Point-defect engineering of nanoporous CuBi_(2)O_(4) photocathode via rapid thermal processing for enhanced photoelectrochemical activity

Engineering point defects such as metal and oxygen vacancies play a crucial role in manipulating the electrical,optical,and catalytic properties of oxide semiconductors for solar water splitting.Herein,we synthesized nanoporous CuBi_(2)O_(4)(np-CBO)photocathodes and engineered their surface point defects via rapid thermal processing(RTP)in controlled atmospheres(O_(2),N_(2),and vacuum).We found that the O_(2)-RTP treatment of np-CBO increased the charge carrier density effectively without hampering the nanoporous morphology,which was attributed to the formation of copper vacancies(VCu).Further analyses revealed that the amounts of oxygen vacancies(Vo)and Cu^(1+)were reduced simultaneously,and the relative electrochemical active surface area increased after the O_(2)-RTP treatment.Notably,the point defects(VC_(u),Cu^(1+),and Vo)regulated np-CBO achieved a superb water-splitting photocurrent density of-1.81 m A cm^(-2) under simulated sunlight illumination,which is attributed to the enhanced charge transport and transfer properties resulting from the regulated surface point defects.Finally,the reversibility of the formation of the point defects was checked by sequential RTP treatments(O_(2)-N_(2)-O_(2)-N_(2)),demonstrating the strong dependence of photocurrent response on the RTP cycles.Conclusively,the surface point defect engineering via RTP treatment in a controlled atmosphere is a rapid and facile strategy to promote charge transport and transfer properties of photoelectrodes for efficient solar water-splitting.

Copper vacancy activated plasmonic Cu3-xSnS4 for highly efficient photocatalytic hydrogen generation:Broad solar absorption,efficient charge separation and decreased HER overpotential

Broad absorption spectra with efficient generation and separation of available charge carriers are indispensable requirements for promising semiconductor-based photocatalysts to achieve the ultimate goal of solar-to-fuel conversion.Here,Cu_(3-x)SnS_(4)(x=0-0.8)with copper vacancies have been prepared and fabricated via solvothermal process.The obtained copper vacancy materials have extended light absorption from ultraviolet to near-infrared-II region for its significant plasmonic effects.Time-resolved photoluminescence shows that the vacancies can simultaneously optimize charge carrier dynamics to boost the generation of long-lived active electrons for photocatalytic reduction.Density functional theory calculations and electrochemical characterizations further revealed that copper vacancies in Cu_(3-x)SnS_(4)tend to enhance hydrogen’s adsorption energy with an obvious decrease in its H_(2)evolution reaction(HER)overpotential.Furthermore,without any loadings,the H_(2)production rate was measured to be 9.5 mmol·h^(-1)·g^(-1).The apparent quantum yield was measured to be 27%for wavelengthλ>380 nm.The solar energy conversion efficiency was measured to be 6.5%under visible-near infrared(vis-NIR)(λ>420 nm).