Amorphous outperforms crystalline nanomaterials: surface modifications of molecularly derived CoP electro(pre)catalysts for efficient water-splitting

Abstract

The single source precursor (SSP) approach was used to prepare highly active CoP bifunctional electro(pre) catalysts for the oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and overall water splitting (OWS) reaction starting from a molecular b-diketiminato Co(I) cyclo-P 4 complex. Crystalline or amorphous CoP particles were attained depending on the preparation route. Notably, the amorphous CoP displayed higher activity compared to the crystalline CoP on nickel foam (NF) and fluorinated tin oxide (FTO) substrates due to its unique electronic properties and surface characteristics. During the OER, severe oxidation to Co-oxy(hydroxides)/oxides by the loss of P was found to be crucial to increase the concentration of CoO x active sites. Interestingly, complete leaching of surface P from CoP and surface Co enrichment occurred during the HER. Finally, an OWS device was fabricated where the amorphous CoP outperformed the crystalline CoP with respect to low OWS cell voltage (with a difference of 130 mV) and enhanced stability for 5 days.

Stannites – A New Promising Class of Durable Electrocatalysts for Efficient Water Oxidation

“…All impedance spectra were fitted using an equivalent RC circuit model. The charge‐transfer resistance ( R ct ) was then obtained from the diameter of the semicircle in the Nyquist plots …”

“…Electrophoretic deposition . The investigated materials were deposited electrophoretically by a well‐established method on both, NF and FTO . A potential difference of 10 V, using FTO as both counter and reference electrode or NF for both, in a mixture of iodine and acetone on a 1×1 cm 2 area was applied.…”

“…[79][80][81] The ECSA of the catalysts can be calculated using the equation ECSA = C dl /C s, where C s can be defined as the specific capacitance of the material per unit area under identical electrolyte conditions. [82] Therefore, the ECSA is directly proportional to C dl .…”

“…The charge-transfer resistance (R ct ) was then obtained from the diameter of the semicircle in the Nyquist plots. [79,82] Electrophoretic deposition. The investigated materials were deposited electrophoretically by a well-established method on both, NF and FTO.…”

“…The investigated materials were deposited electrophoretically by a well-established method on both, NF and FTO. [62,75,[82][83][84] A potential difference of 10 V, using FTO as both counter and reference electrode or NF for both, in a mixture of iodine and acetone on a 1 × 1 cm 2 area was applied. The electric charge on the catalyst in acetone is insufficient for EPD, as very small amounts of free ions exist in acetone.…”