Solar Water Splitting by TiO₂/CdS/Co–Pi Nanowire Array Photoanode Enhanced with Co–Pi as Hole Transfer Relay and CdS as Light Absorber

Abstract

The cobalt phosphate water oxidation catalyst (Co–Pi WOC) stabilized, CdS sensitized TiO2 nanowire arrays for nonsacrificial solar water splitting are reported. In this TiO2/CdS/Co–Pi photoanode, the Co–Pi WOC acts as hole transfer relay to accelerate the surface water oxidation reaction, CdS serves as light absorber for wider solar spectra harvesting, and TiO2 matrix provides direct pathway for electron transport. This triple TiO2/CdS/Co–Pi hybrid photoanode exhibits much enhanced photocurrent density and negatively shifts in onset potential, resulting in 1.5 and 3.4 times improved photoconversion efficiency compared to the TiO2/CdS and TiO2 photoanode, respectively. More importantly, the TiO2/CdS/Co–Pi shows significantly improved photoelectrochemical stability compared to the TiO2/CdS electrode, with ≈72% of the initial photocurrent retained after 2 h irradiation. The reason for the promoted performance is discussed in detail based on electrochemical measurements. This work provides a new paradigm for designing 1D nanoframework/light absorber/WOC photoanode to simultaneously enhance light absorption, charge separation, and transport and surface water oxidation reaction for efficient and stable solar fuel production.

A Cobalt‐Based Amorphous Bifunctional Electrocatalysts for Water‐Splitting Evolved from a Single‐Source Lazulite Cobalt Phosphate

“…The energy dispersive X‐ray (EDX) spectrum (Figure S5, Supporting Information) displayed the presence of Co and P with an atomic ratio close to 1:0.7, in accordance with the inductively coupled plasma atomic emission spectroscopy (ICP‐AES) analysis (Table S1, Supporting Information). In addition, the measured Fourier‐transform infrared (FT‐IR) transmission spectrum of Co 3 (OH) 2 (HPO 4 ) 2 was also found to be consistent with literature reports (Figure S6, Supporting Information) 28c. The Brunauer–Emmett–Teller (BET) surface area of Co 3 (OH) 2 (HPO 4 ) 2 was about 5.9 m 2 g −1 .…”

“…The resulting Co II and Co III percentage distribution along with their respective satellites in the area in the Co 2p 3/2 and Co 2p 1/2 region are presented in Table S2 (Supporting Information) and the surface Co:P composition is given in Table S1 (Supporting Information). The deconvoluted spectrum of P 2p showed two signals at 132.8 and 133.6 eV corresponding to P 2p 3/2 and P 2p 1/2 confirming that all P atoms are in the oxidation state of +5 which is in accordance with other metal phosphates reported in the literature (Figure S8a, Supporting Information) 12a,28c. The O 1s spectrum could be deconvoluted into O1, O2, and O3 where the O1 peak at 530.9 eV belongs to the PO bond that is characteristic for the PO 4 3− group.…”

Enhanced photoelectrochemical performance of quantum dot-sensitized TiO 2 nanotube arrays with Al 2 O 3 overcoating by atomic layer deposition

“…2b, after ALD overcoating of 30 cycles of the Al 2 O 3 overlayer, the efficiency reaches 3.35% at À0.53 V vs. SCE, corresponding to 48 fold and 1.7 fold enhancement compared to the pure TiO 2 nanotube arrays (0.07% at À0.61 V vs. SCE) and the quantum dot-sensitized TiO 2 nanotube arrays (1.97% at À0.53 V vs. SCE), respectively. In comparison, the enhancements achieved herein are higher than those of the previously reported photoanodes, such as the triple TiO 2 /CdS/ Co-Pi hybrid photoanode 39 and the CdS sensitized branched TiO 2 nanoarray photoanode. 40 And the photoconversion efficiency is much higher than those of similar photoanodes in the recent reports.…”

Photoassisted Electrodeposition of Cobalt-Phosphate Cocatalyst on BiFeO3 Thin Film Photoanode for Highly Efficient Photoelectrochemical Performances of Water Oxidation

“…21,31,32 The binding energy of P 2p was located at about 133.2 eV (Figure 4b), which was ascribed to the characteristic peak of P in phosphate. 21,33 These XPS results confirmed the formation of a layer of Co-Pi on the surface of BFO thin film photoanode. 5a shows the LSV curves of the prepared BFO and Co-Pi/BFO photoanodes in dark and upon visible light irradiation.…”