Hydrothermally designed Ag-modified TiO<sub>2</sub> heterogeneous nanocatalysts for efficient hydrogen evolution by photo/electro/photoelectro-chemical water splitting
Mohd Fazil, Norah Alhokbany, Syed Asim Ali, Tokeer Ahmad
Abstract
Abstract One compelling goal of carbon-neutrality is to advance sustainable energy applications through advanced functional nanomaterials for achieving remarkable performance in energy conversion processes, especially in green H 2 energy. Here, Ag-modified TiO 2 nanostructures with highly specific exposed surface sites have been fabricated hydrothermally, elucidating its prominence towards photocatalytic, and photo/-electrocatalytic H 2 production. Further, the as-synthesized nanomaterials were investigated by XRD, electron microscopy (SEM/EDAX/TEM/HRTEM), ICP-MS, PL, Raman, UV-visible DRS, and BET surface area studies. The enhanced activity was established due to the exceptional optoelectronic properties and highly exposed active sites of the Ag-modified TiO 2 nanocatalysts. The photocatalytic activity of 2.5% Ag-doped TiO 2 photocatalyst demonstrated the highest hydrogen evolution, measuring 15.66 mmol <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mtext>g</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mtext>cat</mml:mtext> </mml:mrow> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> with 17.33% apparent quantum yield. Moreover, for photo-electrolysis, 1% and 2.5% Ag-doped TiO 2 nanocatalysts exhibited significantly improved activity with Tafel slopes of 162.49, 87.56 mV dec −1 and onset potentials of 0.77 V (at 1.55 mA cm −2 ), −0.96 V (at 10 mA cm −2 ) for oxygen evolution reaction and hydrogen evolution reaction in alkaline and acidic conditions. Experiments indicated that incorporation of Ag ions in TiO 2 boosted the H 2 evolution due to the extraordinary surface properties and the presence of defect-sides /oxygen vacancies.