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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. 

We present an ab initio microkinetic model for the oxidative esterification of 1-propanol to methyl propionate over Pd(111). The model fully accounts for solvation of solution-phase species and added catalytic base and provides key insights into the factors that limit the activity of unpromoted Pd aerobic oxidation catalysts. In particular, we find that the activity is limited by the large steady-state surface H coverage, which destabilizes other adsorbed intermediates via lateral interactions, and substantial barriers governing the formation of O–H bonds, which is required for the reduction of O2 and removal of H byproducts from the catalyst surface.