Synergistic Use of a Solid Solution and a Cocatalyst on Co_xCd_1–xS/Ni_yFe_1–y-LDH for Efficient and Stable Photoelectrochemical Performance

Abstract

Cadmium sulfide (CdS)-based photoelectrodes have been extensively studied in photoelectrochemical (PEC) water splitting, but these semiconductors still suffer from low photogenerated carrier separation efficiency and poor photostability. Herein, we synthesized and explored a Co x Cd1–x S/Ni y Fe1–y -LDH composite photoanode composed of a Co x Cd1–x S solid solution and a Ni y Fe1–y -LDH cocatalyst. Compared with the pristine CdS film, the synthesized Co0.30Cd0.70S/Ni0.50Fe0.50-LDH composite film has optimum PEC activity and photostability in the process of water oxidation due to the synergism of the solid solution and the cocatalyst. First, the Co0.30Cd0.70S solid solution doped with an appropriate amount of Co2+ can not only effectively absorb photons but also maximize the utilization of photons, thereby improving the PEC performance. Second, Ni0.50Fe0.50-LDH in the outer layer of the Co0.30Cd0.70S/Ni0.50Fe0.50-LDH photoanode promotes the reaction kinetics of surface oxygen production of Co0.30Cd0.70S, which further improves the carrier density and the separation efficiency of photogenerated carriers. Meanwhile, the Ni0.50Fe0.50-LDH cocatalyst quickly captures and transports photogenerated holes to promote the photocorrosion resistance of Co0.30Cd0.70S. This study provides a path to synthesize the highly efficient and stable CdS-based photoanode by the synergistic use of a solid solution and a cocatalyst for PEC water splitting.

Enhanced Electrocatalytic Water Oxidation by Interfacial Phase Transition and Photothermal Effect in Multiply Heterostructured Co9S8/Co3S4/Cu2S Nanohybrids

“…To get some insight onto the obvious differences in electrocatalytic performances between different catalysts, we performed some control experiments. Figure 3e displays the Mott–Schottky curves of these catalysts, based on which the charge carrier density of the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs, Co 9 S 8 and Cu 2 S were determined to be 2.09*10 15 cm −3 , 7.76*10 14 cm −3 and 3.71*10 14 cm −3 , respectively, indicative of increased charge carrier density inside the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs, which is beneficial to rapid carrier transfer [50,51] . Figure S19 shows the electrochemical impedance spectra (EIS) of these catalysts, and the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs present an interface charge transfer resistance ( R ct ) value of 11.6 Ω, obviously smaller than that of the Co 9 S 8 (23.9 Ω) and Cu 2 S (620.3 Ω), confirming the rapid interface electron transfer dynamics of the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs.…”

“…Figure 3e displays the Mott-Schottky curves of these catalysts, based on which the charge carrier density of the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs, Co 9 S 8 and Cu 2 S were determined to be 2.09*10 15 cm À 3 , 7.76*10 14 cm À 3 and 3.71*10 14 cm À 3 , respectively, indicative of increased charge carrier density inside the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs, which is beneficial to rapid carrier transfer. [50,51] Figure S19 shows the electrochemical impedance spectra (EIS) of these catalysts, and the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs present an interface charge transfer resistance (R ct ) value of 11.6 Ω, obviously smaller than that of the Co 9 S 8 (23.9 Ω) and Cu 2 S (620.3 Ω), confirming the rapid interface electron transfer dynamics of the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs. Additionally, electrochemical double-layer capacitance (C dl ) tests uncover that the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs possess larger C dl value (13.5 mF cm À 2 ) than that of the Co 9 S 8 (5.8 mF cm À 2 ) and Cu 2 S (0.09 mF cm À 2 ), implying more electrochemical active sites for the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs (Figure 3f and Figure S20).…”

Enhanced Electrocatalytic Water Oxidation by Interfacial Phase Transition and Photothermal Effect in Multiply Heterostructured Co9S8/Co3S4/Cu2S Nanohybrids

“…Figure 3e displays the Mott-Schottky curves of these catalysts, based on which the charge carrier density of the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs, Co 9 S 8 and Cu 2 S were determined to be 2.09*10 15 cm À 3 , 7.76*10 14 cm À 3 and 3.71*10 14 cm À 3 , respectively, indicative of increased charge carrier density inside the Co 9 S 8 /Co 3 S 4 /Cu 2 S NHs, which is beneficial to rapid carrier transfer. [50,51] Figure S19 shows the electrochemical impedance spectra (EIS) of these catalysts, and the Co 4c). However, the overpotential that from *O to *OOH step is 11 % higher than that over the Co(6-1) site on Co 3 S 4 (311).…”

Bridging electrocatalyst and cocatalyst studies for solar hydrogen production via water splitting

“…102 A solvothermal method can also be applied to grow metal (hydr)oxide or sulphide CCs directly on a PC. 103–107 The straightforward addition of the PC into the EC synthesis solution can generate a CC/PC composite.…”