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Abstract Developing efficient and stable earth-abundant electrocatalysts for acidic oxygen evolution reaction is the bottleneck for water splitting using proton exchange membrane electrolyzers. Here, we show that nanocrystalline CeO 2 in a Co 3 O 4 /CeO 2 nanocomposite can modify the redox properties of Co 3 O 4 and enhances its intrinsic oxygen evolution reaction activity, and combine electrochemical and structural characterizations including kinetic isotope effect, pH- and temperature-dependence, in situ Raman and ex situ X-ray absorption spectroscopy analyses to understand the origin. The local bonding environment of Co 3 O 4 can be modified after the introduction of nanocrystalline CeO 2 , which allows the Co III species to be easily oxidized into catalytically active Co IV species, bypassing the potential-determining surface reconstruction process. Co 3 O 4 /CeO 2 displays a comparable stability to Co 3 O 4 thus breaks the activity/stability tradeoff. This work not only establishes an efficient earth-abundant catalysts for acidic oxygen evolution reaction, but also provides strategies for designing more active catalysts for other reactions.

Electrochemical synthesis of hydrogen peroxide (H 2 O 2 ) in acidic solution can enable the electro-Fenton process for decentralized environmental remediation, but robust and inexpensive electrocatalysts for the selective two-electron oxygen reduction reaction (2e − ORR) are lacking. Here, we present a joint computational/experimental study that shows both structural polymorphs of earth-abundant cobalt diselenide (orthorhombic o -CoSe 2 and cubic c -CoSe 2 ) are stable against surface oxidation and catalyst leaching due to the weak O* binding to Se sites, are highly active and selective for the 2e − ORR, and deliver higher kinetic current densities for H 2 O 2 production than the state-of-the-art noble metal or single-atom catalysts in acidic solution. o -CoSe 2 nanowires directly grown on carbon paper electrodes allow for the steady bulk electrosynthesis of H 2 O 2 in 0.05 M H 2 SO 4 with a practically useful accumulated concentration of 547 ppm, the highest among the reported 2e − ORR catalysts in acidic solution. Such efficient and stable H 2 O 2 electrogeneration further enables the effective electro-Fenton process for model organic pollutant degradation.

The development of efficient and robust earth‐abundant electrocatalysts for the oxygen evolution reaction (OER) is an ongoing challenge. Here, a novel and stable trimetallic NiFeCr layered double hydroxide (LDH) electrocatalyst for improving OER kinetics is rationally designed and synthesized. Electrochemical testing of a series of trimetallic NiFeCr LDH materials at similar catalyst loading and electrochemical surface area shows that the molar ratio Ni:Fe:Cr = 6:2:1 exhibits the best intrinsic OER catalytic activity compared to other NiFeCr LDH compositions. Furthermore, these nanostructures are directly grown on conductive carbon paper for a high surface area 3D electrode that can achieve a catalytic current density of 25 mA cm⁻²at an overpotential as low as 225 mV and a small Tafel slope of 69 mV dec⁻¹in alkaline electrolyte. The optimized NiFeCr catalyst is stable under OER conditions and X‐ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, and elemental analysis confirm the stability of trimetallic NiFeCr LDH after electrochemical testing. Due to the synergistic interactions among the metal centers, trimetallic NiFeCr LDH is significantly more active than NiFe LDH and among the most active OER catalysts to date. This work also presents general strategies to design more efficient metal oxide/hydroxide OER electrocatalysts.