| Converting sunlight directly into chemical energy to achieve photoelectrochemical water splitting hydrogen production by semiconductors is one of the most effective ways to alleviate the problem of current environmental pollution and energy crisis.This has become an issue in research now.The key to achieve efficient photoelectrocatalytic water splitting is the efficient and stable semiconductor photoelectrode materials.Researchers have conducted various research and modification on semiconductor electrode materials,and a series of research achievements have been got as result of the exploration in this field.The response range of visible light,separation efficiency of photogenerated electron hole pair,reaction kinetics,stability,etc.are still important factors which restricting the photoelectrode to achieve high conversion efficiency.CaBixOy is widely used in the photocatalysis due to its visible light response,high photocatalytic efficiency and good stability,but it has been rarely reported in the photoelectrocatalysis.In this paper,two kinds of Ca Bix Oy thin films were prepared on FTO glasses substrates by hydrothermal and spin coating method,and used as photoanode for photoelectrochemical water splitting.The process of chemical reaction and the mechanism of film formation in the process of film synthesis were analyzed.The influence of p H,hydrothermal time and other parameters on the morphology of Ca Bix Oy was studied.The influence of morphology,thicknes on the photoelectrochemical properties of the film was discussed.In addition,based on the good light-absorbing properties and carrier transport properties of thick Ca Bi6O10 NPs,a narrow bandgap Cu2 O was deposited on the Ca Bi6O10 to form heterojunction,the influence mechanism of the heterojunction on the photoelectrochemical properties is studied,and the carrier separation and transport mechanism in the heterogeneity was analyzed.The photoelectrode is further modified by Ni OOH,and the influence on thermodynamics of water oxidation reaction is analyzed.The results show that Ca Bi2O4 films with different morphology were prepared by controlling the hydrothermal time.The dumbbell-shaped Ca Bi2O4 prepared at 180 °C for 12 h obtain the maximum photocurrent density 0.26 m A/cm2 at 1.23 V vs.RHE.Ca Bi6O10 films with different morphology and thickness are prepared by adjusting the p H of precursor solution and spin coating times.The thick Ca Bi6O10 NPs with thickness of 300 nm obtain the maximum photocurrent density of 0.39 m A/cm2,which was attributable to the increase of light absorbance and separating efficiency of photogenerated charge carriers caused by the thick nanoplate structure.The thick Ca Bi6O10 NPs is modified with Cu2 O to form heterojunctions,which broadened the photoresponse range and promoted the separation and transport of photogenerated electron hole pair.The photocurrent density is up to 1.31 m A/cm2 at 1.23 V vs.RHE,which is 3.3 times of the simple Ca Bi6O10 samples.The Ca Bi6O10/Cu2 O photoelectrode is further modified by Ni OOH cocatalyst to decrease the recombination of photogenerated electron-hole pair and achieve a rapid water oxidation reaction.The photocurrent density of the obtained ternary Ca Bi6O10/Cu2O/Ni OOH photoelectrode increased to 1.89 m A/cm2 at 1.23 V vs.RHE,which is 4.8 times of the simple Ca Bi6O10 photoelectrode.In addition,the onset potential is negatively shifted from 0.123 V vs.RHE to 0.027 vs.RHE.At the same time,the Ni OOH acts as a holes scavenger,it inhibits the oxidative reaction of Cu2 O by photogenerated holes.The stability of Ca Bi6O10/Cu2O/Ni OOH is significantly improved compared to Ca Bi6O10/Cu2 O.After 2 h continuous illumination,the photocurrent density of Ca Bi6O10/Cu2O/Ni OOH photoelectrode still maintains 89 % of the initial photocurrent density. |
