Contributions to activity enhancement via Fe incorporation in Ni-(oxy)hydroxide/borate catalysts for near-neutral pH oxygen evolution

Abstract

Ni-borate materials are oxygen evolution catalysts that operate at near-neutral pH and have been found previously to improve due to structural changes induced via anodic conditioning. We find that this increased activity after conditioning at 0.856 V vs. SCE, as measured on a turn-over frequency basis (TOF) at 400 mV overpotential (TOF = 0.38 s(-1)), accompanies significant Fe incorporation (14%). Films conditioned in Fe-free electrolyte exhibit ∼10 times lower activity (TOF = 0.03 s(-1)). By co-depositing Fe-Ni we demonstrate high activity without conditioning (TOF = 0.24 s(-1)) which improves further with shortened (∼30 min) conditioning (TOF = 1.4 s(-1)).

Rate Law Analysis of Water Oxidation and Hole Scavenging on a BiVO4 Photoanode

“…We assume the Faraday efficiency is unity on the dense BiVO4 photoanodes employed in these studies. 31 No impurities, such as trace of Fe or Ni on the electrode surface from the electrolyte, were deposited as catalysts, [32][33][34][35] according to our previous X-ray photoelectron spectroscopy …”

Influence of iron doping on tetravalent nickel content in catalytic oxygen evolving films

“…The behavior of Fe-doped Ni (Fe:Ni) oxide films under basic conditions (1 M KOH) has been revisited (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) and in this recent body of work, the role of Fe in these films has come under debate. X-ray absorption spectra of Fe:Ni oxide films supported by computational studies have led to the contention that Fe 3+ species are the active sites for water oxidation (13).…”

Unusual stoichiometry control in the atomic layer deposition of manganese borate films from manganese bis(tris(pyrazolyl)borate) and ozone

“…34 ALD growth from various bimetallic precursors does not generally replicate the precursor element stoichiometries in the resultant thin films. [35][36][37][38] Given the increasing importance of first row transition metal borates, [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] proposed to arise from the strong oxidizing properties of higher valent manganese oxide layers that are formed upon ozonolysis of surface manganese sites.…”

“…24 For many applications, metal borates must be grown as thin films. Cobalt borate and nickel borate films were electrodeposited from solutions of the metal ions in the presence of borate buffers, [5][6][7][8][9][10][11][12][13][14][15][16] while nanowhiskers of Ni 3 (BO 3 ) 2 were grown on nickel substrates by a molten salt method. 24 Metal borate film growth by gas phase processes is complicated by the high vapor pressure of B 2 O 3 , which makes it generally difficult to control the metal to boron ratios in the thin films at the high temperatures required for growth.…”

“…[1][2][3][4] Recently, first row transition metal borates have emerged as dioxygen (O 2 ) evolution catalysts, [5][6][7][8][9][10][11][12][13][14][15][16] cathode materials in lithium ion batteries, [17][18][19][20][21][22] catalysts for H 2 production by hydrolysis of sodium borohydride, 23 and superhydrophilic Ni 3 (BO 3 ) 2 layers. 24 For many applications, metal borates must be grown as thin films.…”