Influence of Vanadate Structure on Electrochemical Surface Reconstruction and OER Performance of CoV₂O₆ and Co₃V₂O₈

Abstract

Underlying factors responsible for superior phase-dependent electrocatalytic OER activity of crystalline Co-vanadates are investigated. Previous reports on Co-vanadates ascribed activity differences to optimal metal–oxygen bond strength. In contrast, we found etching of vanadate from precatalyst during electrochemical activation to be the primary contributor. The resulting higher surface reconstruction exposes a higher number of catalytically active cobalt sites that otherwise lay inactive due to their position in bulk. Co-vanadates with polymeric vanadates (CoV2O6) showed better OER over monomeric orthovanadates (Co3V2O8) due to higher vanadate etching. Further, this work validates that etching can happen even from lattice positions, where bonding between constituents is strong.

Bias-induced surface reconstruction of a MOF-derived bimetallic (Co & V) oxide as an electrocatalyst for water oxidation

“…However, the leaching, as well as the oxidation of cobalt( ii ) to cobalt( iii ) in the harsh electrochemical environment, increases the surface area and triggers the reconstruction of the catalyst with the self-decoration of highly active cobalt oxyhydroxide (CoOOH) with rich lattice defects at the surface of the annealed products along with the defective Co 2 VO 4 core; thus, we presume that the synergistic effect between the in situ modified surface CoOOH and core Co 2 VO 4 spinel leads to the lowering of overpotential required for the water-oxidation process. 31,32,37 The catalytic activity of CoV@600 toward the oxygen evolution reaction shows higher performance compared to the other catalyst presented in this work and also outperforms many recently published results based on cobalt materials, as shown in Table S6 †. This work emphasizes that the cobalt–vanadium MOF-based precursor-derived bimetallic oxide with the cobalt and vanadium duo present at the two ends of the volcano plot couple together to exhibit improved performance by optimizing the surface energy for the adsorption of OH − .…”

“…31 The ICP-OES studies of the elute of the post catalyst conrmed that almost 70% of vanadium was leached into the solution (Table S5 †), which led to an increase in the surface area of the material and exposed more and more active sites for the catalytic process. 32 As the amorphous vanadium oxides have the least activity toward OER and thereby hinder the catalytic process, leaching leads to the exposure of electrochemically active sites and triggers a self-reconstruction of the annealed MOFs, creating blocks of Co 2 VO 4 nanoparticles interior with a surface decorated defect-rich CoOOH. The XPS spectrum of the post-OER samples presented in Fig.…”

“…Besides this, vanadium-based materials are prone to leaching in an oxidizing environment and therefore they have the tendency to increase the electrochemically active sites, not only the active sites, resulting in the formation defect rich sites induced by the dissolution of vanadium that becomes the hotspot of catalysis. [31][32][33][34] Thus, the development of more active Co/V-based catalysts is encouraged as the duo has the potential to replace noble metal catalysts.…”

Boosting the OER activity of amorphous IrOx in acidic medium by tuning its electron structure using lanthanum salt nanosheets

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15] Oxygen evolution reaction (OER) at the anode is a research focus due to its multi-proton/electron coupling dynamics, determining the overall efficiency of the water-splitting process. 2,5,7,9,[16][17][18][19][20][21][22][23][24][25][26] Much progress has been made in fabricating OER electrocatalysts to reduce the energy barrier. 27 Despite these efforts, it is still necessary to further enhance the catalytic activity of most OER catalysts to reduce their energy consumption for commercial usage.…”

Boosting Surface Reconstruction for the Oxygen Evolution Reaction: A Combined Effect of Heteroatom Incorporation and Anion Etching in Cobalt Silicate Precatalyst

“…[26] The surface transformation is known to initiate at the electrode electrolyte interface and therefore the amount of redox centers taking part in the OER process at the electrode surface is of high significance. The non-redox moiety (often the anionic counterpart) plays a huge role in controlling the extent of surface reconstruction and in this regard phosphate, [27] vanadate, [28] oxalate, [29] phosphide, [30] molybdate, [31] selenide [32] groups have demonstrated excellent OER activity promotion as the nonredox components of Co based (pre)catalysts. Another class of newly emerging anionic counterpart for electrocatalysts is the silicates.…”