Anion-exchange membrane fuel cells provide the possibility to use platinum group metal-free catalysts, but the anodic hydrogen oxidation reaction (HOR) suffers from sluggish kinetics and its source is still debated. Here, over nickel-tungsten (Ni-W) alloy catalysts, we show that the Ni:W ratio greatly governs the HOR performance in alkaline electrolyte. Experimental and theoretical studies unravel that alloying with W can tune the unpaired electrons in Ni, tailoring the potential of zero charge and the catalytic surface to favor hydroxyl adsorption (OHad). The OHad species coordinately interact with potassium (K+) ions, which break the K+ solvation sheath to leave free water molecules, yielding an improved connectivity of hydrogen-bond networks. Consequently, the optimal Ni17W3 alloy exhibits alkaline HOR activity superior to the state-of-the-art platinum on carbon (Pt/C) catalyst and operates steadily with negligible decay after 10,000 cycles. Our findings offer new understandings of alloyed HOR catalysts and will guide rational design of next-generation catalysts for fuel cells.
Supported ordered intermetallic compounds exhibit superior catalytic performance over their disordered alloy counterparts in diverse reactions. But the synthesis of intermetallic compounds catalysts often requires high-temperature annealing that leads to the sintering of metals into larger crystallites. Herein, we report a small molecule-assisted impregnation approach to realize the general synthesis of a family of intermetallic catalysts, consisting of 18 binary platinum intermetallic compounds supported on carbon blacks. The molecular additives containing heteroatoms (that is, O, N, or S) can be coordinated with platinum in impregnation and thermally converted into heteroatom-doped graphene layers in high-temperature annealing, which significantly suppress alloy sintering and insure the formation of small-sized intermetallic catalysts. The prepared optimal PtCo intermetallics as cathodic oxygen-reduction catalysts exhibit a high mass activity of 1.08 A mgPt-1 at 0.9 V in H2-O2 fuel cells and a rated power density of 1.17 W cm-2 in H2-air fuel cells.
