportation, because of the favorable interfacial band alignment at 2D−1D nanoheterointerfaces, and suppress the surface charge recombination, which promotes hole transportation at the nanoheterostructure/electrolyte interface and boost the surface oxygen evolution reaction, leading to enhanced photoelectrochemical performance.

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This work demonstrates the photoelectrochemical (PEC) water splitting activity of a one-dimensional n-ZnO/p-ZnCo2O4 nanoheterojunction photoanode synthesized by using the chemical bath deposition and electrodeposition methods. The nanoheterojunction photoanode exhibits an improved solar light-harvesting performance. The type-II analogous band alignment occurs because of p–n junction formation between p-ZnCo2O4 and n-ZnO nanorods (NRs), which accelerates the charge separation and transfer, significantly reducing the photogenerated electron–hole pair recombination. The ZnCo2O4 surface overlayer also passivates the surface states in ZnO, resulting in a remarkable reduction in photocarrier recombination. Additionally, the p-ZnCo2O4 shell layer acts as the oxygen evolution reaction (OER) catalyst to influence the PEC reactions at the electrode/electrolyte interface, boosting the charge transfer process and water oxidation reaction kinetics. Overall, an innovative nanoheterojunction photoanode is constructed to improve the PEC water oxidation of ZnO NRs by incorporating p-ZnCo2O4, which acts both as an OER catalyst and a p-type light-harvesting semiconductor.

Severe surface photocarrier recombination and poor electronic conductivity are the major factors behind the sluggish photoelectrochemical water oxidation kinetics of the ZnFe2O4 photoanode. Here, the CeOx catalyst overlayer has been coupled with the reduced ZnFe2O4 nanorods (NRs) to reduce the surface charge recombination on the photoanode significantly. The density functional theory (DFT) studies indicate that the oxygen vacancy defect‐rich CeOx catalyst constructs a favorable band alignment with ZnFe2O4 promoting rapid photocarrier separation and serves as a conducting photocarrier transfer pathway accelerating the hole transportation toward the electrode/electrolyte interface. The ZnFe2O4/CeOx nano‐heterostructure photoanode exhibits a current density of 0.64 mA cm−2 at 1.23 V versus RHE under AM 1.5 G illumination, which corresponds to >167% increase over that of the ZnFe2O4 NRs photoanode. The CeOx coupling reduces the onset potential cathodically by 180 mV over the ZnFe2O4 NRs photoanode. The ZnFe2O4/CeOx nano‐heterostructure photoanode also exhibits excellent charge transfer efficiency (≈64% at 1.23 V vs RHE) and photostability. The results indicate the superior catalytic performance of oxygen vacancy defect‐rich CeOx in the PEC process. This work demonstrates the multifunctional role of CeOx as a surface passivation overlayer, hole transfer layer, and efficient oxygen evolution reaction catalyst.