Parallelized Screening of Characterized and DFT-Modeled Bimetallic Colloidal Cocatalysts for Photocatalytic Hydrogen Evolution

Abstract

Using a newly designed and developed parallelized photoreactor and colorimetric detection method, a large sampling of bimetallic cocatalysts (Pd/Sn, Pd/Mo, Pd/Ru, Pd/Pb, Pd/Ni, Ni/Sn, Mo/Sn, and Pt/Sn) for photocatalytic water reduction have been tested. Of these cocatalysts, the combination of palladium and tin showed the highest synergistic behavior and peak hydrogen gas production at a low relative fraction of palladium. The resulting palladium/tin bimetallic cocatalysts were characterized, and specifically, and scanning transmission electron microscopy energy-dispersive X-ray spectroscopy indicated that palladium and tin elements reside within the same particle. The experimental catalytic activity for the palladium/tin mixture was compared to density functional theory-derived energy values associated with the adsorption of hydrogen onto a surface. This comparison demonstrated that the typical peak found in electrochemical Sabatier volcano plots at ΔG H* = ∼0 eV were replicated in the experimental photocatalytic system with a peak activity observed at ΔGH* = −0.036 eV. Computational confirmation of the results expressed here demonstrates the efficacy of colorimetric detection of hydrogen in parallel and presents a model for increasingly rapid catalyst screening.

Ligand Enhanced Activity of In Situ Formed Nanoparticles for Photocatalytic Hydrogen Evolution

“…Our first series of experiments established the HER photocatalytic performance of in situ formed NPs of three metal compositions, (100 % Au, 75/25 Au/Cu, and 50/50 Au/Cu) using our previously reported photoreactor system. [51] A Au/Cu system was chosen because the composition and atomic arrangement of both mono-and bimetallic NPs containing these metals are relatively well understood, [57][58][59] and the combination of these metals mitigates issues of faceting, oxidation, and NP degradation, which are factors that could convolute interpretation of H 2 production. [54,55] In a typical experiment, each reaction well contained PS, TEOA, DMSO, water, and 1 mM total metal salt added in the various molar ratios.…”

“…Previous experiments on the quantification limits of the tape detection method suggest that H 2 production above 2 μmol can be considered active. [51] For in situ formed catalysts, some catalytic activity was measured during the first round of irradiation for all three compositions. By the third round, however, all compositions were catalytically inactive (Figure 2A-C).…”

“…[52,53] Briefly, quantification is achieved by generating a calibration curve using known amounts of H 2 in the reaction wells and recording the corresponding changes in detection tape color using a digital camera, where well colors are then translated to RGB values via Wolfram Mathematica code (see supporting information for full details and code). [51] Using this calibration, we have demonstrated that H 2 generation can be monitored in real time, at each well, simply by analyzing the RGB values extracted from optical images taken throughout the reaction. [51] Once the H 2 produced in each well is determined, notable wells, such as those that define a trend of interest, can be fully characterized to determine NP characteristics.…”

“…[51] Using this calibration, we have demonstrated that H 2 generation can be monitored in real time, at each well, simply by analyzing the RGB values extracted from optical images taken throughout the reaction. [51] Once the H 2 produced in each well is determined, notable wells, such as those that define a trend of interest, can be fully characterized to determine NP characteristics. For example, our previous work using this reactor system showed that bimetallic NPs can be synthesized in situ using an iridium-based PS and triethanolamine (TEOA) as the SR.…”

Insights into Hydrogen Evolution Reaction on 2D Transition Metal Dichalcogenides

“…Twodimensional transition metal dichalcogenides (2D-TMDs) have received considerable interest as promising non-precious electrocatalysts for hydrogen evolution reaction (HER) in acidic media. [1][2][3] Based on density functional theory (DFT) calculations and using the fact that the hydrogen adsorption free energy (∆GH) is a good descriptor of HER activity for transition metals, [4][5][6][7][8][9][10][11] Hinnemann et al 12 first proposed that the Mo edge site of MoS2 would be active for HER, which was later extensively verified in experiments. [13][14][15][16][17][18][19] A large number of works have since then explored not only MoS2 but also other 2D-TMDs, phosphides, carbides as HER catalysts.…”