Operando Spectroscopic Analysis of CoP Films Electrocatalyzing the Hydrogen-Evolution Reaction

Abstract

Transition metal phosphides exhibit high catalytic activity toward the electrochemical hydrogenevolution reaction (HER) and resist chemical corrosion in acidic solutions. For example, an electrodeposited CoP catalyst exhibited an overpotential, η, of −η < 100 mV at a current density of −10 mA cm −2 in 0.500 M H 2 SO 4 (aq). To obtain a chemical description of the material asprepared and also while effecting the HER in acidic media, such electrocatalyst films were investigated using Raman spectroscopy and X-ray absorption spectroscopy both ex situ as well as under in situ and operando conditions in 0.500 M H 2 SO 4 (aq). Ex situ analysis using the tandem spectroscopies indicated the presence of multiple ordered and disordered phases that contained both near-zerovalent and oxidized Co species, in addition to reduced and oxygenated P species. Operando analysis indicated that the active electrocatalyst was primarily amorphous and predominantly consisted of near-zerovalent Co as well as reduced P.

Stability of CoPx Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water

“…Figure S2c). The Raman peaks, which we attributed to CoP x , match with the Raman spectrum of electrodeposited CoP/CoP x O y mixed electrodes reported by Saadi et al . There, the question of the exact composition of the Raman‐active phase remained unanswered.…”

“…Moreover, it was also found that an increasing P/metal ratio of TMP yields an increase in HER performance which is also reflected in decreasing Tafel slopes ,,. Thus, transition metal phosphides, including nickel phosphides, cobalt phosphides, iron phosphides, molybdenum phosphides,,, tungsten phosphides,, copper phosphides and their alloys have emerged as potential HER electrocatalysts. In order to increase the apparent electrochemical activity, porous conductive substrates such as carbon cloths and nickel foams are often used as current collectors.…”

A Janus Nickel Cobalt Phosphide Catalyst for High‐Efficiency Neutral‐pH Water Splitting

“…Communications previously. [20] Thel ower white-line amplitude for Ni 0.1 Co 0.9 Ps uggests an increase in the Co oxidation state after the Ni addition, which is in agreement with the first derivative analysis (Figure S34), [21] XPS results (Figure 3a)a nd l-edge measurements ( Figure S35 to S37). From XANES,t he higher intensity of Co Kp re-edge peak of Ni 0.1 Co 0.9 Pd emonstrates the electron transfer caused by Ni addition, analogous to aprior report on Co 0.1 Fe 0.9 Scatalyst.…”

Multifunctional Transition Metal‐Based Phosphides in Energy‐Related Electrocatalysis

“…The metal phosphides can be facilely deposited onto the conductive substrate surfaces by the reduction reaction of metal ions and H 2 PO 2 − . In general, this method is only applicable to the synthesis of specific metal phosphides, such as CoP, NiP, and the yielded metal phosphides mainly present amorphous features and complex composition …”