A photoanode with plasmonic nanoparticles of earth abundant bismuth for photoelectrochemical reactions.

A wide range of technologies has been developed for producing hydrogen economically and in greener ways. Photoelectrochemical water splitting using photoelectrodes submerged in a bath electrolyte forms a major route of hydrogen evolution. The efficacy of water splitting is improved by sensitizing metal oxide photoelectrodes with narrow bandgap semiconductors that efficiently absorb sunlight and generate and transport charge carriers. Here we show that the efficiencies of photocurrent generation and photoelectrochemical hydrogen evolution by the binary TiO 2 /Sb 2 S 3 anode increase by an order of magnitude upon the incorporation of the earth-abundant plasmonic bismuth nanoparticles into it. The ternary electrode TiO 2 /Bi nanoparticle/Sb 2 S 3 illuminated with sunlight provides us with a photocurrent density as high as 4.21 mA cm -2 at 1.23 V, which is fourfold greater than that of the binary electrode and tenfold greater than that of pristine TiO 2 . By using bismuth nanoparticles, we estimate the incident photon to current conversion efficiency at 31% and solar power conversion efficiency at 3.85%. Here the overall impact of bismuth nanoparticles is attributed to increases in the open-circuit voltage (860 mV), which is by expediting the transfer of photogenerated electrons from Sb 2 S 3 nanoparticles to the TiO 2 electrode, and short-circuit current (9.54 mA cm -2 ), which is by the plasmonic nearfield effect. By combining the cost-effective plasmonic bismuth nanoparticles with the narrow bandgap Sb 2 S 3 on the TiO 2 electrode, we develop a stable, ternary photoanode and accomplish high-efficiency photocurrent generation and hydrogen evolution.